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Management intensity effects on animal performance and herbage response in bahiagrass pastures

University of Florida Institutional Repository
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PAGE 1

MANAGEMENT INTENSITY EFFECT S ON ANIMAL PERFORMANCE AND HERBAGE RESPONSE IN BAHIAGRASS PASTURES By R. LAWTON STEWART, JR. A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2003

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Copyright 2003 by R. Lawton Stewart, Jr.

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To my wife Beth.

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ACKNOWLEDGMENTS The author would like to begin by thanking Dr. Lynn E. Sollenberger, chairman of the supervisory committee and mentor. His guidance and direction throughout the graduate school programs and the writing of this thesis have been greatly appreciated. Also thanks go to the rest of the advisory committee, Dr. Martin B. Adjei, Dr. Carrol G. Chambliss, and Dr. Adegbola Adesogan, for their willingness to serve on the graduate committee, thoughtful input, and for reviewing the thesis. Thanks are also due to many who assisted in both field and lab tasks. They include fellow graduate students Jos Dubeux and Joa Vendramini, who spent hours upon hours at the Beef Research Unit helping collect data, Sid Jones and Dwight Thomas, at the Forage Evaluation Field Laboratory, for providing valuable help with field exercises, and Richard Fethiere and the crew of the Forage Evaluation Support Laboratory, for assistance in sample analysis. Dr. Yoana C. Newman provided excellent advice on topics ranging from field techniques to statistical analyses. Also thanks are expressed to Dr. Jerry M. Bennett, department chair, and Dr. David S. Wofford, graduate coordinator, for the opportunity to study in the Agronomy Department. Thanks are due to fellow graduate students Deke Alkire, Nathan and Wimberley Krueger, Brad Austin, Sindy Interrante, Paul Davis, Marca Grise, and others for their help, but more importantly for their friendship over the past two years. Last, but not least, the author would like to thank his family. His wife, Beth, was supportive of his decisions and many tasks throughout graduate school. Also, his parents, iv

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Robert and Martha Stewart, have always emphasized the importance of education and have been encouraging throughout the many educational processes. Also thanks go to the two best sisters in the world, Kate and Sally. v

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TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES...........................................................................................................viii LIST OF FIGURES.............................................................................................................x ABSTRACT.......................................................................................................................xi CHAPTER 1 INTRODUCTION........................................................................................................1 2 LITERATURE REVIEW.............................................................................................5 Characteristics of Bahiagrass........................................................................................5 General..................................................................................................................5 Yield......................................................................................................................6 Nutritive Value......................................................................................................7 Animal Performance..............................................................................................8 Nitrogen Fertilization....................................................................................................9 Cool-Season and Native Grasses...........................................................................9 Tropical Grasses..................................................................................................11 Bahiagrass............................................................................................................14 Environmental Implications................................................................................15 Grazing Management..................................................................................................16 Grazing Method...................................................................................................16 Grazing Frequency..............................................................................................18 Grazing Intensity.................................................................................................20 Summary.....................................................................................................................22 3 HERBAGE AND ANIMAL PERFORMANCE RESPONSES TO MANAGEMENT INTENSITY OF CONTINUOUSLY STOCKED BAHIAGRASS PASTURES......23 Introduction.................................................................................................................23 Methods and Materials...............................................................................................24 Experimental Site................................................................................................24 Treatments and Design........................................................................................25 Pasture and Animal Management........................................................................26 Pasture Responses...............................................................................................29 vi

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Animal Responses...............................................................................................31 Statistical Analysis..............................................................................................31 Results and Discussion...............................................................................................32 Herbage Mass......................................................................................................33 Herbage Accumulation Rate................................................................................34 Crude Protein.......................................................................................................40 In Vitro Organic Matter Digestibility..................................................................44 Herbage Allowance.............................................................................................47 Average Daily Gain.............................................................................................49 Gain per Hectare..................................................................................................53 Bahiagrass Cover.................................................................................................55 Summary and Conclusions.........................................................................................56 4 GRAZING METHOD EFFECTS ON FORAGE GROWTH AND NUTRITIVE VALUE OF BAHIAGRASS PASTURES.................................................................58 Introduction.................................................................................................................58 Methods and Materials...............................................................................................59 Experiment Site...................................................................................................59 Treatments and Design........................................................................................59 Pasture Measurements.........................................................................................61 Statistical Analyses..............................................................................................62 Results and Discussion...............................................................................................62 Herbage Accumulation Rate................................................................................62 Crude Protein.......................................................................................................65 In Vitro Organic Matter Digestibility..................................................................68 Bahiagrass Cover.................................................................................................70 Summary and Conclusions.........................................................................................71 5 SUMMARY AND CONCLUSIONS.........................................................................73 LIST OF REFERENCES...................................................................................................78 BIOGRAPHICAL SKETCH.............................................................................................84 vii

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LIST OF TABLES Table page 3-1 List of actual stocking rates (SR) of continuously stocked bahiagrass pastures....26 3-2 Rainfall at the experiment site for years 2001-2002 and the 30-yr average for Gainesville, FL.......................................................................................................27 3-3 Nitrogen application dates on continuously stocked bahiagrass pastures.............28 3-4 Composition of mineral supplement......................................................................28 3-5 Herbage mass double sample regression equations...............................................30 3-6 Monthly temperatures at the experiment site for years 2001-2002.......................32 3-7 Pasture herbage mass (HM) and herbage accumulation rate (HAR) responses to management intensity of continuously stocked bahiagrass pastures.....................34 3-8 Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD) responses to management intensity of continuously stocked bahiagrass pastures..................................................................................................................41 3-9 Herbage allowance response to management intensity.........................................49 3-10 Heifer average daily gain (ADG) and gain per hectare (GPH) responses to management intensity............................................................................................51 4-1 Nitrogen application dates and rates for bahiagrass pastures................................59 4-2 Herbage accumulation rate (HAR ) response to grazing method on bahiagrass pastures..................................................................................................................63 4-3 Seasonal pasture herbage accumulation rate (HAR ) response to grazing method on bahiagrass pastures............................................................................................64 4-4 Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD) responses to stocking method on bahiagrass pastures...........................................66 4-5 Seasonal herbage crude protein (CP) response to grazing method on bahiagrass pastures..................................................................................................................67 viii

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4-6 Seasonal herbage in vitro organic matter digestibility (IVOMD) response to grazing method on bahiagrass pastures..................................................................69 4-7 Changes in bahiagrass cover in response to grazing method in bahiagrass pastures..................................................................................................................70 ix

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LIST OF FIGURES Figure page 3-1 Herbage mass (HM) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001.................................................35 3-2 Herbage mass (HM) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002.................................................36 3-3 Herbage accumulation rate (HAR) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001.............................38 3-4 Herbage accumulation rate (HAR) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002.............................39 3-5 Herbage crude protein (CP) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001.................................................42 3-6 Herbage crude protein (CP) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002.................................................43 3-7 Herbage in vitro organic matter digestibility (IVOMD) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001...45 3-8 Herbage in vitro organic matter digestibility (IVOMD) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002...46 3-9 Herbage allowance (HA) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001.................................................48 3-10 Herbage allowance (HA) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002.................................................50 3-11 Yearling beef heifer cumulative average daily gain (ADG) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001........................................................................................................................52 3-12 Yearling beef heifer cumulative average daily gain (ADG) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002........................................................................................................................54 x

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science MANAGEMENT INTENSITY EFFECTS ON ANIMAL PERFORMANCE AND HERBAGE RESPONSE IN BAHIAGRASS PASTURES By R. Lawton Stewart, Jr. August 2003 Chairman: Lynn E. Sollenberger Major Department: Agronomy Bahiagrass (Paspalum notatum Flgge) pasture covers approximately one million hectares in Florida, 90% of which is utilized by beef cattle. Urbanization may force beef producers to achieve economic livelihood on reduced land area. One option for producers is to increase intensity of management of the remaining pasture resource. The objectives of this research were 1) to evaluate the effects of management intensity (MI), defined as combinations of N fertilization and stocking rates (SR), on yearling beef heifer and bahiagrass pasture performance (Exp. 1), and 2) to evaluate bahiagrass forage responses to continuous and rotational stocking (Exp. 2). Treatments in Exp. 1 included LOW (40 kg N ha -1 yr -1 1.2 animal units [AU, one AU=500 kg live weight] ha -1 SR), MODERATE (120 kg N ha -1 yr -1 2.4 AU ha -1 SR), and HIGH MI (360 kg N ha -1 yr -1 3.6 AU ha -1 SR). Treatments in Exp. 2 were continuous stocking, and rotational stocking with 1-, 3-, 7-, and 21-d grazing periods. All rotational treatments had a 21-d rest period. xi

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Herbage mass (3.0 Mg ha -1 ) and herbage allowance (4.0 kg forage kg -1 animal weight) in Exp. 1 were greater for LOW and decreased as MI increased to HIGH (2.6 Mg ha -1 and 1.1 kg forage kg -1 animal weight). This occurred despite herbage accumulation rate being greater for HIGH (33 kg ha -1 d -1 ) than LOW (19 kg ha -1 d -1 ). Nutritive value increased with increasing MI, in part because of greater N rate and also because the higher stocking rates likely increased the frequency at which cattle revisited grazing locations. Average daily gain decreased from LOW to HIGH (0.46 to 0.36 kg d -1 ) because of the decrease in herbage allowance for HIGH. Gain per hectare increased with increasing MI due to a greater utilization of the forage present. Bahiagrass cover increased with the HIGH MI (7.1%) and decreased with LOW (-6.4) and MODERATE (-4.7%). Decreases in cover were associated with the invasion of vaseygrass (Paspalum urvillei) and smutgrass (Sporobolus indicus) and occurred because of decreased grazing pressure that allowed these species to mature and become unpalatable to cattle. In Exp. 2, rotational stocking increased herbage accumulation rate and digestibility over continuous stocking, but it had no effect on herbage crude protein. Continuous stocking resulted in greater bahiagrass cover, while rotational stocking led to reduced cover due to the encroachment of vaseygrass and smutgrass. These experiments demonstrated increased bahiagrass production and quality with increasing management intensity. However, the magnitude of these improvements is not sufficient to compensate for the additional costs associated with greater management intensity above MODERATE and the greater risk of damage to the environment. Therefore, if the need for increased production per unit land area becomes acute, the use of another more management-responsive grass species likely will be required. xii

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CHAPTER 1 INTRODUCTION Grasslands occupy large areas of Florida and the southeastern USA and serve as an important source of feed to the livestock industry. In the state of Florida, the human population has grown significantly over the past 40 yr, from approximately five million people in 1960 to approximately sixteen million in 2000 (U.S. Census Bureau, 2002). This three-fold increase has led to a large increase in urbanization and associated loss of area devoted to grasslands. Current projections are that population will increase to twenty-four million by 2030 (Arndorfer, 2003). In the future, producers may be faced with land constraints and may need to consider intensification of grassland management as a means of maintaining overall production on a decreasing land resource. Changes in management intensity could include greater nitrogen (N) fertilization and stocking rates and use of rotational stocking. These changes have the potential to affect productivity and profitability of the system; however, some may also increase the potential for negative environmental impact. Before increasing management intensity can be recommended, its impact on the environment and on plant and animal performance must be determined. The beef industry is a vital component of Floridas large agriculture industry. In 2001 Florida had a total of 975,000 beef cows; this ranks twelfth in the nation and third for states east of the Mississippi River. Revenues from the beef cattle industry in Florida totaled 371 million dollars in 2000, accounting for 5.3% of the states total agricultural cash receipts (Florida Dept. of Agriculture, 2002). 1

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2 Bahiagrass (Paspalum notatum Flgge) is an essential resource to the beef industry in Florida. It is the most widely planted grass in the state, covering approximately one million hectares. Of this area, 90% is grazed by beef cattle (Chambliss, 2000). Bahiagrass is an aggressive grass that is relatively tolerant of drought and low fertility soils (Prates et al., 1975). This makes bahiagrass well adapted to the range of environmental conditions in Florida. The most widely distributed bahiagrass cultivar is Pensacola, and it is known for its relatively high yields and moderate animal performance (Chambliss, 2000). Nitrogen is generally the most limiting nutrient for bahiagrass growth (Gates et al., 2004), and research has shown a potentially large increase in production and forage N concentration with increasing N rate (Blue, 1988). Thus, there is potential to achieve greater livestock production on bahiagrass by increasing N fertilization rate. Stocking method plays an important role in grazing systems. Because of its grazing tolerance and to minimize cost of production, many bahiagrass pastures in Florida are continuously stocked during the summer grazing season. Rotational stocking generally allows for a higher stocking rate and higher gains per unit land area (Blaser, 1986), so potential exists to increase livestock production per hectare on bahiagrass pastures by using rotational stocking. Stocking rate is the relationship between number of animals and the area of pasture to which they are assigned over an extended period of time. Stocking rate is generally considered to be the most important grazing management decision because it has a major impact on both forage production and performance of grazing animals (Matches, 1992). Increasing stocking rate improves the consumption of available herbage per hectare of grassland, often decreasing individual animal production but increasing animal

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3 production per hectare (Burns et al., 2003). Thus, stocking rate is a powerful tool influencing production of a given area of grassland. The thesis research that was conducted was part of a larger project that evaluated nutrient dynamics and cycling, animal grazing behavior, pasture characteristics, and animal performance on grazed bahiagrass. The particular areas of focus in the research reported herein are animal performance and pasture attributes of grazed bahiagrass pastures managed at different intensities (defined by stocking rate, N fertilizer rate, and grazing method). The research was divided into two experiments. The first experiment evaluated animal performance and forage response of continuously stocked bahiagrass pastures using three treatments that were defined by stocking rate and N fertilizer rate. Animal performance was measured as average daily gain of yearling beef heifers and weight gain per unit land area. Forage responses measured included nutritive value, herbage mass, herbage allowance, and herbage accumulation. From these data the relationships between heifer daily gain and bahiagrass herbage mass and bahiagrass herbage allowance were determined. Results from this study will help to assess the extent to which increasing management intensity (stocking rate and N fertilization) of bahiagrass pasture increases pasture and animal performance. The second experiment evaluated forage responses to four rotational stocking and one continuous stocking treatment on bahiagrass pasture. The rotational treatments were defined by length of the grazing period and all had the same rest period. Forage responses measured include nutritive value, herbage mass, herbage accumulation, and bahiagrass cover. These data will allow comparison of bahiagrass pasture characteristics

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4 across a wide range of grazing methods and allow conclusions to be drawn about the potential for increasing bahiagrass pasture performance by changing grazing method. Data from these experiments are useful from several perspectives. Producers can use them to make informed management decisions. In addition, this research furthers the understanding of intensive management and its effect on animal performance and herbage response. Scientists can use these data to guide future research and to develop models related to intensified management. In summary, this research is relevant to the agricultural industry as it explores options for maintaining sustainability in an increasingly urbanized community, and to the rest of society as it evaluates possible environmental and economic impacts of management strategies.

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CHAPTER 2 LITERATURE REVIEW Characteristics of Bahiagrass General Bahiagrass (Paspalum notatum Flgge) originated in Brazil and northern Argentina and was introduced to the southeastern USA in the early 1900s. It has spread extensively in the southeast and is grown throughout Florida for pasture, turf, and hay (Chambliss, 2000). Bahiagrass is the most widely planted perennial pasture grass in Florida, covering more than one million hectares (Chambliss, 2000), and is extensively utilized by the states beef industry which numbers 975,000 cows (Florida Dept. of Agriculture, 2002). Bahiagrass is a warm-season, deep-rooted, perennial grass that forms a dense, thick sod from an extensive root and rhizome system (Burson and Watson, 1995). This morphology makes it less prone to encroachment from other grasses and weeds. Bahiagrass is characterized by horizontal stems at the soil surface, and purple leaf sheaths (Gates et al., 2004). Leaf blades are flat or slightly folded, 3 to 12 cm wide and can grow from 3 to 30 cm long. Bahiagrass is also characterized by a tall raceme inflorescence (Gates et al., 2004). Bahiagrass is aggressive and well acclimated to the variety of environmental conditions throughout Florida (Prates et al., 1975). It can persist in both well-drained and low-lying, poorly drained soils. Adapted to the southern USA Coastal Plain region, bahiagrass performs best in sandy soils with a pH of 5.5 to 6.5 (Twidwell et al., 1998). Except for highly infertile sites, nutrients needed for adequate growth are limited to N 5

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6 (Gates et al., 2004). Bahiagrass is also resilient to pressure from most pests. The only major pest problem is the recent emergence of the mole cricket (Scapteriscus sp.), which can destroy pasture stands by damaging the root system. Fall armyworms (Spodoptera frugiperda) can also defoliate stands, but usually only during seasons when more preferred forages are not available (Burson and Watson, 1995). Bahiagrass has the C 4 photosynthetic metabolism and responds to high temperature and moisture. Pensacola bahiagrass exhibits little growth under 15C, which limits the length of its productive period in Florida to April to late October (Mislevy, 1985). During the spring growing season, bahiagrass is characterized by high nutritive value and low forage production. This can be attributed to drought and to lower temperatures which depress plant respiration, preserving nonstructural carbohydrates, and decreased lignification resulting in greater cell wall digestiblility (Blaser, 1986). During the peak of the growing season from July to early September, pastures produce higher herbage masss and digestibility decreases. Performance of animals grazing bahiagrass follows a similar pattern, with gains being higher in the early growing season, peaking, and then leveling off or decreasing later in the growing season (Twidwell et al., 1998). Yield Forages for production systems should ideally be high yielding and high in nutritive value to support exceptional animal performance. Pensacola bahiagrass is highly tolerant of many unfavorable conditions such as overgrazing; however, it is also known as a low nutritive value forage with lower than average herbage yield among the adapted warm-season perennial grasses (Sollenberger, 2001). Cuomo et al. (1996) conducted a study of plant morphology and nutritive value of three bahiagrassses (Pensacola, Argentine, and Tifton 9) as affected by harvest frequency. They found no

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7 differences among cultivars in herbage production, and means were 11.2 Mg ha -1 for Argentine, 11.9 Mg ha -1 for Pensacola, and 11.8 Mg ha -1 for Tifton 9. Differences were obvious during the month of May when Argentine produced 1.9 Mg ha -1 as compared to higher values of 3.1 and 2.9 Mg ha -1 by Pensacola and Tifton 9, respectively. Under high rates of N fertilizer (450 to 700 kg ha -1 ), bahiagrass yields up to 15.6, 15.1, and 19.9 Mg ha -1 have been reported in various states in the southeastern USA (Stanley, 1994; Burton et al., 1997; Twidwell et al., 1998). Nutritive Value Cuomo et al. (1996) found Pensacola to contain a neutral detergent fiber (NDF) concentration of 657 g kg -1 as compared to 642 g kg -1 for Argentine bahiagrass and 640 g kg -1 in Tifton 9 bahiagrass over a growing season. In this study acid detergent fiber (ADF) and lignin were similar for the three grasses, and averaged 323 and 44 g kg -1 respectively. Muchovej and Mullahey (2000) reported NDF values over a growing season to be higher; Pensacola NDF was 790 g kg -1 as compared to 783 and 787 g kg -1 for Argentine and Tifton 9, respectively. The in vitro true digestibility (IVTD) of Pensacola (588 g kg -1 ) was comparable to that of Argentine (589 g kg -1 ) but was lower than Tifton 9 (598 g kg -1 ) with an N rate of 336 kg ha -1 (Cuomo, 1996). However, Muchovej and Mullahey (2000) found Pensacola IVTD to be similar to Tifton 9 (510 and 508 g kg -1 respectively) with an N rate of 56 kg ha -1 Crude protein (CP) of Pensacola and Tifton 9 were identical, 113 g kg -1 but they were slightly lower than that of the Argentine (118 g kg -1 ; Cuomo, 1996). Under clipping management, Muchovej and Mullahey (2000) found no significant differences in Pensacola CP values over the growing season (average of 96 g kg -1 ).

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8 Cuomo et al. (1996) also compared NDF and lignin concentrations of different plant parts (leaf, stem, and whole plant) for the three bahiagrass cultivars over the entire growing season. They found stem, leaf, and whole-plant NDF to be higher in Pensacola (646, 701, and 660 g kg -1 respectively) than Tifton 9 (636, 669, and 640 g kg -1 ). Lignin was also slightly higher in Pensacola than Tifton 9 (40, 59, 44 g kg -1 versus 37, 54, and 41 g kg -1 respectively). Nutritive value of grazed bahiagrass declines over the growing season due to high temperature and accumulation of mature material and reproductive structures. Utley et al. (1974) reported IVOMD of 679 g kg -1 for bahiagrass clipped in May compared to 429 g kg -1 in late September. Cuomo also found a decrease in in vitro organic matter digestibility (IVOMD) across the season with values of 629 g kg -1 in late May and 562 g kg -1 in early September at 20-d harvests intervals. Crude protein decreased from 139 to 110 g kg -1 over the same period, while NDF, ADF, and lignin increased from late May to early September (629 to 657, 302 to 328, and 38 to 47 g kg -1 respectively). Animal Performance In livestock operations, animal performance is the essential goal. Bahiagrass is known to withstand heavy grazing and poor growing environments; however, it is also known for its average to lower than average animal performance. This is particularly a problem in Florida during hot summer months when cattle are under stress and sometimes have negative average daily gains (ADG). In a study by Prates et al. (1975) ADG was measured monthly on continuously stocked Pensacola bahiagrass from May through October. This study utilized the put and take system to adjust stocking rate, and fertilizer was applied at 193 kg ha -1 yr -1 of elemental N. They reported ADG to be 1.00 kg d -1 in May; however, ADG steadily declined to -0.52 kg d -1 in September with only a

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9 slight increase to 0.15 kg d -1 in October. Also in this study, gain ha -1 was measured in each month. In May, cattle gained 122 kg ha -1 They lost 97 kg ha -1 in September, and gained 10 kg ha -1 in October. Twidwell et al. (1998) reported ADG of steers grazing Pensacola bahiagrass pastures to be 0.43 kg compared to 0.49 kg for steers grazing Coastal bermudagrass [Cynodon dactylon (L.)] over a 4-yr grazing trial. Additional animal performance data will be discussed later in the literature review as it relates to specific management practices. Nitrogen Fertilization Cool-Season and Native Grasses Research has shown that C 3 grasses have the potential to respond to N application. Tall fescue (Festuca arundinacea Schreb.) is grown in many areas of the temperate USA. Moyer et al. (1995) evaluated forage production and N concentration of fescue at three N application rates: 13, 112, and 168 kg ha -1 As N rates increased, forage DM production increased from 3.26 to 4.11 to 4.49 Mg ha -1 respectively. At these N rates, forage CP concentrations were 140, 176, and 194 g kg -1 respectively, showing a significant increase as N rate increased. Zhang et al. (1995) evaluated annual ryegrass (Lolium multiflorum L.) N and N constituents. In this study, total N increased from 29.8 to 50.4 g kg -1 as N application increased from 0 to 224 g kg -1 Also it was reported that as N fertilization increased, ADF-bound N, as a constituent of total N, decreased from 7.63 to 3.41 g kg -1 From this it is concluded that increasing N application can decrease ADF-bound N in addition to increasing N concentration in forages. Texas bluegrass (Poa arachnifera Torr.) is a cool-season perennial grass used for pasture in the southern Great Plains. Pitman et al. (2000) evaluated the response of

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10 bluegrass to N fertilization rates of 0 and 100 kg N ha -1 At these levels, forage yields across 2 yr were 1.8 and 4.1 Mg ha -1 respectively. Native range grasses also are an important part of many forage production systems. Lorenz and Rogler (1972) evaluated response of a mixture of prairie vegetation to four N fertilization rates across an 8-yr study. Among the species tested were western wheatgrass (Agropyron smithii Rydb.), blue grama (Bouteloua gracilis [H.B.H.] Lag.), threadleaf sedge (Carex filifolia, Nutt.), and needle-and-thread (Stipa comata Trin. & Rupr.). At N rates of 0, 45, 90, and 180 kg ha -1 forage DM production was 0.8, 1.9, 3.0, and 3.1 Mg ha -1 respectively. Nichols et al. (1990) also evaluated the response of smooth bromegrass (Bromus inermis Leyss.), redtop (Agrostis stolonifera L.), timothy (Phleum pratense L.), slender wheatgrass [Agropyron trachycaulum (Link) Malte], quackgrass [A. repens (L.) Beauv.], Kentucky bluegrass (Poa pratensis L.), prairie cordgrass (Spartina pectinata Link) and several sedges (Carex spp. L) and rushes (Juncus spp. L.) to N application over a 4-yr trial. Nitrogen was applied at rates of 0, 45, 90, and 135 kg ha -1 At these levels, forage DM production was 6.1, 6.9, 8.1, and 8.7 Mg ha -1 respectively. This study also reported the nutritive value response to increasing N rates. Across the treatments, there were no significant differences in either CP or IVDMD. Barley (Hordeum vulgare L.), a cool-season annual grass, can serve as an important alternative feed crop in the southeastern USA (DiRienzo et al., 1991). DiRienzo et al. (1991) evaluated barley yield responses to spring N applications across 2 yr. At N rates of 0, 45, 90, and 135 kg ha -1 forage DM yields were 9.6, 10.5, 11.0, and 11.5 Mg ha -1 respectively. Barley showed higher DM yields, however, response to N decreased as N

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11 rate increased having an initial response of 20 kg forage kg -1 N, but decreasing to 13 kg forage kg -1 N at the highest fertilization rate. Tropical Grasses Tropical C 4 grasses are used throughout the southern USA. Because of the growing environment, these grasses account for a large proportion of the nutrients in many ruminant animal diets in this region. These grasses also have the potential for response to N application. Bermudagrass is a C 4 grass used widely throughout the southeastern USA as a forage for livestock. Thom et al. (1990) evaluated Tifton 44 bermudagrass yield and nutritive value responses to N fertilization over a 5-yr period. At N rates of 0, 135, 270, 405, and 540 kg ha -1 forage DM yields were 2.5, 9.1, 15.8, 16.6, and 16.0 Mg ha -1 respectively. Bermudagrass DM yield responded up to the 405 kg ha -1 rate, but yield decreased at 540 kg ha -1 Looking at nutritive value, N application did not significantly increase the IVDMD of the bermudagrass; all treatments averaged approximately 600 g kg -1 Wiendenfeld (1988) evaluated Costal bermudagrass and Renner lovegrass [Eragrostis curvula (Schard.) Ness] response to N fertilization. In this study N was applied at 0, 112, and 224 kg ha -1 At these treatment levels, bermudagrass increased yield per unit N with increasing N rates. These responses suggest that bermudagrass could possibly have made efficient use of N above those applied in this study. In a study by Prine and Burton (1956), the effect of N rate was evaluated on yield and CP concentration of Coastal bermudagrass. At N levels of 0, 112, 336, 672, and 1008 kg ha -1 hay DM yields were 4.9, 7.5, 13.5, 17.2, and 18.4 Mg ha -1 respectively. Bermudagrass showed the highest increase in production (kg forage/kg N ha -1 ) at the 336 kg ha -1 rate and then showed a smaller response above this level. The forage CP concentrations were

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12 97, 113, 150, 170, and 190 g kg -1 Similar to yield, the greatest response to N was at 336 kg ha -1 and response leveled off at higher N rates. Limpograss [Hemarthria altissima (Poir) Stapf & C.E. Hubb] is another C 4 grass that serves an important role in the livestock industry in Florida. Limpograss is also known for its seasonally low N concentrations (Lima et al., 1999) and has the potential for a response to applied N. Christiansen et al. (1988) compared the response of three cultivars of limpograss to three N fertilization rates (0, 120, and 480 kg ha -1 ) and several defoliation intervals. At a defoliation interval of 3 wk, Floralta limpograss responded to these N rates with DM yields of 2.7, 4.4, and 6.8 Mg ha -1 respectively. Both CP and IVOMD increased in response to N rate and were 75, 90, and 97 g kg -1 and 499, 507, and 518 g kg -1 respectively. Lima et al. (1999) compared limpograss at N rates of 50 and 150 kg ha -1 Increasing the N rate resulted in an increase in carrying capacity of approximately 100 heifer days ha -1 in the year when rainfall was near normal, and carrying capacity was increased by 37 heifer days ha -1 in a drier than normal year (58% of the 70-yr average rainfall). Forage DM production increased to support the increase in carrying capacity. Increasing the N rate also increased CP and IVOMD of the blade, sheath, and stem portions of the plant. Velez-Santiago and Arroyo-Aguilu (1983) measured limpograss production and nutritive value at several fertilization rates. At rates of 224, 448, and 896 kg ha -1 DM production of Bigalta was 2.7, 3.5, and 4.4 Mg ha -1 respectively. At these N rates, CP concentrations also increased at a harvest interval of 30 d and were 94, 106, and 119 g kg -1 From these data it is apparent that limpograss has the potential to increase DM production and CP up to high levels of N application. Limpograss also shows an IVOMD response to N unlike many other tropical grasses.

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13 Other tropical grasses respond to N fertilization in terms of DM production and CP concentration. Fara et al. (1999) evaluated the nutritive value of Mott dwarf elephantgrass (Pennisetum purpureum Schum.) in response to N fertilization. At N rates of 0, 150, 300, and 450 kg ha -1 CP ranged from 80 to 83 g kg -1 and was not different among treatments. The IVDMD ranged from 600 to 620 g kg -1 ; these values were also not significantly different. Springer and Taliaferro (2001) evaluated N fertilization of buffalograss [Buchlo dactyloides (Nutt.) Engelm] across a range from 0 to 134 kg ha -1 At these levels, forage DM production significantly increased from approximately 1.8 to 2.7 Mg ha -1 The N rate also had a significant effect on CP, increasing it from 90 to 124 g kg -1 ; however, there was no significant effect on IVDMD. In a study by George et al. (1990), forage production and nutritive value of switchgrass (Panicum virgatum L.) were compared at two N levels, 0 and 90 kg ha -1 There was an increase in DM production from 1100 to 1800 kg ha -1 with N application. Also there was a significant increase in CP and IVDMD, with CP increasing from 120 to 160 g kg -1 and IVOMD from 670 to 700 g kg -1 respectively. Tyagi and Singh (1986) reported the effect of N application on forage production and nutritive value in dinanathgrass (Pennisetum pedicellatum Trin), a tropical grass native to Africa and India. In this study, N was applied at rates ranging from 0 to 160 kg ha -1 Forage DM productions increased from 9.1 to 20 Mg ha -1 with increasing N, but production did not increase above 120 kg ha -1 Forage CP significantly increased from 59 to 91 g kg -1 as N application increased from 0 to 160 kg ha -1 and digestibility increased from 606 to 658 g kg -1 over the same range of N rates.

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14 These data suggest that N fertilization increases grass production and CP concentration across a wide range of grass species and N rates. Nitrogen effects on other measures of forage nutritive value are less consistent. The next section of the review focuses on bahiagrass response to N fertilization. Bahiagrass Nitrogen is generally the most limiting nutrient for bahiagrass (Gates et al., 2004). In Floridas sandy soils, soil nutrient retention capacity is minimal due to their coarse texture and low organic matter concentration. Significant amounts of fertilizer are required in order for pastures to produce high production of forage and animal product. Blue (1988) conducted an experiment that evaluated Pensacola bahiagrass response to three rates of N application applied using five different schedules of application. He found that application date did not have a significant effect on total annual DM production; however, there was a large increase in production and forage N concentration with increasing N rate. Twidwell et al. (1998) reported that an increase in N rate from 0 to 445 kg ha -1 increased total DM production from 4.0 to 15.6 Mg ha -1 (3.9-fold yield increase). Burton et al. (1997) reported that increasing N rate from 56 to 448 kg ha -1 on Pensacola bahiagrass increased production from 6.0 to 15.1 Mg ha -1 Stanley (1994) applied N to Tifton 9 bahiagrass at rates of 0, 84, 168, 336, and 672 kg ha -1 In this study, he found DM productions of 7.4, 8.7, 10.9, 15.5, and 19.9 Mg ha -1 respectively. Forage production per unit N applied increased up to 336 kg ha -1 (24.1 kg forage/kg N ha -1 ), and decreased thereafter (18.6 kg forage/kg N ha -1 at 672 kg ha -1 ). Ruelke and Prine (1971) evaluated Pensacola bahiagrass along with seven other grasses at three fertility levels, 134, 269, and 538 kg N ha -1 Across 4 yr, the bahiagrass DM

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15 response to N was 6.7, 9.0, and 11.7 Mg ha -1 These data indicate that bahiagrass production can increase dramatically in response to increasing N fertilization. The potential for N fertilization to increase forage CP and change cell composition has been explored in previous studies. Twidwell et al. (1998) reported that an increase in N rate from 0 to 445 kg ha -1 increased total herbage CP from 105 to 144 g kg -1 respectively. Burton et al. (1997) reported that increasing N rate from 56 to 448 kg ha -1 on Pensacola bahiagrass increased forage N concentration from 11 to 17 g kg -1 Blue (1988) reported 2-yr average forage N concentrations of 35, 115, and 204 kg ha -1 for N applications of 0, 100, and 200 kg ha -1 respectively. Stanley et al. (1977) evaluated cell wall constituents across N rates of 0, 84, 168, and 336 kg ha -1 This study found no significant difference in cell wall composition across fertilization rates. From recent literature for bahiagrass, it is apparent that there is potential to increase production of bahiagrass in response to N fertilization. Also there is evidence of increased CP concentration as a result of N fertilization; however, the response of IVOMD is not consistent. Environmental Implications From the reviewed literature, it is evident that N fertilization increases grass yield and crude protein, and in turn, has the potential to increase animal production. However, increasing N rates will reach a point where there are diminishing returns to forage production and possibly significant N losses to the environment. The sandy, low organic matter soils in Florida have limited ability to retain N. Therefore, regulatory agencies are concerned with the potential of surface and ground water contamination from excessive N applications on agricultural land (Muchovej and Rechcigl, 1994). With increased stocking rates, there is also potential of increased nutrient loading from animal waste.

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16 Runoff and leaching of nutrients from animal waste may contaminated water supplies (Hammond, 1994). Proper management of animals and resources under increased management intensity is required to avoid these potentially harmful environmental impacts. Grazing Management Grazing management involves a series of choices that determine the nature of the plant-animal interaction on pasture. Primary choices include those of grazing method, grazing frequency, and grazing intensity. These will be discussed in the section that follows. Grazing Method Stocking method plays an important role in a grazing system. There are two general stocking methods utilized, rotational and continuous stocking. Rotational stocking consists of subdividing pastures into paddocks that have periods of both grazing and rest. This method generally allows for a higher stocking rate than continuous stocking (Blaser, 1986). In contrast, continuous stocking allows constant access to all areas of the pasture. At moderate stocking rates this method often results in greater gain per animal, associated with increased opportunity for diet selection, however, gain per unit land area may be less than with rotational stocking because of lower stocking rate (Blaser, 1986). Sollenberger et al. (1988) compared animal performance of Pensacola bahiagrass and Floralta limpograss on continuously stocked pastures. Pastures were fertilized at a N rate of 200 and 180 kg N ha -1 during a 2-yr study. A variable stocking rate was used and average stocking rates were 5.4 and 5.2 animals ha -1 for limpograss and bahiagrass, respectively (based on 320-kg animals). Cattle on bahiagrass had ADG of 0.38 kg d -1

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17 across the two grazing seasons, compared to 0.33 kg d -1 on limpograss. These authors pointed out that the lack of difference in ADG between forages might be associated with the low CP concentration of limpograss, even though limpograss IVOMD was higher than bahiagrass (539 and 484 g kg -1 respectively). Also in midto late summer, limpograss pastures had an accumulation of stem material that may have limited voluntary intake. Sollenberger et al. (1989) also compared animal performance on rotationally stocked Floralta limpograss and Pensacola bahiagrass pastures across three grazing seasons. The N rate for this study averaged 180 kg ha -1 yr -1 The ADG of animals grazing bahiagrass remained the same as that observed under continuous stocking and averaged 0.38. Cattle gains on limpograss were 0.41 kg d -1 and not different than those on bahiagrass. Average stocking rates of bahiagrass pastures under rotational stocking were 5.3 animals ha -1 compared to 6.7 animals ha -1 on limpograss. Williams and Hammond (1999) compared rotational and continuous intensive stocking of cattle on bahiagrass pastures. Cattle weight gains did not differ over the 3-yr trial. Forage IVOMD and CP were similar between rotational and continuous stocking. Hammond et al. (1997) also compared rotational stocking and continuous stocking as it affected animal performance of Angus cattle. This study found no difference in ADG among methods (0.68 kg d -1 for rotational and 0.67 kg d -1 for continuous). Mathews et al. (1994) compared Holstein heifer and Callie bermudagrass pasture response to rotational and continuous stocking over a 2-yr period. In this study, treatments were defined as rotational stocking (15 paddocks) with short grazing periods (1.5 to 2.5 d paddock -1 ) (RS-SG), rotational stocking (3 paddocks) with long grazing

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18 periods (10 to 14 d paddock -1 ) (RS-LG), and continuous stocking (CS). The study found no difference in season-long ADG for the rotational treatments in both years. During the first year, ADG on CS was significantly higher than either of the RS treatments; however there were no differences among treatments in the second year. Comparing average stocking rate among treatments showed that RS-SG was greater than RS-LG and CS during the first year (3920, 3200, and 3230 kg liveweight ha -1 d -1 respectively), and there were trends toward a similar response during the second year. The IVOMD values were not different across treatments during the first year; however, in the second year the RS-LG treatment was significantly higher than the CS, 574 and 558 g kg -1 respectively. There were no significant differences among CP values across treatments. The authors concluded that effect of grazing method on heifer performance was slight, but potential exists for long-term differences because Callie persistence was greater under rotational stocking. Tharel (1989) compared rotational and continuous stocking of three bermudagrass cultivars (Common, Tifton 44, and Midland). Both continuously and rotationally stocked pastures were 1 ha in size, and the rotational pastures were subdivided into 10, 0.1-ha paddocks. Average daily gains across cultivars were higher for continuous compared to rotational stocking, 0.7 and 0.6 kg d -1 respectively. On a gain per hectare basis, rotationally stocked pastures outperformed continuous, 730 and 600 kg ha -1 respectively. Grazing Frequency Data indicate a potential for increasing DM production with increasing intervals between grazing (decreasing grazing frequency; Mislevy and Brown (1991). Frequent removal of forage may decrease non-structural carbohydrate reserves, decreasing the plants ability to produce DM; however, as interval between grazings increases, CP and

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19 IVOMD decrease. Frequent grazing prevents plants from reaching maturity, thus increasing the proportion of young, lush herbage. Mislevy and Brown (1991) evaluated bahiagrass at four grazing frequencies, 2, 3, 5, and 7 wk across 3 yr. As interval between grazing increased, DM production increased from 7.1 to 10.8 Mg ha -1 yr -1 The grazing frequency effect on IVOMD was less in early season, but in mid-summer IVOMD decreased from 540 g kg -1 at 2 wk to 480 g kg -1 at 7 wk. The CP decreased with increasing interval between grazing in June (140 to 80 g kg -1 ) and in mid-summer (110 to 70 g kg -1 at 2 and 7 wk, respectively). Gates et al. (1999) evaluated bahiagrass at three cutting intervals, 2, 4, and 8 wk, during three growing seasons. With the exception of the 8-wk interval in Year 2, DM production increased as cutting interval increased. There was no change in IVDMD among cutting intervals, but there was a slight decreasing trend as interval increased. Cuomo et al. (1996) compared three grazing frequencies, 20, 30, and 40 d, of bahiagrass across two growing seasons. At these frequencies, total forage dry matter production was 10.6, 11.8, and 12.3 Mg ha -1 respectively. Herbage CP was significantly higher at the 20-d grazing frequency (124 g kg -1 ), but it was equal for the 30 and 40-d intervals (110 g kg -1 ). In vitro true digestibility did not significantly change across grazing frequencies. Beaty et al. (1970) evaluated bahiagrass across six harvest frequencies, 1, 2, 3, 4, 5, and 6 wk. At these frequencies, average DM productions for the 2 yr study were 3.5, 3.4, 3.0, 2.7, 3.8, and 2.6 Mg ha -1 respectively, showing little effect of clipping frequency. Stanley (1994) compared bahiagrass at harvest intervals of 1, 2, 4, 8, and 16 wk, with a N rate of 336 kg ha -1 Forage DM production was highest for the 8-wk interval (18.9 Mg ha -1 ). Relative production for the remaining harvest intervals (with DM productions of the 8-wk

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20 treatment assigned a value of 1.00) were 0.36, 0.53, 0.81, and 0.75 for the 1, 2, 4, and 16-wk treatments, respectively; illustrating an increase in forage production as harvest interval increases to 8-wk, but no further increase with delayed harvest. Adjei et al. (1989) compared bahiagrass, limpograss, and bermudagrass at four grazing frequencies (2, 4, 6, and 8 wk) for two growing seasons. At these grazing frequencies, Pensacola bahiagrass did not show a significant increase in DM production with longer intervals between grazing. Hemarthria 869 limpograss and Tifton 79 bermudagrass both showed a linear increase in DM production from the 2 to 8 wk interval, 1.8 to 5.6 Mg ha -1 and 4.3 to 7.8 Mg ha -1 respectively. There were linear and quadratic decreases in bahiagrass CP (130 to 73 g kg -1 ) as interval increased from 2 to 8 wk. Limpograss and bermudagrass CP also declined markedly with increasing interval, 107 to 57 g kg -1 and 160 to 65 g kg -1 respectively. Bahiagrass IVOMD decreased linearly with increasing interval between grazing (560 to 460 g kg -1 ). Limpograss did not show a significant change in IVOMD, but bermudagrass IVOMD decreased linearly from 610 to 470 g kg -1 This study also evaluated forage persistence at these grazing frequencies. Over all grass entries, there was a significant linear decrease in common bermudagrass invasion, from 51% to 36%, as interval between grazing increased. These data suggest that production responses of bahiagrass to defoliation frequency are likely smaller than those of more upright-growing grasses. This is probably due to the ability of bahiagrass to maintain leaf area even under frequent, close grazing and to self shading as regrowth interval increases. Grazing Intensity In a forage system, grazing intensity is an important means by which both animal and forage production can be manipulated. It is important to maximize forage utilization,

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21 but at the same time maintain a vigorous pasture stand. Grazing intensity can be characterized in a number of ways including grazing height and stocking rate. Stocking rate is defined as the relationship between the number or weight of animals and the area of pasture which is available for grazing over an extended period of time. Stocking rate has a major influence on forage production and animal performance, thus, it is considered to be the most significant grazing management decision (Matches, 1992). Increasing stocking rate increases the removal of available forage per unit land area; however, nutritive value or available forage may decrease as grazing height decreases. This reduction in quantity and or quality causes consumed energy to be reallocated from maximum daily animal growth to meeting the maintenance requirement (Burns et al., 2003), thus reducing production per animal. Conversely, increasing the stocking rate of an underutilized pasture causes an increase in animal production per unit land area up to a point (Mott and Lucas, 1952). Exceeding this point causes a decrease in production per unit land area due to the decline in forage availability and daily animal production; the latter occurs because a greater proportion of total forage intake is devoted to meeting the maintenance requirement of the animal. Consequently, stocking rate is an important factor influencing production of a given pasture. Adjei et al. (1980) evaluated pasture and animal response of three stargrass cultivars to three stocking rates (SR): 7.5, 10, and 15 cattle ha -1 (cattle = 250 kg avg. liveweight). Across 2 yr, forage DM production increased from 17.0 to 20.1 t ha -1 as SR increased from 7.5 to 15 cattle ha -1 For UF-5 stargrass, IVOMD and CP increased as SR increased (460, 488, and 523 g kg -1 and 87, 102, and 111 g kg -1 respectively). Average daily gain (ADG) of cattle on UF-5 decreased as stocking rate increased (0.46,

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22 0.37, and 0.24 kg d -1 ). Gain per unit land area increased from the 7.5 to 10.0 SR (570 to 610 kg ha -1 respectively), but decreased to 590 kg ha -1 as SR increased to 15 cattle ha -1 Conrad et al. (1981) compared performance of beef steers on two cultivars and three experimental hybrids of bermudagrass at four SR. Average SR across grasses were 4.6, 6.8, 8.8, and 9.0 head ha -1 With increasing SR, ADG decreased (0.83, 0.70, 0.48, and 0.38 kg head -1 d -1 respectively). Animal performance on a per unit land area basis increased from 581 to 738 kg ha -1 as SR increased from 4.6 to 6.8 head ha -1 but then decreased as SR increased to 8.8 and 9.0 head ha -1 (651 and 641 kg ha -1 respectively). Even though there are a lack of data related to stocking rate of bahiagrass pastures, from the data presented for other grasses, it appears likely that stocking rate will affect both forage and animal responses significantly. Summary Bahiagrass serves as an important feedstuff to the beef cattle industry in the Southeastern USA. Bahiagrass response to N fertilization is well documented in the literature, but the effects of grazing method and grazing intensity on pasture and animal responses have received less attention from researchers in the region. Research assessing the effects of management intensity, defined as combinations of N rate, stocking rate, and grazing method, on productivity of bahiagrass-livestock systems is thus deemed important for the future of these systems in Florida and the Southeast. The research that follows includes two experiments that address these issues.

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CHAPTER 3 HERBAGE AND ANIMAL PERFORMANCE RESPONSES TO MANAGEMENT INTENSITY OF CONTINUOUSLY STOCKED BAHIAGRASS PASTURES Introduction Pensacola bahiagrass (Paspalum notatum Flgge) is widely adapted in Florida and the Gulf Coast; however, it is lower in nutritive value and yield than many warm-season perennial grasses (Sollenberger, 2001). Consequently, performance per animal and per unit land area on bahiagrass pastures are often below levels typically observed for other planted C 4 grasses. Despite these limitations, bahiagrass tolerates close grazing and a wide range of soil conditions, and it is relatively easy to establish and resistant to weed encroachment. Due to these advantages, bahiagrass covers more area (1 million hectares) than any other planted grass in Florida (Chambliss, 2000). Approximately 80% of all planted grasslands in Florida are seeded to bahiagrass, and more than 90% of bahiagrass pastures are used for grazing by beef cattle. Over the past 40 yr, the population of Florida has grown from approximately five million to 16 million and is projected to reach 24 million by the year 2030 (Arndorfer, 2003). Given this scenario, it is likely that land area available for agricultural uses will decrease further, and producers may face the task of maintaining economic livelihood on less land. A possible solution to this problem is to increase management intensity to achieve equal or higher gains on smaller amounts of land. Management intensity within the context of bahiagrass-based grassland systems includes N fertilizer rate, animal stocking rate, and grazing management. Currently there is little information in the 23

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24 literature regarding the effect of increasing N fertilizer rate and stocking rate on performance of animals grazing bahiagrass pasture. Nitrogen is generally the most limiting nutrient for bahiagrass swards (Gates et al., 2004), and N fertilization has the potential to increase both herbage accumulation and crude protein (CP) concentration (Blue, 1988; Burton et al., 1997; Twidwell et al., 1998). With increased herbage accumulation, stocking rate can be increased to utilize the additional herbage while potentially maintaining the same rate of daily live weight gain. Should this occur, the result would be an increase in gain per unit land area on N fertilized bahiagrass pastures. Therefore research was conducted to evaluate the effect of a range of management intensities of continuously stocked bahiagrass pastures on performance of yearling beef heifers. Treatments were chosen to encompass and exceed the range in management intensity used by current producers. The specific objectives of this study were to evaluate the effects of combinations of N fertilizer rate and stocking rate of bahiagrass pastures on herbage mass, accumulation, and nutritive value, and yearling beef heifer daily gain and gain per hectare. Methods and Materials Experimental Site This experiment was conducted at the Beef Research Unit, located northeast of Gainesville, FL (29 43' N lat.). Pastures used were well-established swards of Pensacola bahiagrass that had been stocked rotationally at similar stocking rates (1.5 animal units [AU, one AU=500 kg live weight] ha -1 ) during the previous five summer grazing seasons. Soils at the site were predominantly of the Pomona and Smyrna series of sandy Spodisols

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25 with average pH of 5.9. Soil P, K, Ca, and Mg concentrations were 5.3, 28, 553, and 98 mg kg -1 respectively. Treatments and Design For the purposes of this experiment, management intensity was defined as a combination of a N fertilizer rate and an animal stocking rate. The three management intensity treatments were LOW (40 kg N ha -1 yr -1 1.2 AU ha -1 stocking rate), MODERATE (120 kg N ha -1 yr -1 2.4 AU ha -1 stocking rate), and HIGH (360 kg N ha -1 yr -1 3.6 AU ha -1 stocking rate), and treatments were arranged in two replicates of a randomized block design. Pasture sizes were varied to achieve the treatment stocking rates and were 1, 0.5, and 0.33 ha for the LOW, MODERATE, and HIGH treatments, respectively. The target stocking rates were chosen based on the projection that heifers with an average initial weight of 270 to 275 kg would be assigned to all treatments and would gain 0.35 kg d -1 (based on Sollenberger et al., 1989) over a 160-d trial to achieve a final weight of 325 to 330 kg. This would result in an average weight of approximately 300 kg during the grazing season and an average stocking rate appropriate for that treatment. Because heifer live weights were greater than expected at the start of grazing each year, actual SR was greater than our target and is reported in Table 3-1. The range of treatments was selected to bound those used by most beef cow-calf producers in Florida. The LOW treatment approximates the current industry average, while MODERATE represents the most intensive of current management practices. The HIGH treatment represents a considerable increase in management intensity from any current management, but one that is within reason should land limitations to cattle production become severe. The choices of N rate and stocking rate for HIGH were based on data from Burton (1997) and Twidwell et al. (1998) who found that bahiagrass forage

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26 production was approximately three times greater for N rates near the highest compared to the lowest used in the current study, thus keeping forage mass and stocking rate nearly in balance across these treatments. Table 3-1. List of actual stocking rates (SR) of continuously stocked bahiagrass pastures. Actual SR (AU ha -1 ) Target SR (AU ha -1 ) 2001 2002 1.2 1.5 1.4 2.4 3.0 2.8 3.6 4.4 4.1 AU = 500 kg live weight Pasture and Animal Management Bahiagrass pastures were continuously stocked during the growing seasons of 2001 (112 d) and 2002 (168 d). Grazing was initiated in the spring or early summer of each year when adequate forage was available to support the livestock (26 June 2001 and 22 May 2002). Grazing was delayed in 2001 because of April and May drought (Table 3-2). The LOW and MODERATE treatment pastures received 40 kg N ha -1 when temperature and soil moisture conditions favored a response to N (June 2001 and April 2002). It is typical for all N to be applied to grazed bahiagrass during spring by Florida beef producers because forage is in short supply and the breeding season is underway. The MODERATE pastures received two additional applications of 40 kg N ha -1 one in mid-July, and the other in mid-August. The HIGH pastures received four applications of 90 kg N ha -1 in 2002, in late April/early May, mid-June, mid-July, and mid-August.

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27 Because the grazing season was shorter than normal in 2001, the HIGH treatment only received 270 instead of 360 kg N ha -1 yr -1 Actual N fertilization dates for both years are reported in Table 3-3. Phosphorus (17 kg ha -1 ) and K (66 kg ha -1 ) were applied to all treatments prior to N application in 2001 (17 April) and at the first N application in 2002 (30 April). MODERATE and HIGH treatments received a second application of the same rates on 15 July 2002. Table 3-2. Rainfall at the experiment site for years 2001-2002 and the 30-yr average for Gainesville, FL. Rainfall (mm) 2001 2002 Month 30-yr Average Actual Departure From normal Actual Departure From normal Jan 83 12 -71 99 15 Feb 99 25 -74 25 -74 Mar 93 164 71 50 -43 Apr 75 28 -47 62 -12 May 106 22 -85 33 -73 June 168 176 8 135 -34 July 180 248 68 249 69 Aug 203 71 -132 165 -38 Sept 142 183 40 133 -10 Oct 59 9 -50 63 4 Nov 52 20 -31 95 43 Dec 81 50 -31 128 47 Two crossbred (Angus X Brahman) yearling beef heifers of average 344 and 313 kg liveweight were assigned to each pasture in 2001 and 2002, respectively. No other animals were added to the pasture throughout the course of the grazing season. Cattle

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28 were provided free-choice access to water and a trace mineral mix (Table 3-4). Artificial shade (3.1 x 3.1 m) was available on all treatments. Table 3-3. Nitrogen application dates on continuously stocked bahiagrass pastures. N application dates (rates in kg ha -1 ) Treatment 2001 2002 Low 13 June (40) 30 Apr (40) Moderate 13 June (40) 30 Apr (40) 20 July (40) 15 July (40) 24 Aug (40) 20 Aug (40) High 13 June (90) 30 Apr (40) 20 July (90) 14 May (50) 24 Aug (90) 12 June (90) 15 July (90) 20 Aug (90) Table 3-4. Composition of mineral supplement. Mineral g kg -1 Ca 200 230 P 60 Na 230 250 Fe 10 F 0.6 Co 0.0005 Cu 0.005 I 0.0005 Mn 0.02 Se 0.00012 Zn 0.04

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29 Pasture Responses Pastures were sampled just prior to initiation of grazing and every 14 d thereafter during the grazing season. Herbage mass, herbage accumulation, and herbage nutritive value (CP and in vitro digestibility) were measured. Double sampling was used to determine herbage mass. Double sampling refers to a technique that includes both a direct and indirect measure of the response of interest. In this case the indirect measure was settling height of a 0.25-m 2 aluminum disk, and the direct measure was hand clipping of all herbage from 2 cm above soil level to the top of the canopy. At each sampling date, 30 disk heights were taken in each pasture. Sites were chosen by walking a fixed number of steps between drops of the disk and all sections of the pasture were represented. Every 28 d, 20 double samples were taken, approximately three to four in each of the six experimental pastures. Sites were chosen that represented the range of herbage mass present on the pastures. At each site the disk height was measured and the forage clipped. Clipped forage was dried for 48 h and weighed. Actual herbage mass was regressed on disk height to develop a calibration equation. This equation from the double samples was used to predict pasture herbage mass using the average disk height (from the 30 disk heights) for each pasture. Regression equations are presented in Table 3-5. Because cattle were resident on these pastures at all times, a cage technique was used to measure herbage accumulation. Six 1-m 2 cages were used per pasture. The cages were placed in the pasture at the initial sampling date. Sites were chosen that had a disk settling height that was approximately the same (cm) as that of the average on that pasture. Disk settling height was recorded at a specific site and the cage placed. After 14 d, the cage was removed and the new disk settling height recorded. Herbage accumulation was calculated as the change in herbage mass during the 14 d that the cage

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30 was present. At the end of each 14-d period, cages were moved to new locations on the pasture that approximated the average disk settling height for the pasture. Table 3-5. Herbage mass double sample regression equations. 2001 2002 Date Equation R 2 Date Equation R 2 11 July y = 220 97 0.82 22 May y = 235x 313 0.86 8 Aug. y = 251x 250 0.84 19 June y = 260x 331 0.75 4 Sept. y = 337x 401 0.85 14 July y = 336x 724 0.78 2 Oct. y = 279x + 359 0.80 14 Aug. y = 328x 648 0.83 11 Sept. y = 299x 277 0.81 9 Oct. y = 357x 447 0.82 Forage allowance is defined as herbage mass per unit of animal liveweight. Forage allowance was calculated for each pasture during each 28-d period as the average herbage mass (mean across three sampling dates in that 28-d period) divided by the average total liveweight during that period. Herbage CP and in vitro organic matter digestibility (IVOMD) were used as measures of nutritive value. At initiation of grazing and every 14 d thereafter, hand-plucked samples were taken from each pasture. This technique attempts to represent the diet consumed by the grazing animal by removing only the top 5 cm of herbage at approximately 30 locations across each pasture. The herbage was dried at 60C and ground to pass a 1-mm screen. Analyses were conducted at the Forage Evaluation

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31 Support Laboratory using the micro-Kjeldahl technique for N (Gallaher et al., 1975) and the two-stage technique for IVOMD (Moore and Mott, 1974). Bahiagrass cover was estimated visually at the beginning of the 2001 grazing season and the end of the 2002 grazing season. Five equally spaced line transects were established for each paddock. Percent bahiagrass was estimated at eight locations along each transect for a total of 40 observations per paddock. Data reported are changes in bahiagrass cover between those two dates. When pasture data are reported as total-season averages, the data are the averages of all of the 14-d sampling interval data across the season. When reported as 28-d period averages, the data are the average of the three sampling dates within each 28-d period (Days 0, 14, and 28). Animal Responses Cattle were weighed at initiation of the experiment and every 28 d thereafter. Weights were taken at 0800 h following a 16-h feed and water fast. Average daily gain was calculated for each 28-d period and for the entire grazing season. Weight gain per hectare was calculated for each pasture over the entire grazing season. Statistical Analysis Data representing annual totals or averages (e.g., total herbage accumulation, average pasture herbage mass, average herbage accumulation rate, average herbage allowance, average CP and IVOMD, and average daily gain, gain per hectare) were analyzed using analysis of variance in PROC GLM of SAS (SAS Institute Inc., 1996) with treatment as the main plot and year the subplot. Data representing time trends throughout the season (measured every 14 or 28 d and including herbage accumulation rate, herbage mass, herbage allowance, average daily gain by period, CP, IVOMD) were

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32 analyzed using repeated measures analysis of variance in PROC GLM of SAS (SAS Institute Inc., 1996) with treatment as a fixed effect and sampling date as the repeated variable. In addition to analysis of variance to determine treatment effects on forage allowance, regression analysis was conducted using PROC REG of SAS (SAS Institute Inc., 1996) to assess the relationship between forage allowance and heifer average daily gain. Results and Discussion The average maximum temperature for both experimental periods of 2001 and 2002 was 31C, and the average minimum temperature was 19C (Table 3-6). Total annual rainfall was 1008 and 1236 mm for 2001 and 2002, respectively (30-yr average of 1342 mm; Table 3-2). Rainfall during the experimental period was 540 mm in 2001 and 751 mm in 2002. Table 3-6. Monthly average temperatures at the experiment site for years 2001-2002. Temperature (C) 2001 2002 Month Min Max Min Max Jan 18.8 1.3 19.7 5.2 Feb 24.4 9.3 20.7 5.3 Mar 22.2 9.2 25.5 8.9 Apr 27.4 10.5 29.4 16.0 May 30.4 15.0 30.8 15.6 June 32.3 20.3 31.2 20.4 July 32.2 22.1 32.3 21.3 Aug 32.7 21.6 31.4 21.0 Sept 29.9 19.1 31.4 21.7 Oct 26.8 12.7 28.9 17.7 Nov 25.0 10.8 22.7 8.1 Dec 23.1 9.2 19.6 4.5

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33 Herbage Mass There was a trend toward a year effect (P=0.06) on average herbage mass, with mass tending to be greater in 2001. This trend can be explained in part due to starting sooner in 2002 and the experimental period including late spring/early summer. Herbage mass values were lower and caused the seasonal average to be lower than in 2001. There was no year X management intensity interaction for herbage mass (P=0.79; Table 3-7). Across years, herbage mass was greater for the LOW treatment than for MODERATE or HIGH. Bahiagrass herbage accumulation generally increases with increasing N rate (Beaty et al., 1977; Burton, 1997; Blue, 1988), but in this experiment, the increase in stocking rate associated with greater N rates apparently more than compensated for the greater pasture growth rates in MODERATE and HIGH and resulted in lower herbage mass. The three treatments all followed a similar seasonal pattern in herbage mass (Figures 3-1 and 3-2). Herbage mass was relatively low (1.5-2.8 Mg ha -1 ) early in the grazing season, increased to a maximum, and decreased late in the season in both years. Previous research has shown a similar pattern of herbage mass in bahiagrass pastures, peaking in mid-summer (July August) under typical rainfall conditions (Sumner et al., 1991; Johnson et al., 2001). There were no intensity effects on herbage mass during any 28-d weighing periods through the 2001 grazing season (P=0.19, P=0.20, P=0.26, and P=0.87); however, there was a trend for the LOW treatment to have higher average herbage mass in the first three periods. There was a management intensity X period interaction for herbage during 2002. This occurred because herbage mass for the HIGH treatment was significantly higher

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34 Table 3-7. Pasture herbage mass (HM) and herbage accumulation rate (HAR) responses to management intensity of continuously stocked bahiagrass pastures. HM HAR Treatment 2001 2002 AVG 2001 2002 AVG -----------------Mg ha -1 -------------------------------kg ha -1 d -1 ---------Low 3.18 2.77 2.98 a 23.7 15.2 19.4 b Moderate 2.76 2.31 2.54 b 21.3 44.5 32.9 a High 2.69 2.44 2.56 b 30.3 43.7 37.0 a LSD (0.05) 0.04 7.4 S.E. 0.007 1.22 There was no treatment X year interaction for HM (P=0.79) or HAR (P=0.20). Treatments = Low (1.2 animal units [AU] ha -1 and 40 kg N ha -1 ); Moderate (2.4 AU ha -1 and 120 kg N ha -1 ); High (3.6 AU ha -1 and 360 kg N ha -1 ). Means within a column followed by the same letter are not significantly different at the 0.05 probability level. than for LOW at the first two dates (Fig. 3-2), but by the last observation of the season, HIGH herbage mass was significantly lower than for the LOW treatment (2.1 and 3.2 Mg ha -1 ). Higher herbage mass early in the season on HIGH was likely due to a greater N rate, but that advantage disappeared over time due to greater stocking rate than on LOW. During mid-summer of the 2002 grazing season, there were no differences among treatments (P=0.11, P=0.18, and P=0.16) but the trends favored the LOW treatment. Herbage Accumulation Rate There was no year or year X management intensity effect on average herbage accumulation rate (P=0.19 and P=0.20), but there was an effect of management intensity (P0.02). This was a result of the MODERATE and HIGH treatments having greater

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1.522.533.5427-Jun11-Jul25-Jul8-Aug22-Aug5-Sep19-Sep3-Oct17-OctDateHM (kg ha-1) Low Mod High 35 Figure 3-1. Herbage mass (HM) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11 July (P=0.19), 8 August (P=0.20), 5 September (P=0.26), and 3 October (P=0.87). Standard errors for means on 11 July, 8 August, 5 September, and 3 October are 0.13, 0.17, 0.16, and 0.28, respectively.

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1.01.52.02.53.03.54.04.58-May22-May5-Jun19-Jun3-Jul17-Jul31-Jul14-Aug28-Aug11-Sep25-Sep9-Oct23-OctDateHM (kg ha-1) Low Mod High aaaababbbbb 36 Figure 3-2. Herbage mass (HM) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 17 July (P=0.11), 14 August (P=0.18), and 11 September (P=0.16). Means within other dates bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 0.06, 0.11, 0.14, 0.19, 0.26, and 0.16, respectively.

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37 herbage accumulation rate than the LOW treatment (Table 3-7). Previous research (Ruelke and Prine, 1971; and Stanley, 1994) has shown bahiagrass herbage accumulation increasing dramatically as a result of increased N fertilization. Previous studies of other tropical grasses also show increasing herbage mass as a result of higher growth rates under greater N application (Thom et al., 1990; Wiendenfeld, 1988). In the current study herbage accumulation rate was greater for HIGH and MODERATE than LOW despite LOW having greater average herbage mass. HIGH and MODERATE received more N to increase herbage accumulation; however, the grazing pressure from the increasing SR of these treatments removed the herbage at a faster rate, causing herbage mass to decrease. During the 2001 grazing season (26 June to 16 October), there were no differences in herbage accumulation rate among treatments during any 28-d period (Figure 3-3); however, there were trends (P0.21) favoring HIGH during three of the four periods. The LOW and HIGH treatments followed similar patterns with decreasing herbage accumulation from the beginning of grazing to late summer, and then slightly increasing in early fall. The MODERATE treatment increased slightly from grazing initiation to mid-summer, then decreased in late summer, and leveled off during early fall. During the 2002 grazing season (8 May to 23 October) there were no differences in herbage accumulation rate among treatments during any 28-d period (Figure 3-4). All treatments followed a similar trend through the grazing season, with low accumulation rates in spring, increasing to a maximum during mid-summer, and then decreasing in late summer/early fall. This response is similar to the herbage mass seasonal trend in 2001, and can be explained in part by the change in temperature and rainfall at the beginning

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01020304050607027-Jun11-Jul25-Jul8-Aug22-Aug5-Sep19-Sep3-Oct17-OctDateHAR (kg ha-1 d-1) Low Mod High 38 Figure 3-3. Herbage accumulation rate (HAR) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11 July (P=0.14), 8 August (P=0.93), 5 September (P=0.21) and 3 October (P=0.15). Standard errors for means on 11 July, 8 August, 5 September, and 3 October are 4.5, 14.8, 19.4, and 2.5, respectively.

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-200204060801001208-May22-May5-Jun19-Jun3-Jul17-Jul31-Jul14-Aug28-Aug11-Sep25-Sep9-Oct23-OctDateHAR (kg ha-1 d-1) Low Mod High 39 Figure 3-4. Herbage accumulation rate (HAR) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 22 May (P=0.59), 19 June (P=0.35), 17 July (P=0.16), 14 August (P=0.12), 11 September (P=0.33), and 9 October (P=0.13). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 12.6, 6.5, 11.6, 12.8, 11.7 and 8.6, respectively.

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40 and end of the growing season. The decline in growth rate experienced in midto late summer, however, is more likely a response to decreasing daylength (Sinclair et al., 2003). In both grazing seasons, herbage accumulation rate reached its maximum in mid-July and then decreased throughout the remainder of the season. This is a typical growth pattern for C 4 grasses in this environment (Sumner et al., 1991). Crude Protein There was no year effect (P=0.19) on average herbage CP, nor was there a year X management intensity treatment interaction (P=0.56). There was an effect (P0.05) of management intensity on herbage CP. This effect was reflected in the general increase in CP as management intensity increased (Table 3-8). Increasing CP with greater N rates is commonly reported for bahiagrass and other tropical grasses (Velez-Santiago and Arroyo-Aguilu, 1983; Christiansen et al., 1988; Burton et al., 1997; Twidwell et al., 1998). The response of bahiagrass forage CP to increased levels of N is not as large as other tropical grasses, but the increase in bahiagrass stolon-root N is greater (Blue et al., 1980). The reported increase in forage N harvested was 68 kg ha -1 as N increased from 0 to 336 kg ha -1 compared to 104 for Ona stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis). The increase in bahiagrass stolon-root N was 86 kg ha -1 compared to an actual decrease of 3 kg ha -1 in stargrass. Therefore, even though bahiagrass herbage may not show as great an increase in N, it is still utilized, but stored in the stolons. During the 2001 grazing season (11 July to 3 October), there were no differences in CP among treatments during the first 28-d period (P=0.22), but there were differences among treatments at the remaining periods. The HIGH treatment had greater CP than both MODERATE and LOW, and MODERATE was greater than LOW (Figure 3-5).

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41 All treatments followed a similar seasonal trend, decreasing from midto late-summer, and then remaining relatively constant for the remainder of the grazing season. Table 3-8. Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD) responses to management intensity of continuously stocked bahiagrass pastures. CP IVOMD Treatment 2001 2002 AVG 2001 2002 AVG ------------------g kg -1 ----------------------------------g kg -1 -------------Low 92 102 97 b 426 478 452 b Moderate 111 111 111 b 445 496 471 b High 133 143 138 a 453 536 495 a Average 441 b 503 a LSD (0.05) 15 23 S.E. 2.5 3.78 There was no treatment X year interaction for CP (P=0.56) or IVOMD (P=0.57). Treatments = Low (1.2 animal units [AU] ha -1 and 40 kg N ha -1 ); Moderate (2.4 AU ha -1 and 120 kg N ha -1 ); High (3.6 AU ha -1 and 360 kg N ha -1 ). Means within a column followed by the same letter are not significantly different at the 0.05 probability level. There was a year effect on IVOMD (P=0.02). During the 2002 grazing season (22 May to 9 October), there were no differences among treatments on 17 July (P=0.17), but before and thereafter there were differences among treatments for all dates. Herbage CP for HIGH was greater than for both MODERATE and LOW throughout the grazing season (Figure 3-6). All treatments followed a similar seasonal pattern. Herbage CP increased to mid-summer, decreased slightly to late summer, and then remained relatively constant level for the remainder of the season.

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40608010012014016027-Jun11-Jul25-Jul8-Aug22-Aug5-Sep19-Sep3-Oct17-OctDate CP (g kg-1) Low Mod High cbacbacba 42 Figure 3-5. Herbage crude protein (CP) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11 July (P=0.22). Means within other dates bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 11 July, 8 August, 5 September, and 3 October are 7.8, 2.9, 2.3, and 1.7, respectively.

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801001201401601808-May22-May5-Jun19-Jun3-Jul17-Jul31-Jul14-Aug28-Aug11-Sep25-Sep9-Oct23-OctDateCP (g kg-1) Low Mod High bbbbcbbabbbaaaaa 43 Figure 3-6. Herbage crude protein (CP) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 17 July (P=0.17). Means within other dates bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 2.6, 5.2, 9.8, 3.4, 4.5 and 5.1, respectively.

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44 In Vitro Organic Matter Digestibility There was a year effect on average herbage IVOMD (P=0.02). This can be attributed in part to the inclusion of the late spring/early summer portion of the grazing season in 2002, a time generally characterized by higher forage digestibility (Blaser, 1986). There was no year X management intensity interaction (P=0.57), but there was a management intensity effect across years (P=0.03). The HIGH treatment had greater IVOMD than either the LOW or MODERATE treatments (Table 3-8). Increasing N application often has little or no effect on IVOMD of bahiagrass and other tropical grasses (Adjei et al., 1980; Thom et al., 1990). In the current experiment, the greater IVOMD for the HIGH treatment is most likely due to the increase in stocking rate. Higher stocking rate likely decreased the time period between animal visits to a given site in the pasture. This resulted in more frequent removal of grass, causing it to be less mature on average, thus having greater digestibility (Mislevy and Brown, 1991; Hernandez Garay et al., in review). During the 2001 grazing season there were no differences in herbage IVOMD among treatments during the first three sampling periods, however, during the last observation period of the season, IVOMD of HIGH was greater than that of LOW (Figure 3-7). During the 2002 grazing season (22 May to 9 October), there were no differences among treatments for the 17 July, 11 September, and 9 October periods, however for the remaining periods there was an effect of management intensity on IVOMD. Herbage IVOMD on HIGH was greater than on LOW on 22 May and 14 August and greater than both LOW and MODERATE on 19 June (Figure 3-8). Generally, the treatments followed similar patterns each year, with IVOMD decreasing

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30035040045050055060027-Jun11-Jul25-Jul8-Aug22-Aug5-Sep19-Sep3-Oct17-OctDateIVOMD (g kg-1) Low Mod High abab 45 Figure 3-7. Herbage in vitro organic matter digestibility (IVOMD) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11 July (P=0.22), 8 Aug (P=0.67), and 5 September (P=0.21). Means within a date bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 11 July, 8 August, 5 September, and 3 October are 7.1, 10.7, 11.5, and 6, respectively.

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3003504004505005506008-May22-May5-Jun19-Jun3-Jul17-Jul31-Jul14-Aug28-Aug11-Sep25-Sep9-Oct23-OctDateIVOMD (g kg-1) Low Mod High aaaabbbbab 46 Figure 3-8. Herbage in vitro organic matter digestibility (IVOMD) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 17 July (P=0.32), 11 September (P=0.59), and 9 October (P=0.11). Means within a date bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 7.1, 2.2, 11.6, 2.8, 20.6 and 17.3, respectively.

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47 slowly through the season. This decrease can partly be explained by high temperatures and increased rain through mid-summer (Jones, 1985; Wilson, 1983). An exception was the HIGH treatment in 2002 which increased slightly during late summer/early fall. On this heavily stocked treatment, the IVOMD likely responded this way because of decreasing herbage mass (Fig. 3-2) and more and more frequent visits by cattle to grazing stations in the pasture. Herbage Allowance There was no year effect (P=0.79) or year X management intensity interaction (P=0.55) on herbage allowance. There was an effect (P0.05) of management intensity on herbage allowance, and allowance decreased as management intensity increased above the LOW treatment (Table 3-9). This was a result of lower herbage mass and increasing stocking rate. Increasing stocking rate increases the removal of available forage per unit land area (Burns et al., 2003), resulting in decreasing herbage mass and allowance (Hernandez Garay et al., in review). Seasonal herbage allowance followed similar trends in both 2001 and 2002. Allowance increased to a maximum in midto late summer and then decreased in early fall. There were differences among treatments during all periods of the 2001 grazing season. Allowance on the LOW treatment was greater than on HIGH during midto late summer (8 August and 5 September), and greater than both HIGH and MODERATE at the beginning and end of the season (11 July and 3 October) (Figure 3-9). During the 2002 grazing season, there were no differences among treatments on 22 May (P=0.39) and 19 June (P=0.43), but as the season progressed, the LOW treatment had a greater allowance than MODERATE and HIGH on 17 July. For the remainder of the season there were differences among all treatments, with LOW having the highest allowance,

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0.01.02.03.04.05.027-Jun11-Jul25-Jul8-Aug22-Aug5-Sep19-Sep3-Oct17-OctDateHA (kg forage kg-1 an wt) Low Mod High bbbbbabbaaaaab 48 Figure 3-9. Herbage allowance (HA) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001. Dates are the midpoint of 28-d weighing periods. Means within a date bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 11 July, 8 August, 5 September, and 3 October are 0.37, 0.53, 0.61, and 0.20, respectively.

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49 followed by MODERATE and then HIGH (Figure 3-10). These trends can be explained by the seasonal changes of herbage mass. As HM increases during mid-summer, allowance increases and as HM decrease later in the season so does allowance. The changes in herbage allowance are reflected in the seasonal changes in ADG, which will be discussed later. Table 3-9. Herbage allowance response to management intensity. Treatment 2001 2002 AVG --------kg forage kg -1 an. wt.------Low 4.10 3.93 4.01 a Moderate 1.83 1.65 1.74 b High 0.96 1.19 1.07 b LSD (0.05) 1.77 S.E. 0.29 Treatments = Low (1.2 animal units [AU] ha -1 and 40 kg N ha -1 ); Moderate (2.4 AU ha -1 and 120 kg N ha -1 ); High (3.6 AU ha -1 and 360 kg N ha -1 ) Means within a column followed by the same letter are not significantly different at the 0.05 probability level. There was no treatment X year interaction for CP (P=0.55). Average Daily Gain There was no year effect (P=0.12) on average daily gain (ADG) nor was there a year X management intensity interaction (P=0.65). There was an effect of management intensity on ADG (P 0.01). Across years, ADG decreased as management intensity increased (Table 3-10). This did not occur because of changes in herbage nutritive value, because it was greater for HIGH than LOW. Instead it appears to be related to quantity of herbage, and both herbage mass and herbage allowance decreased with increased

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01234568-May22-May5-Jun19-Jun3-Jul17-Jul31-Jul14-Aug28-Aug11-Sep25-Sep9-Oct23-OctDateHA (kg forage kg-1 an wt) Low Mod High aaaabbbbcccab 50 Figure 3-10. Herbage allowance (HA) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 22 May (P=0.39), and 19 June (P=0.43). Means within other dates bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 0.39, 0.43, 0.45, 0.08, 0.08 and 0.06, respectively.

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51 management intensity. Therefore, even though the herbage present was higher in nutritive value, there was not enough herbage to support increased gains as management intensity increased. Similar responses were observed for stargrass in Jamaica (Hernandez Garay et al., in review) and for bermudagrass [Cynodon dactylon (L.) Pers.] in Texas (Conrad et al., 1981). Table 3-10. Heifer average daily gain (ADG) and gain per hectare (GPH) responses to management intensity. ADG GPH Treatment 2001 2002 AVG 2001 2002 AVG ------------------kg d -1 ------------------------------kg ha -1 ---------------Low 0.49 0.42 0.46 a 109 143 126 b Moderate 0.50 0.38 0.44 b 225 253 239 a High 0.38 0.34 0.36 c 257 342 299 a LSD (0.05) 0.01 S.E. 0.002 10 There was no treatment X year interaction for ADG (P=0.65) or GPH (P=0.70). Treatments = Low (1.2 animal units [AU] ha -1 and 40 kg N ha -1 ); Moderate (2.4 AU ha -1 and 120 kg N ha -1 ); High (3.6 AU ha -1 and 360 kg N ha -1 ). Means within a column followed by the same letter are not significantly different at the 0.05 probability level. During the 2001 grazing season there were no differences in cumulative ADG among treatments for the 11 July (P=0.10), 8 August (P=0.67), and 3 October (P=0.21) periods. For the 5 September period, ADG for the LOW treatment was greater than for the HIGH treatment (Figure 3-11). During the grazing season, ADG on the LOW treatment decreased to mid-summer, increased to late summer, and then decreased

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0.200.300.400.500.6027-Jun11-Jul25-Jul8-Aug22-Aug5-Sep19-Sep3-Oct17-OctDateADG (kg d-1) Low Mod High abab 52 Figure 3-11. Yearling beef heifer cumulative average daily gain (ADG) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2001. There were no differences among treatments on 25 July (P=0.10), 22 August (P=0.81), and 17 October (P=0.22). Means on 19 September bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 8 July, 7 August, 6 September, and 1 October are 0.05, 0.06, 0.03, and 0.04, respectively.

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53 slightly to early fall. The MODERATE treatment had a steep increase to mid summer and then increased slightly through the remainder of the season. The HIGH treatment increased to mid-summer, decreased to late summer, and increased slightly to early fall. During the 2002 grazing season (22 May to 9 October), there were no differences in cumulative ADG among treatments for the 19 June (P=0.35), 14 August (P=0.14), 11 September (P=0.21), and 9 October (P=0.45) periods. On 22 May and 17 July, ADG on the LOW treatment was greater than the HIGH treatment (Figure 3-12). During the grazing season, all treatments followed a similar trend, decreasing after the first observation, then increasing and leveling off in mid-summer, and decreasing to late summer/early fall. Herbage allowance incorporates both pasture and animal aspects, therefore it can be useful in explaining animal responses in trials with wide ranges of pasture herbage mass (Hernandez Garay et al., unpublished data). These authors report a strong relationship between increasing herbage allowance and ADG. During the 2001 season in the current study there was no relationship between ADG and herbage mass (P=0.99). There was a trend towards both a linear and quadratic relationship between ADG and herbage allowance (P=0.12 and P=0.14). During 2002 there was no relationship between ADG and herbage mass (P 0.81) or ADG and herbage allowance (P0.48). Gain per Hectare There was no year effect (P=0.19) on gain per hectare, nor was there a year X management intensity interaction (P=0.70). There was an effect of management intensity (P0.05). Gain per hectare increased as management intensity increased from LOW to MODERATE (Table 3-10) and was not different between MODERATE and HIGH. Understocked pastures accumulate forage that becomes both underutilized and overly

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0.100.200.300.400.500.600.700.800.901.008-May22-May5-Jun19-Jun3-Jul17-Jul31-Jul14-Aug28-Aug11-Sep25-Sep9-Oct23-OctDateADG (kg d-1) Low Mod Highaaababbb 54 Figure 3-12. Yearling beef heifer cumulative average daily gain (ADG) response to three levels of management intensity on continuously stocked bahiagrass pastures in 2002. There were no differences among treatments on 19 June (P=0.35), 14 August (P=0.14), 11 September (P=0.21), and 9 October (P=0.45). Means within other dates bordered by the same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 0.05, 0.10, 0.01, 0.02, 0.03, and 0.04, respectively.

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55 mature. Increasing SR increases forage utilization thus increasing animal production on a per unit land area basis (Mott and Lucas, 1952). Conrad et al. (1981) reported similar results on bermudagrass, however they noted that an increase in production per unit land area can only increase to a certain extent, and then the forage genetics become the limiting factor. On similar tropical forages, intake per animal decreases with increasing SR; however, higher percentages of the seasonal DM yield are utilized per unit land area, thus increasing production per unit land area (Adjei et al., 1980). Bahiagrass Cover There was a management intensity effect on percentage unit change in bahiagrass cover (P=0.02) during 2 yr of grazing. The HIGH treatment had a positive effect on percent bahiagrass cover (7.1%) and the LOW and MODERATE treatments both had a negative effect (-6.4 and -4.7%). This negative change was predominantly due to the invasion of vaseygrass (Paspalum urvillei Steud) and smutgrass [Sporobolus indicus (L.) R. Br.], both of which are bunch grass weeds. Some grass weed species such as vaseygrass are palatable to cattle at immature growing stages and are grazed (Sollenberger et al., 1997). With increasing management intensity, greater SR increases the frequency of animal visits to a given site in a pasture. This may result in more frequent grazing of herbage, including weeds, such that they remain more palatable to cattle. Newman et al. (2003) found a greater decrease of vaseygrass plant density in limpograss [Hemarthria altissima (Poir.) Stapf & Hubb.] pastures when forage was grazed to 20 cm as opposed to 40 and 60 cm. The loss in vaseygrass plant density was attributed to its inability to adequately refoliate and restore carbohydrate reserves after consecutive grazing events. This along with the low growth habit and strong ability for photosynthesis or a sizeable carbohydrate reserve from which to draw for regrowth of

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56 bahiagrass (Beaty et al., 1970) allows it to out compete the weedy bunch grasses under heavier grazing pressure. Summary and Conclusions The objectives of this research were to assess the effects of management intensity on forage and yearling beef heifer performance in Pensacola bahiagrass. For this experiment, management intensity was defined as a combination of a N fertilizer rate and an animal stocking rate and levels of intensity were chosen to reflect and extend those used by beef producers in Florida. The three management intensity treatments were LOW (40 kg N ha -1 yr -1 1.2 animal units [AU, one AU=500 kg live weight] ha -1 stocking rate), MODERATE (120 kg N ha -1 yr -1 2.4 AU ha -1 stocking rate), and HIGH (360 kg N ha -1 yr -1 3.6 AU ha -1 stocking rate), and treatments were arranged in two replicates of a randomized block design. As management intensity increased, heifer average daily gain, pasture herbage mass, and herbage allowance decreased. However, nutritive value, gain per hectare, herbage accumulation rate, and bahiagrass cover increased as a result of increased management intensity. As management intensity increased above the LOW treatment, production per unit land area increased, but at a large cost in relation to additional N cost. Gain per hectare increased 113 kg ha -1 as management intensity increased from LOW to MODERATE at an additional cost of $60 for N fertilizer (This does not include the additional cost of P and K applications for MODERATE and HIGH during 2002). This equals a cost of $0.53 of fertilizer per additional kg of gain above LOW. As management intensity increased to HIGH, there was a 173 kg ha -1 increase in gain per hectare. With the cost of additional fertilizer ($206), the cost of fertilizer per additional kg of gain equaled $1.21.

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57 From the results of this research, it is apparent that very high N rates will not produce gains that will make these strategies economically feasible for beef producers. If the need arises for producers to increase production on decreased land area, the replacement of bahiagrass with another more management responsive species will be required.

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CHAPTER 4 GRAZING METHOD EFFECTS ON FORAGE GROWTH AND NUTRITIVE VALUE OF BAHIAGRASS PASTURES Introduction High yield of high quality forage is critical for maximizing animal production on pasture. As grassland is converted to non-agricultural uses in increasingly urban states like Florida, maintaining production levels on a decreasing land resource may become difficult. Intensification of management is one option for achieving the desired increase in production per unit land area. Choice of a grazing method is an important management decision that may affect animal production on grazed pasture (Ball et al., 1996). Changing from continuous to rotational stocking has the potential to increase forage production, reduce amount of forage wasted, and in turn increase stocking rates (Blaser, 1986). This increase in stocking rate may allow for higher animal performance on a per unit land area basis. Potential exists to improve pasture performance by altering the number of pasture subdivisions, i.e., length of the grazing period in rotationally stocked pastures. Comparisons of bahiagrass pasture performance are limited under a wide range of grazing management practices. The objectives of this experiment were to evaluate the effect of continuous and a range of rotational stocking methods on herbage accumulation, herbage nutritive value, and persistence of bahiagrass. 58

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59 Methods and Materials Experiment Site The experiment was conducted at the Beef Research Unit located northeast of Gainesville, FL (29 43' N lat.). Pastures used were well-established swards of Pensacola bahiagrass that had been stocked rotationally at similar stocking rates (1.5 animal units [AU, one AU=500 kg live weight] ha -1 ) during the previous five summer grazing seasons. Soils at the site are predominantly of the Pomona and Smyrna series of sandy Spodisols with average pH of 5.7. Soil P, K, Ca, and Mg concentrations were 3, 33, 450, and 82 mg kg -1 respectively. Treatments and Design There were five treatments arranged in a randomized block design with two replicates. Treatments were continuous stocking and four rotationally stocked pastures differing only in length of grazing period (1, 3, 7, and 21 d). Length of rest period between grazings was 21 d for all four rotational stocking treatments. All pastures were fertilized at 270 and 360 kg N ha -1 in 2001 and 2002 (Table 4-1), respectively, and had a beginning stocking rate of 4.1 and 4.0 AU per hectare in the 2 yr. Table 4-1. Nitrogen application dates and rates for bahiagrass pastures. N application dates (rates in kg ha -1 ) 2001 2002 13 June (90) 30 Apr (40) 20 July (90) 14 May (50) 24 Aug (90) 12 June (90) 15 July (90) 20 Aug (90)

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60 Grazing began in the spring of 2001 and 2002 when quantity of forage was sufficient to support treatment stocking rates. Paddock size for 21-, 7-, 3-, and 1-d residence period treatments were 0.5, 0.25, 0.125, and 0.045 ha, respectively. Comparison of animal performance was not an objective of this experiment, so in effect, the area used for the rotational stocking treatments was that needed for one pasture subunit (paddock) of the complete rotational grazing system. For example, the 21-d residence period treatment would require two paddocks if animal performance was to be measured, one in which grazing would currently be underway, another which was regrowing. In this experiment, we had only one paddock per replicate. Thus during the 21-d rest periods when cattle were not grazing this paddock, they were on other treatments in the experiment. Cattle groups of the appropriate live weight were moved among the rotational stocking treatments whenever a given paddock was scheduled for grazing. In 2001, the 21-, 7-, 3-, and 1-d treatments were grazed 3, 4, 5, and 6 times respectively, while in 2002, they were grazed 4, 6, 6, and 7 times. The target stocking rate used was that of the HIGH treatment from Experiment 1 (Chapter 3), i.e., 3.6 AU ha -1 Actual rates were somewhat higher due to higher than expected cattle initial weights. Thus, all rotational treatments were stocked with approximately the same number of kg of live weight for the designated length of residence period. This resulted in very different stocking densities (short-term measure of animals per unit land area), but the stocking rate over a complete grazing cycle (time during which each paddock in an actual system would be visited once) was the same for all treatments. This allowed evaluation of the effects of the different grazing strategies on pasture accumulation rate, nutritive value, and percent bahiagrass cover.

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61 Pasture Measurements For rotationally stocked paddocks, sampling occurred the day prior to the start of each grazing period and the day the grazing period ended. Thirty disk meter measurements were taken throughout each paddock at each sampling to determine herbage mass. The disk meter was calibrated every 28 d as described in Chapter 3. Herbage accumulation was calculated as pregraze herbage mass of the current cycle minus postgraze herbage mass of the previous cycle. Herbage mass, herbage accumulation, and herbage accumulation rate for the continuous treatment were quantified as described in Chapter 3. Nutritive value for the five treatments was assessed using hand-plucked samples. The approach for the continuous treatment has already been described in Chapter 3. For the rotational stocking treatments, sampling occurred just before the beginning of each grazing period. For these treatments, herbage was sampled to a stubble that approximated what the animals would remove during the grazing period. This was based on the postgraze stubble height of recently defoliated treatments. Samples were dried at 60C for 48 h, ground to pass a 1-mm screen in a Wiley Mill, and analyzed for crude protein (CP) and in vitro organic matter digestibility (IVOMD) as described in Chapter 3. Bahiagrass cover was estimated visually at the beginning and end of each grazing season. Five equally spaced line transects were established for each paddock. Percent bahiagrass was estimated visibly at eight locations along each transect for a total of 40 observations per paddock. Data reported are changes in percent bahiagrass cover from before the experiment started through two grazing seasons later.

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62 Statistical Analyses Data representing annual averages (e.g., average herbage accumulation rate, average herbage CP and IVOMD, and change in bahiagrass cover) were analyzed using analysis of variance in PROC GLM of SAS with treatment as the main plot and year as the subplot. Data representing time trends throughout the season (herbage accumuulation rate, CP, and IVOMD) were analyzed using repeated measures analysis of variance in PROC MIXED of SAS with treatment as a fixed effect and sampling period as the repeated variable. Periods were identified because rotational treatments were grazed at different dates and different numbers of times throughout the year. The periods were early summer (25 June 11 July 2001 and 15 May 11 July 2002), mid-summer (12 July 29 August each year), and late summer (30 August21 October each year). Means for a given period represent data from one or two grazing cycles for rotational treatments, depending on treatment. Results and Discussion Herbage Accumulation Rate There was no year or year X management intensity effect on average herbage accumulation rate (P=0.33 and P=0.61), but there was an effect of management intensity (P=0.05). All the rotational treatments had greater herbage accumulation rate than the continuous treatment (Table 4-2). To maximize herbage accumulation requires maximum interception of light by leaf. This is achieved by increasing leaf area index (LAI, ratio of area of leaf in the canopy to the area of ground below) which allows for a greater proportion of radiation to be intercepted by the canopy (Chapman and Lemaire, 1993). Optimal LAI is that which allows 95 to 100% light interception (Donald, 1961), and this is achieved more quickly over time if grazing pressure is reduced. After

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63 defoliation, energy for regrowth is derived from mobilization of carbohydrate reserves (Gerrish, 1991). The rest period between defoliations allows swards to accumulate leaf area and restore carbohydrate reserves (Chaparro et al., 1996). Although not quantified in this study, the greater herbage accumulation rates for rotational treatments suggest that average LAI and canopy light interception were greater for rotationally than continuously stocked bahiagrass swards. Table 4-2. Herbage accumulation rate (HAR ) response to grazing method on bahiagrass pastures. Treatment 2001 2002 Average --------------kg ha -1 d -1 --------------Rot.-1 65 60 63 a Rot.-3 52 84 68 a Rot.-7 68 75 72 a Rot.-21 78 80 79 a Cont. 30 44 36 b LSD (0.05) 26 S.E. 6.6 There was no treatment X year interaction for HAR (P=0.61). Grazing methods are rotational (Rot.) and continuous (Cont.). The number following Rot. is the length of the grazing period in days, while the rest period was a constant 21 d for all rotational treatments. Means within a column followed by the same letter are not significantly different at the 0.05 probability level.

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64 Herbage accumulation rates of rotational treatments followed similar patterns during the 2001 grazing season, increasing from early to mid-summer, and then decreasing in early fall. The continuous treatment decreased accumulation rates throughout the grazing season (Table 4-3). The shorter grazing period treatments (1 and Table 4-3. Seasonal pasture herbage accumulation rate (HAR ) response to grazing method on bahiagrass pastures. 2001 Season 2002 Season Treatment 1 2 3 1 2 3 -------------------------------kg ha -1 d -1 ----------------------------Rot.-1 78 a # 87 a 50 ab 69 80 56 a Rot.-3 60 a 76 ab 28 ab 67 102 93 b Rot.-7 56 a 75 ab 57 ab 77 105 57 a Rot.-21 71 a 84 a 74 a 90 79 91 b Cont. 48 a 32 b 14 b 42 62 44 a S.E. 20 18 18 25 19 10 There was no treatment X year interaction for HAR (P=0.61). 2001 Seasons= 1 (25 June11 July); 2 (12 July29 August); and 3 (30 August16 October). 2002 Seasons= 1 (15 May11 July); 2 (12 July29 August); and 3 (30 August21 October). Grazing methods are rotational (Rot.) and continuous (Cont.). The number following Rot. is the length of the grazing period, while the rest period was a constant 21 d for all rotational treatments. # Means within a season followed by the same letter are not significantly different (P0.05) by repeated measures ANOVA contrasts. 3 d) experienced a more rapid decline in accumulation rate in early fall, while the longer grazing period treatments (7 and 21 d) had a less pronounced decline. The last sampling

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65 dates of the short grazing period treatments fell in early to mid-October, and herbage accumulation rates ranged from -28.6 to 16.5 kg ha -1 d -1 while the longer grazing period treatments ended in midto late September and ranged from 50.2 to 83.3 kg ha -1 d -1 This partly explains the sharper decrease in herbage accumulation for the 1and 3-d treatments as well as the overall trend toward lower total-season accumulation rates (Table 4-2). Lower accumulation rates for bahiagrass in fall have been attributed to plant responses to shorter daylength (Sinclair et al., 2003). During the 2002 season, all but the 21-d rotational treatment followed similar trends (Table 4-3), increasing from grazing initiation to mid-summer, and then decreasing to late summer/early fall. Crude Protein There was a year effect on herbage CP (P=0.02). The difference between years can be attributed in part to less N being applied in 2001 than in 2002, however, the lower N rate in 2001 was also associated with a shorter grazing season. In addition, during 2001 relatively heavy rainfall occurred the day of, and during the 3 d immediately following N application on 13 June and 20 July (26 and 43 mm, respectively). During the 2002, season rainfall the day of and 3 d following N application was less than 10 mm for all but the last application. The greater rainfall after application in 2001 may have caused N to leach through the soil more quickly making it less available for uptake, and possibly contributing to the lower CP values in 2001. There was no year X treatment or treatment effect on herbage CP (P=0.29 and P=0.24) (Table 4-4). Previous studies with bahiagrass have shown potentially large increases in production and forage N concentration with increasing N rate (Blue, 1998), however, in this trial all treatments received the same N rate and no effect of grazing method was observed. Williams and Hammond (1999) also found no differences in CP when comparing rotational (7 d grazing, 21 d rest) and

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66 Table 4-4. Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD) responses to stocking method on bahiagrass pastures. CP IVOMD Treatment 2001 2002 AVG 2001 2002 AVG ------------------g kg -1 -----------------------------------g kg -1 ----------------Rot.-1 132 144 138 a 496 555 526 a Rot.-3 140 152 146 a 500 572 536 a Rot.-7 143 148 146 a 508 513 511 a Rot.-21 148 150 149 a 514 544 529 a Cont. 133 143 138 a 453 536 493 b Average 139 b 147 a 494 b 544 a LSD (0.05) 13 18 S.E. 3.5 4.5 There was no treatment X year interaction for CP (P=0.29) or IVOMD (P=0.12). Grazing methods are rotational (Rot.) and continuous (Cont.). The number following Rot. is the length of the grazing period in days, while the rest period was a constant 21 d for all rotational treatments. Means within a column followed by the same letter are not significantly different at the 0.05 probability level. There was a year effect on CP(P=0.02) and IVOMD (P0.01). continuous stocking of bahiagrass when pastures were fertilized and stocked at the same level (70 kg N ha -1 and 2.1 to 2.4 head ha -1 respectively). Bermudagrass [Cynodon dactylon (L.) Pers.] also showed little difference in CP between rotational (15 paddocks with 1.52.5 d grazing period, and paddocks with 10-14 d grazing periods) and continuous stocking at equal levels of N and stocking rate (210 kg N ha -1 and 1.5 AU ha -1 ) (Matthews et al., 1994).

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67 Seasonal patterns in herbage CP among treatments during the 2001 grazing season followed similar trends (Table 4-5). All treatments decreased from early and mid-summer to late summer and increased in late summer. During the 2002 grazing season, the longer grazing period rotational treatments (7 and 21 d) followed a similar pattern to that in 2001. The short grazing period (1 and 3 d) rotational treatments and the continuous treatment showed little seasonality of response (Table 4-5). Table 4-5. Seasonal herbage crude protein (CP) response to grazing method on bahiagrass pastures. 2001 Season 2002 Season Treatment 1 2 3 1 2 3 ---------------------------------g kg -1 -------------------------------Rot.-1 166 ab 128 138 b 146 155 141 Rot.-3 173 a 134 146 a 155 158 148 Rot.-7 174 a 134 148 a 160 144 150 Rot.-21 167 ab 127 165 a 164 143 149 Cont. 150 b 132 137 b 144 148 146 S.E. 7.8 5.1 4.9 8.0 8.1 8.1 2001 Seasons= 1 (25 June11 July); 2 (12 July29 August); and 3 (30 August16 October). 2002 Seasons= 1 (15 May11 July); 2 (12 July29 August); and 3 (30 August21October). Grazing methods are rotational (Rot.) and continuous (Cont.). The number following Rot. is the length of the grazing period, while the rest period was a constant 21 d for all rotational treatments. Means within a season followed by the same letter are not significantly different (P0.05) by repeated measures ANOVA contrasts.

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68 In Vitro Organic Matter Digestibility There was a year effect (P0.01), but there was no year X treatment (P=0.12) interaction effect on IVOMD. Greater IVOMD in 2002 than 2001 occurred primarily due to very large differences between years from mid-summer through early fall. Reasons for this difference are not readily apparent. There was a treatment effect on IVOMD (P=0.01) because the rotational treatments had greater IVOMD than the continuous treatment (Table 4-4). At the same stocking rate, rotationally stocked animals are restricted to smaller area of pasture at a given point in time than continuously stocked animals causing animals to be less selective and graze lower in the canopy (Bransby, 1991). This may tend to reduce overall diet digestibility or it may increase it over time because it limits the build up of mature or senescent herbage. For these reasons and perhaps because it is difficult to sample a diet comparable to that selected by the animal, the literature does not show a consistent pattern of IVOMD response to grazing method. For example, Williams and Hammond (1999) found IVOMD to be similar in an experiment comparing rotational and continuous stocking on bahiagrass; however, research on bermudagrass suggests a trend toward higher IVOMD for rotational over continuous stocking (Matthews et al., 1994). During 2001, seasonal changes in IVOMD followed a similar pattern across all treatments, decreasing as the grazing season progressed (Table 4-6). This pattern could possibly be explained by the greater loss of water soluble carbohydrates associated with increased respiration due to increased temperatures associated with mid-summer and early fall (Jones, 1985). Another possible explanation could be the decrease in herbage accumulation rates as the season progressed. With lower accumulation rates, cattle are forced to graze lower in the canopy and this herbage is more mature and includes more

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69 senescent material. There were also differences among treatments during each seasonal period. During the early summer, all rotational treatments had significantly higher IVOMD than continuous. However, IVOMD for all rotational treatments, except the 21 d, decreased more severely through the season, so by early fall, only the 21-d rotational was higher than the continuous treatment. Table 4-6. Seasonal herbage in vitro organic matter digestibility (IVOMD) response to grazing method on bahiagrass pastures. 2001 Season 2002 Season Treatment 1 2 3 1 2 3 --------------------------------g kg -1 --------------------------------Rot.-1 579 a 510 a 472 ab 569 a 559 543 ab Rot.-3 599 a 520 a 450 ab 568 a 556 565 a Rot.-7 616 a 494 ab 468 ab 514 b 513 512 b Rot.-21 579 a 508 a 494 a 533 ab 544 566 a Cont. 537 b 442 b 432 b 557 ab 525 525 ab S.E. 14.5 20.0 16.9 18.5 25.9 16.5 2001 Seasons= 1 (25 June11 July); 2 (12 July29 August); and 3 (30 August16 October). 2002 Seasons= 1 (15 May11 July); 2 (12 July29 August); and 3 (30 August21October). Grazing methods are rotational (Rot.) and continuous (Cont.). The number following Rot. is the length of the grazing period, while the rest period was a constant 21 d for all rotational treatments. Means within a season followed by the same letter are not significantly different (P0.05) by repeated measures ANOVA contrasts. During the 2002 season, all treatments decreased or remained relatively constant in IVOMD from late spring/early summer to fall except for the 21-d treatment which increased as the season progressed (Table 4-6). During late spring/early summer,

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70 IVOMD for the 1and 3-d rotational treatments was higher than for the 7-d treatment. During the mid-summer there were no differences among treatments. By the early fall, the 1-d treatment had decreased, and the 21-d treatment had increased so that the 3and 21-d treatments were higher than the 7-d treatment (Table 4-6). Bahiagrass Cover Grazing method affected bahiagrass cover (P0.01). Continuous stocking had a positive effect on bahiagrass cover while all rotational treatments caused bahiagrass cover to decrease, especially the 1-d treatment (Table 4-7). This response was Table 4-7. Changes in bahiagrass cover in response to grazing method in bahiagrass pastures. Treatment June 2001 December 2002 Change --------------------%-------------------Rot.-1 96.2 80.6 -15.6 a Rot.-3 84.9 81.2 -3.7 b Rot.-7 85.1 80.5 -4.6 b Rot.-21 88.8 80.4 -8.4 b Cont. 80.6 87.7 7.1 c LSD (0.05) 6.7 S.E. 1.7 Grazing methods are rotational (Rot.) and continuous (Cont.). The number following Rot. is the length of the grazing period, while the rest period was a constant 21 d for all rotational treatments. Means followed by the same letter are not significantly different (P0.05) by LSD ANOVA contrast

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71 unexpected, even for a very grazing tolerant species like bahiagrass. Stocking rate was the same across treatments, so it should not have affected the response. Herbage accumulation rate was actually greater on the rotational treatments, so grazing pressure was less than on the continuous treatment. The major change in species composition of the rotational pastures was greater presence of vaseygrass (Paspalum urvillei Steud.) and smutgrass [Sporobolus indicus (L.) R. Br.]. Both of these species become unpalatable to livestock at relative young growth stages (Newman et al., 2003; Adjei et al., 2003). It can be hypothesized that the more frequent visits by cattle to a particular grazing station under continuous stocking may result in these species being kept in check to a greater degree than under a 21-d rest period rotational system. It is not clear, however, why bahiagrass cover decreased to a greater extent on the 1-d treatment than the other rotational pastures. Summary and Conclusions As agricultural land continues to diminish due to conversion to urbanized area by the increasing human population, increasing animal production per unit land area may become more and more important to producers in order to maintain financial stability. Stocking rate decisions greatly affect animal productivity, but stocking method also has the potential to influence animal performance. The objectives of this experiment were to evaluate the effect of continuous and a range of rotational stocking methods on herbage accumulation rate, herbage nutritive value, and persistence of bahiagrass pastures. Herbage accumulation and herbage IVOMD were greater for rotationally than continuously stocked pastures. Herbage accumulation rate did not differ among rotational treatments, and there was no effect of grazing method on CP. Bahiagrass cover decreased for rotationally stocked pastures (

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72 8.1% average among rotational treatments) but increased under continuous stocking (7.1%). Among rotational treatments, bahiagrass cover decreased more for the 1-d than the average of the other three treatments (-5.6 to -15.6%). With the utilization of rotational as opposed to continuous stocking, there is potential to increase herbage growth rates which in turn, could support greater stocking rates. However high N fertilization combined with rotational grazing appears to pose the threat of increased invasion of vaseygrass and smutgrass in bahiagrass pastures, thus necessitating more intensive weed control management as well. These data show no consistent advantage in any production response of very short grazing periods (1 or 3 d) on rotationally stocked bahiagrass pastures.

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CHAPTER 5 SUMMARY AND CONCLUSIONS The beef industry is a critical component of Floridas large agriculture industry. Revenues from the beef cattle industry in Florida totaled 371 million dollars in 2000 and accounted for 5.3% of the total agricultural cash receipts (Florida Agricultural Facts Directory, 2002). Grasslands cover large areas of land in both Florida and the southeastern USA and are an important source of feed to the livestock industry. Bahiagrass serves as an essential resource to the beef industry covering approximately 1 million hectares in Florida (Chambliss, 2000). However, with the large increase in human population over the past 40 yr and projected increases in the next 30 yr, urbanization poses a threat to the amount of land available for agricultural uses. The livestock industry may be forced to maintain economic livelihood on smaller amounts of land. A potential solution to this problem is to increase management intensity on smaller amounts of land to attain equal or greater production. With this situation in mind, the research conducted focused on animal performance and pasture characteristics of grazed bahiagrass pastures as influenced by increasing management intensity. Management intensity was defined by stocking rate, N fertilization rate, and grazing method, and the research was divided into two experiments. The first experiment evaluated beef heifer performance and pasture responses to three levels of management intensity of continuously stocked bahiagrass pastures. Intensity levels were defined by N fertilizer rate and stocking rate and included LOW (40 kg N ha -1 yr -1 1.2 animal units [AU, one AU=500 kg live weight] ha -1 stocking rate), 73

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74 MODERATE (120 kg N ha -1 yr -1 2.4 AU ha -1 stocking rate), and HIGH (360 kg N ha -1 yr -1 3.6 AU ha -1 stocking rate), and were intended to represent and extend the current practice of producers in Florida. Animal performance was evaluated on a per animal basis (average daily gain) and a per unit land area basis (gain per hectare). Pasture responses included nutritive value, herbage mass, herbage allowance, and herbage accumulation. As management intensity increased, heifer average daily gain and pasture herbage mass and allowance decreased. However, gain per hectare, herbage nutritive value, herbage accumulation rate, and bahiagrass cover increased as a result of increased management intensity. Both herbage mass and allowance decreased as management intensity increased above the LOW to the HIGH treatment (3.0 to 2.6 Mg ha -1 and 4.0 to 1.1 kg forage kg -1 an. wt., respectively) as a result of the greater proportional increase in stocking rates compared to accumulation rate. Heifer ADG and pasture herbage mass and allowance generally followed similar trends throughout the season. Heifer ADG decreased, but the response was relatively small, only decreasing 0.10 kg d -1 as management intensity increased from the LOW to HIGH treatment. Both herbage CP and IVOMD increased as management intensity increased. Increases in CP (97 to 138 g kg -1 ) from the LOW to HIGH treatment were caused in part by the increase in N application. The observed increase in herbage IVOMD from the LOW to HIGH treatment (452 to 495 g kg -1 ) is not a typical response to increased N fertilization, but it can be explained by the increase in SR which likely increased the frequency of visits per site in the pasture. This prevented underutilization and accumulation of mature herbage.

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75 Production per unit land area increased as management intensity increased above the LOW treatment, but at a large cost in relation to additional N cost. As management intensity increased from the LOW to the MODERATE level, gain per hectare increased 110 kg ha -1 However with the cost of additional N being 60 dollars, the cost of fertilizer per additional kg of gain was $0.55. As management intensity increased from LOW to HIGH, gain per hectare increased 170 kg ha -1 The cost of additional N was $206; therefore the cost of fertilizer per additional kg of gain was $1.21. From this it is apparent that very high N rates on bahiagrass are not likely to be economically feasible for beef producers. The second experiment evaluated continuous and a range of rotational stocking methods on herbage accumulation rate, herbage nutritive value, and persistence of bahiagrass pastures. In this experiment there were five treatments, including four rotational treatments differing only in length of the grazing period, and one continuous stocking treatment. The rotational treatments had grazing periods of 1, 3, 7, and 21-d, all with a 21 d rest period. All treatments received the same N fertilization and stocking rate of the HIGH treatment from the first experiment. Changing from continuous to rotational stocking increased herbage accumulation and IVOMD. There were no differences among rotational treatments in herbage accumulation rate; however, there was a trend toward increasing accumulation rate as length of grazing period increased (63 to 79 kg ha -1 d -1 ). Use of rotational compared with continuous stocking decreased bahiagrass cover (-8.1% average among rotational treatments compared to +7.1% for continuous). Among rotational treatments, bahiagrass

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76 cover decreased more for the 1-d treatment than for the other grazing periods (-15.6 % vs. -3.7). These treatments had no effect on herbage CP. These experiments showed that bahiagrass pastures were responsive to increased management intensity, but high levels of N fertilization appear to be associated with significant concerns including insufficient increase in animal production relative to N costs, greater weed invasion with rotational stocking, and, although not an objective of these experiments, greater potential for loss of nutrients to the environment. Rotational stocking increased herbage accumulation rate, which in practice would allow for a greater stocking rate and production per unit land area, but rotational stocking in conjunction with high N fertilizer rates resulted in large increases in cover by vaseygrass and smutgrass. Among rotational stocking treatments, there were no measurable advantages to increasing the number of paddocks (decreasing the grazing time per paddock) per pasture. In conclusion, these data suggest that modest increases in management intensity of bahiagrass pastures may be warranted, specifically rotational stocking (2-4 paddocks) and increasing N rate to approximately 120 kg ha -1 yr -1 However, higher rates of N fertilizer do not appear to have merit from either an economic or a pasture-persistence perspective in addition to increase potential for negative environmental impacts. Therefore, if the need for increased production per unit land areas becomes acute in Florida forage-livestock systems, the use of other more management-responsive grasses will likely be required. This research also points to the need for further research in related areas. There is the possibility of imposing these or similar management practices on one or more forage species that have the potential to respond more favorably than bahiagrass. This research

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77 may provide useful data for development of models that can be helpful in assessing sustainability in an increasingly urban society.

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LIST OF REFERENCES Adjei, M.B., P. Mislevy, R. Kalmbacher, and P. Busey. 1989. Production, quality, and persistence of tropical grasses as influenced by grazing frequency. Soil Crop Sci. Soc. Fla Proc. 48:1-6. Adjei, M.B., P. Mislevy, K.H. Quesenberry, and W.R. Ocumpaugh. 1988. Grazing-frequency effects on forage production, quality, persistence and crown total non-structural carbohydrate reserves of limpograss. Soil Crop Sci. Soc. Fla Proc. 47:233-236. Adjei, M.B., P. Mislevy, and C.Y. Ward. 1980. Response of tropical grasses to stocking rate. Agron. J. 72:863-868. Adjei, M.B., J.J. Mullahey, P. Mislevy, and R. Kalmbacher. 2003. Smutgrass control in perennial grass pastures. Univ. of Fla SS-AGR-18. Arndorfer, B. 2003. County projected to grow by 41 percent, pp. 1 The Gainesville Sun, Final Edition, Gainesville, FL. 12 Feb. Ball, D.M., C.S. Hoveland, and G.D. Lacefield. 1996. Grazing management, p. 182-196. In Southern Forages, 2nd ed. Potash and Phosphate Institute, Norcross, GA. Beaty, E.R., R.H. Brown, and J.B. Morris. 1970. Response of Pensacola bahiagrass to intense clipping. p. 538-542. In M.J.T. Norman (ed.) Proc. Int. Grassl Congr., 11 th Surfers Paradise, Qld., Australia. 13-23 Apr. 1970. Univ. of Qld. Press, Santa Lucia, Qld., Australia. Beaty, E.R., J.L. Engel, and J.D. Powell. 1977. Yield, leaf growth, and tillering in bahiagrass by N rate and season. Agron. J. 69:308-311. Blaser, R.E. 1986. Forage-animal management systems. Virginia Agric. Exp. Stn. Bull. 86-7, Blacksburg, VA 24061. Blue, W.G. 1988. Response of Pensacola bahiagrass on a Florida spodosol to nitrogen sources and times of application. Soil Crop Sci. Soc. Fla Proc. 47:139-142. Blue, W.G., C.L. Dantzman, and V. Impithuksa. 1980. The response of three perennial warm-season grasses to fertilizer Nitrogen on an eaugallie fine sand (Alfic Haplaquod) in central Florida. Special Report, Ag. Exp. Stn., Univ. of Ark. 9:44-47. 78

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79 Bransby, D.I. 1991. Implications of rotational and continuous grazing: a case for continuous grazing. p. 10-14 In Proc. Am. Forage Grassl. Conf., Columbia, MO. 1-4. Apr. 1991. Am. Forage Grassl. Council, Georgetown, TX. Burns, J.C., J.G. McIvor, L. Villalobos M., R.R. Vera, and D.I. Bransby. 2003. Grazing systems. In L.E. Moser et al. (ed.) Warm-season (C 4 ) grasses. ASA, CSSA. Madison, WI. Burson, B., and V. Watson. 1995. Bahiagrass, dallisgrass, and other Paspalum species, p. 431-434, In R. Barnes et al., (eds.) Forages Volume I: An Introduction to Grassland Agriculture. Iowa State University Press, Ames, Iowa. Burton, G.W., R.N. Gates, and G.J. Gascho. 1997. Response of Pensacola bahiagrass to rates of nitrogen, phosphorus and potassium fertilizers. Soil Crop Sci. Soc. Fla Proc. 56:31-35. Chambliss, C. 2000. Bahiagrass. UFL SS-AGR-36. Univ. of Fla. Gainesville, FL. Chaparro, C.J., L.E. Sollenberger, and K.H. Quesenberry. 1996. Light interception, reserve status, and persistence of clipped Mott elephantgrass swards. Crop Sci. 36:649-655. Chapman, D.F., and G. Lemaire. 1993. Morphogenetic and structural determinants of plant regrowth after defoliation. p. 95-104. In Proc. Int. Grassl. Congr., 17 th Rockhampton, Australia. 8-21 Feb. 1993. Dunmore Press Ltd., Palmerston North, New Zealand. Christiansen, S., O.C. Ruelke, W.R. Ocumpaugh, K.H. Quesenberry, and J.E. Moore. 1988. Seasonal yield and quality of 'Bigalta', 'Redalta' and 'Floralta' limpograss. Trop. Ag. 65:49-55. Conrad, B.E., E.C. Holt, and W.C. Ellis. 1981. Steer performance on Coastal, Callie and other hybrid bermudagrasses. J. Anim. Sci. 53:1188-1192. Cuomo, G.J., D.C. Blouin, D.L. Corkern, and J.E. McCoy. 1996. Plant morphology and forage nutritive value of three bahiagrasses as afected by harvest frequency. Agron J 88:85-89. DiRienzo, D.B., K.E. Webb Jr., D.E. Brann, and M.M. Alley. 1991. Effect of spring nitrogen application on barley forage yields and silage fermentation. J. Prod. Agric. 4:39-44. Donald, C.M. 1961. Competition for light in crops and pastures. Symposium of the Soc. of Exp. Bio. 15:282-313. Faria, J.R., B. Gonzalez, J. Faria-Marmol, and D.E. Morillo. 1999. Effect of nitrogen and phosphorus fertilizers on some components of nutritive value of dwarf elephantgrass. Comm. Soil Sci. Plant Anal. 30:2259-2266.

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80 Florida Dept. of Ag. and Cons. Services. 2002. Agricultural Fast Facts. Tallahassee, FL. Gallaher, R.N., C.O. Weldon, and J.G. Futral. 1975. An aluminum digester for plant and soil analysis. Soil Crop Sci. Soc. Amer Proc. 39:803-806. Gates, R.N., G.M. Hill, and G.W. Burton. 1999. Response of selected and unselected bahiagrass populations to defoliation. Agron. J. 91:787-795. Gates, R.N., C.L. Quarin, and C.G.S. Pedreira. 2004. Bahiagrass, In L. E. Moser et al., (eds.). Warm season (C 4 ) grasses monograph. ASA/CSSA, Madison, WI. (in press). George, J.R., G.S. Reigh, R.E. Mullen, and J.J. Hunczak. 1990. Switchgrass herbage and seed yield and quality with partial spring defoliation. Crop Sci. 30:845-849. Gerrish, J.R. 1991. Biological implications of rotational grazing. p. 6-9. Proc. Am. Forage Grassl. Conf. In Proc. Am. Forage Grassl. Conf., Columbia, MO. 1-4 Apr. 1991. Am. Forage Grassl. Council, Georgetown, TX. Hammond, C. 1994. Animal Waste and the Environment. Circular 827. Univ. of Ga. Athens, GA. Hammond, A.C., M.J. Williams, T.A. Olson, L.C. Gasbarre, E.A. Leighton, and M.A. Menchaca. 1997. Effect of rotational vs. continuous intensive stocking of bahiagrass on performance of Angus cows and calves and interaction with sire type on gastrointestinal nematode burden. J. of Anim. Sci. 75:2291-2299. Hernandez Garay, A., L.E. Sollenberger, D.C. McDonald, G.J. Ruegsegger, R. Kalmbacher, and P. Mislevy. in review. Nitrogen fertilization and stocking rate affect stargrass pasture and cattle performance. Johnson, C.R., B.A. Reiling, P. Mislevy, and M.B. Hall. 2001. Effects of nitrogen fertilization and harvest date on yield, digestibility, fiber, and protein fractions of tropical grasses. J. Anim. Sci. 79:2439-2448. Jones, C.A. 1985. Temperature. p. 140-149. In C.A. Jones (eds.) C4 grasses and cereals: Growth, development, and stress response. John Wiley & Son, New York. Lima, G.F.da C., L.E. Sollenberger, W. Kunkle, J.E. Moore, and A.C. Hammond. 1999. Nitrogen fertilization and supplementation effects on performance of beef heifers grazing limpograss. Crop Sci. 39:1853-158. Lorenz, R.J., and G.A. Rogler. 1972. Forage production and botanical composition of mixed prairie as influenced by nitrogen and phosphorus fertilization. Agron. J. 64:244-248. Mathews, B.W., L.E. Sollenberger, and C.R. Staples. 1994. Dairy heifer and bermudagrass pasture responses to rotational and continuous stocking. J. Dairy Sci. 77:244-252.

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81 Matches, A.G. 1992. Plant response to grazing: A review. J. Prod. Agric. 5:1-7. Mislevy, P. 1985. Forages for grazing systems in warm climates. p. 122-129. In L. R. M. Dowell (ed.). Nutrition of grazing ruminants in warm climates. Academic Press, Orlando, FL. Mislevy, P., and W.F. Brown. 1991. Management and utilization of complementary forages: Stargrass. 40 th Florida Beef Cattle Short Course. Univ. of Fla., Gainesville. Moore, J.E., and G.O. Mott. 1974. Recovery of residual organic matter from in vitro digestion of forages. J. Dairy Sci. 57:1258-1259. Mott, G.O., and H.L. Lucas. 1952. The design, conduct, and interpretation of grazing trials on cultivated and improved pastures. p. 1380-1385. In Proc. Int. Grassl. Congr., 6 th 17-23 Aug. 1952, State College, PA. Pennsylvania State Univ., State College, PA. Moyer, J.L., D.W. Sweeney, and R.E. Lamond. 1995. Response of tall fescue to fertilizer placement at different levels of phosphorus, potassium, and soil pH. J. Plant Nut. 18:729-746. Muchovej, R.M., and J.J. Mullahey. 2000. Yield and quality of five bahiagrass cultivars in southwest Florida. Soil Crop Sci. Soc. Fla Proc. 59:82-84. Muchovej, R.M., and J.E. Rechcigl. 1994. Imact of nitrogen fertilization of pastures and turfgrasses on water quality. p. 91-135. In B.A. Stewart and R. Lal (eds.). Soil processes and water quality. Lewis Publishers Inc., Boca Raton, FL. Newman, Y.C., L.E. Sollenberger, and C.G. Chambliss. 2003. Canopy height effects on vaseygrass and bermudagrass spread in limpograss pastures. Agron. J. 95:390-394. Nichols, J.T., P.E. Reece, G.W. Hergert, and L.E. Moser. 1990. Yield and quality response of subirrigated meadow vegetation to nitrogen, phosphorus and sulfur fertilizer. Agron. J. 54:47-52. Pitman, W.D., D.D. Redfearn, and J.C. Read. 2000. Response of Texas bluegrass to season of nitrogen fertilization on the Louisiana Coastal Plain. J. Plant. Nut. 23:423-429. Prates, E.R., H.L Chapman, Jr., E.M. Hodges, and J.E. Moore. 1975. Animal performance by steers grazing 'Pensacola' bahiagrass pasture in relation to forage production, forage composition, and estimated intake. Soil Crop Sci. Soc. Fla Proc. 34:152-155. Prine, G.M., and G.W. Burton. 1956. The effect of nitrogen rate and clipping frequency upon the yield, protein content and certain morphological characteristics of coastal bermudagrass. Agron. J. 48:296-301.

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82 Ruelke, O.C., and G.M. Prine. 1971. Performance of six hybrid bermudagrass, Pangola digitgrass, and Pensacola bahiagrass at three fertility levels in north Central Florida. Soil Crop Sci. Soc. Fla Proc. 31:67-71. SAS Inst. Inc. 1996. SAS statistics user's guide. Release Version 6. SAS Inst. Inc., Cary, NC. Sinclair, T.R., J.D. Ray, P. Mislevy, and L.M. Premazzi. 2003. Growth of subtropical forage grasses under extended photoperiod kuring short-daylength months. Crop Sci. 43:618-623. Sollenberger, L.E. 2001. Tropical legume and grass characteristics. Notes from AGR 6233, Univ. of Fla. Sollenberger, L.E., G.F.da C. Lima, J.F. Holderbaum, W.E. Kunkle, J.E. Moore, and A.C. Hammond. 1997. Cattle wight gain and sward-animal nitrogen relationships in grazed Hemarthria altissima pastures. p. 43-44. In Proc. Int. Grassl. Congress, 18 th Winnipeg, MB, and Saskatoon, SK, Canada. 8-17 June. Grasslands 2000, Toronto. Sollenberger, L.E., W.R. Ocumpaugh, V.P.B. Euclides, J.E. Moore, K.H. Quesenberry, and C.S. Jones, Jr. 1988. Animal performance on continuously stocked Pensacola bahiagrass and Floralta limpograss. J. Prod. Agric. 1:216-220. Sollenberger, L.E., G.A. Rusland, C.S. Jones, Jr., K.A. Albrecht, and K.L. Gieger. 1989. Animal and forage responses on rotationally grazed 'Floralta' limpograss and 'Pensacola' bahiagrass pastures. Agron. J. 81:760-764. Springer, T.L., and C.M. Taliaferro. 2001. Nitrogen fertilization of buffalograss. Crop Sci. 41:139-142. Stanley, R. L., Jr. 1994. Resonse of 'Tifton 9' Pensacola bahiagrass to harvest interval and nitrogen rate. Soil Crop Sci. Soc. Fla Proc. 53:80-81. Stanley, R.L., E.R. Beaty, and J.D. Powell. 1977. Forage yield and percent cell wall constituents of Pensacola bahiagrass as related to N fertilization and clipping height. Agron. J. 69:501-504. Sumner, S., W. Wade, J. Selph, J. Southwell, V. Hoge, P. Hogue, E. Jennings, P. Miller, and T. Seawright. 1991. Fertilization of established bahiagrass pasture in Florida. Univ. of FL Cir. 916. Tharel, L.M. 1989. Rotational grazing on three bermudagrass cultivars. Special Report, Ag. Exp. Stn., Univ. of Ark.:17-19. Thom, W.O., H.B. Rice, M. Collins, and R.M. Morrison. 1990. Effect of applied fertilizer on Tifton 44 bermudagrass. J. Prod. Agric. 3:498-501.

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83 Twidwell, E., W.D. Pitman, and G.J. Cuomo. 1998. Bahiagrass production and management. LSU publication # 2697. Tyagi, G.D., and V. Singh. 1986. Effect of cutting management and nitrogen fertilization on yield and quality of Pennisetum pedicellatum Trin. (Dinanath grass). Trop. Agric. 63:121-124. U.S. Census Bureau. 2002. State and County QuickFacts: Florida. http://quickfacts.census.gov. 24 May, 2003. Utley, P R, H.D. Chapman, W.G. Monson, W.H. Marchant ,and W.C. McCormick. 1974. Coastcross-I bermuda grass, Coastal bermuda grass and Pensacola bahiagrass as summer pasture for steers. J. Anim. Sci. 38: 490-495. Velez-Santiago, J., and J.A. Arroyo-Aguilu. 1983. Nitrogen fertilization and cutting frequency, yield and chemical composition of five tropical grasses. J. Agric. Univ. Puerto Rico 67:61-69. Wiedenfeld, R.P. 1988. Coastal bermudagrass and Renner lovegrass fertilization responses in a subtropical climate. J. Range Mange. 41:7-11. Williams, M.J., and A.C. Hammond. 1999. Rotational vs. continuous intensive stocking management of bahiagrass pasture for cows and calves. Agron. J. 91:11-16. Wilson, J.R. 1983. Effects of water stress on herbage quality. p. 470-472. In J.A. Smith and V.W. Hays (eds.) Proc. Int. Grassl Cong, 14 th .15-24 June 1981, Lexington, KY Zhang, Y., L.D. Bunting, L.C. Kappel, and J. Hafley. 1995. Influence of nitrogen fertilization and defoliation frequency on nitrogen constituents and feeding value of annual ryegrass. J. Anim. Sci. 72:2474-2482.

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BIOGRAPHICAL SKETCH R. Lawton Stewart, Jr. was born 29 June 1979, in Columbus, Mississippi, and grew up in Tifton, Georgia. Lawton received a B.S. in animal and dairy science at the University of Georgia. A member of Gamma Sigma Delta honor society, Lawton plans to pursue a Doctor of Philosophy in animal science at Virginia Polytechnic Institute and State University upon completion of his Master of Science in agronomy. At VPI, where he is the recipient of the J.L. Pratt fellowship, Lawton plans to study ruminant nutrition. 84


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MANAGEMENT INTENSITY EFFECTS ON ANIMAL PERFORMANCE AND
HERBAGE RESPONSE IN BAHIAGRASS PASTURES















By

R. LAWTON STEWART, JR.


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2003


































Copyright 2003

by

R. Lawton Stewart, Jr.

































To my wife Beth.















ACKNOWLEDGMENTS

The author would like to begin by thanking Dr. Lynn E. Sollenberger, chairman of

the supervisory committee and mentor. His guidance and direction throughout the

graduate school programs and the writing of this thesis have been greatly appreciated.

Also thanks go to the rest of the advisory committee, Dr. Martin B. Adjei, Dr. Carrol G.

Chambliss, and Dr. Adegbola Adesogan, for their willingness to serve on the graduate

committee, thoughtful input, and for reviewing the thesis.

Thanks are also due to many who assisted in both field and lab tasks. They include

fellow graduate students Jose Dubeux and Joa6 Vendramini, who spent hours upon hours

at the Beef Research Unit helping collect data, Sid Jones and Dwight Thomas, at the

Forage Evaluation Field Laboratory, for providing valuable help with field exercises, and

Richard Fethiere and the crew of the Forage Evaluation Support Laboratory, for

assistance in sample analysis. Dr. Yoana C. Newman provided excellent advice on topics

ranging from field techniques to statistical analyses. Also thanks are expressed to Dr.

Jerry M. Bennett, department chair, and Dr. David S. Wofford, graduate coordinator, for

the opportunity to study in the Agronomy Department.

Thanks are due to fellow graduate students Deke Alkire, Nathan and Wimberley

Krueger, Brad Austin, Sindy Interrante, Paul Davis, Marcia Grise, and others for their

help, but more importantly for their friendship over the past two years.

Last, but not least, the author would like to thank his family. His wife, Beth, was

supportive of his decisions and many tasks throughout graduate school. Also, his parents,









Robert and Martha Stewart, have always emphasized the importance of education and

have been encouraging throughout the many educational processes. Also thanks go to the

two best sisters in the world, Kate and Sally.
















TABLE OF CONTENTS
page

A C K N O W L E D G M E N T S ................................................................................................. iv

LIST OF TA BLE S ............. ........... ... .. ...... ................ ... .... ... .............. viii

LIST OF FIGURES ................................. ...... ... ................. .x

ABSTRACT ........ .............. ............. ...... .......... .......... xi

CHAPTER

1 IN TRODU CTION ................................................. ...... .................

2 LITER A TU R E R EV IEW .............................................................. ...................... 5

C characteristics of B ahiagrass....................................... .......................................5
G e n e ra l ....................................................... 5
Y field .......................................................................... . 6
N utritiv e V alu e ....................................................... 7
A nim al P perform an ce ................................................................. ............... 8
Nitrogen Fertilization...................................9
C ool-Season and N ative G rasses .........................................................................9
Tropical G rasses .......................................... .................. .. ............... 11
B ah iag ra ss ................... ...................1...................4.......
Environm mental Im plications ......................................... ............... 15
G razing M anagem ent ........................................................................ 16
Grazing M ethod ..................................... ........ ................... 16
Grazing Frequency .................................. ................ ........ .. 18
Grazing Intensity .................................... ........................ .... 20
S u m m ary ......................................................................................................... 2 2

3 HERBAGE AND ANIMAL PERFORMANCE RESPONSES TO MANAGEMENT
INTENSITY OF CONTINUOUSLY STOCKED BAHIAGRASS PASTURES ......23

In tro d u ctio n .......................................................................................2 3
M methods and M materials ............. ..................... ..........................................24
Experim mental Site .................................... ........................ ...24
Treatments and Design ............................................... ........................25
Pasture and Anim al M anagem ent.......... .......................... ........ .. ...... .... 26
P astu re R esp on ses ..................................................................... ....................2 9









A nim al R responses ..................................... .......... ........ .. ............
Statistical A analysis ...................................... ................ ............ 3
R results and D iscu ssion .............................. ........................ .. ...... .... ...... ...... 32
H erb ag e M ass .......................................................... 33
H erbage A ccum ulation R ate.......................................... ........... ............... 34
Crude Protein ................................. ..... ........ ......... ...............40
In V itro Organic M atter D igestibility............................................................... 44
H erbage A llow ance ........................ .. ....................... ...... .. ........... 47
Average Daily Gain .................. .......................... .... .... .................. 49
G ain per H ectare ....................................................... ................. 53
B ahiagrass C ov er............. ........................................ .............. .. .... ..... .55
Sum m ary and C onclu sions .............................................................. .....................56

4 GRAZING METHOD EFFECTS ON FORAGE GROWTH AND NUTRITIVE
VALUE OF BAHIAGRASS PASTURES ...................................... ............... 58

Introduction................................. .................................. ........... 58
M methods and M materials .............................. ......................... ... ........ .... ............59
Experim ent Site .................................. ........ .. .... ...............59
Treatm ents and Design ........................................ ......... ................... 59
Pasture Measurements ............................ ............ ..................... 61
Statistical A n aly ses........... ................................................ .......... ..... .... .... 62
R results and D iscu ssion .............................. ........................ .. ...... .... ...... ...... 62
H erbage A ccum ulation R ate.......................................... ........... ............... 62
C rude P rotein ................................................................................................ 65
In Vitro Organic Matter Digestibility......................................................68
B ahiagrass C ov er............. ........................................ .............. .. .... ..... .70
Sum m ary and C onclu sions .............................................................. .....................7 1

5 SUMMARY AND CONCLUSIONS.....................................................................73

L IST O F R E FE R E N C E S ............................................................................. ............. 78

B IO G R A PH IC A L SK E TCH ..................................................................... ..................84
















LIST OF TABLES


Table pge

3-1 List of actual stocking rates (SR) of continuously stocked bahiagrass pastures....26

3-2 Rainfall at the experiment site for years 2001-2002 and the 30-yr average for
G ainesville, F L ......................................................................27

3-3 Nitrogen application dates on continuously stocked bahiagrass pastures. ............28

3-4 Composition of mineral supplem ent ........................................... ............... 28

3-5 Herbage mass double sample regression equations....................... ...............30

3-6 Monthly temperatures at the experiment site for years 2001-2002 ....................32

3-7 Pasture herbage mass (HM) and herbage accumulation rate (HAR) responses to
management intensity of continuously stocked bahiagrass pastures ...................34

3-8 Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD)
responses to management intensity of continuously stocked bahiagrass
p astu res. ......................................................... ................ 4 1

3-9 Herbage allowance response to management intensity. ......................................49

3-10 Heifer average daily gain (ADG) and gain per hectare (GPH) responses to
m anagem ent intensity. ........................................... ........................ .....51

4-1 Nitrogen application dates and rates for bahiagrass pastures. ............................59

4-2 Herbage accumulation rate (HARt) response to grazing method on bahiagrass
p astu res. ......................................................... ................ 6 3

4-3 Seasonal pasture herbage accumulation rate (HARt) response to grazing method
on b ahiagrass pastu res.......... .......................................................... .. .... ... ....64

4-4 Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD)
responses to stocking method on bahiagrass pastures. ........................................66

4-5 Seasonal herbage crude protein (CP) response to grazing method on bahiagrass
p astu res. ......................................................... ................ 6 7









4-6 Seasonal herbage in vitro organic matter digestibility (IVOMD) response to
grazing m ethod on bahiagrass pastures....................................... ............... 69

4-7 Changes in bahiagrass cover in response to grazing method in bahiagrass
p astu res. ......................................................... ................ 7 0















LIST OF FIGURES


Figure page

3-1 Herbage mass (HM) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2001.............................................. 35

3-2 Herbage mass (HM) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2002..................................... 36

3-3 Herbage accumulation rate (HAR) response to three levels of management
intensity on continuously stocked bahiagrass pastures in 2001...........................38

3-4 Herbage accumulation rate (HAR) response to three levels of management
intensity on continuously stocked bahiagrass pastures in 2002 ..........................39

3-5 Herbage crude protein (CP) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2001..............................................42

3-6 Herbage crude protein (CP) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2002..................................... 43

3-7 Herbage in vitro organic matter digestibility (IVOMD) response to three levels
of management intensity on continuously stocked bahiagrass pastures in 2001...45

3-8 Herbage in vitro organic matter digestibility (IVOMD) response to three levels
of management intensity on continuously stocked bahiagrass pastures in 2002...46

3-9 Herbage allowance (HA) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2001......... .........................48

3-10 Herbage allowance (HA) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2002..................................... 50

3-11 Yearling beef heifer cumulative average daily gain (ADG) response to three
levels of management intensity on continuously stocked bahiagrass pastures in
200 1 ........................ ......... .. ..........................................52

3-12 Yearling beef heifer cumulative average daily gain (ADG) response to three
levels of management intensity on continuously stocked bahiagrass pastures in
2 0 0 2 .......................................................................... 5 4















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

MANAGEMENT INTENSITY EFFECTS ON ANIMAL PERFORMANCE AND
HERBAGE RESPONSE IN BAHIAGRASS PASTURES
By

R. Lawton Stewart, Jr.

August 2003

Chairman: Lynn E. Sollenberger
Major Department: Agronomy

Bahiagrass (Paspalum notatum Flugge) pasture covers approximately one million

hectares in Florida, 90% of which is utilized by beef cattle. Urbanization may force beef

producers to achieve economic livelihood on reduced land area. One option for producers

is to increase intensity of management of the remaining pasture resource. The objectives

of this research were 1) to evaluate the effects of management intensity (MI), defined as

combinations of N fertilization and stocking rates (SR), on yearling beef heifer and

bahiagrass pasture performance (Exp. 1), and 2) to evaluate bahiagrass forage responses

to continuous and rotational stocking (Exp. 2). Treatments in Exp. 1 included LOW (40

kg N ha-1 yr-1, 1.2 animal units [AU, one AU=500 kg live weight] ha-1 SR), MODERATE

(120 kg N ha-1 yr-1, 2.4 AU ha1 SR), and HIGH MI (360 kg N ha-1 yr1, 3.6 AU ha-1 SR).

Treatments in Exp. 2 were continuous stocking, and rotational stocking with 1-, 3-, 7-,

and 21-d grazing periods. All rotational treatments had a 21-d rest period.









Herbage mass (3.0 Mg ha-1) and herbage allowance (4.0 kg forage kg-1 animal

weight) in Exp. 1 were greater for LOW and decreased as MI increased to HIGH (2.6 Mg

ha-1 and 1.1 kg forage kg-1 animal weight). This occurred despite herbage accumulation

rate being greater for HIGH (33 kg ha-1 d-1) than LOW (19 kg ha-1 d-1). Nutritive value

increased with increasing MI, in part because of greater N rate and also because the

higher stocking rates likely increased the frequency at which cattle revisited grazing

locations. Average daily gain decreased from LOW to HIGH (0.46 to 0.36 kg d-1)

because of the decrease in herbage allowance for HIGH. Gain per hectare increased with

increasing MI due to a greater utilization of the forage present. Bahiagrass cover

increased with the HIGH MI (7.1%) and decreased with LOW (-6.4) and MODERATE (-

4.7%). Decreases in cover were associated with the invasion ofvaseygrass (Paspalum

urvillei) and smutgrass (Sporobolus indicus) and occurred because of decreased grazing

pressure that allowed these species to mature and become unpalatable to cattle.

In Exp. 2, rotational stocking increased herbage accumulation rate and digestibility

over continuous stocking, but it had no effect on herbage crude protein. Continuous

stocking resulted in greater bahiagrass cover, while rotational stocking led to reduced

cover due to the encroachment of vaseygrass and smutgrass.

These experiments demonstrated increased bahiagrass production and quality with

increasing management intensity. However, the magnitude of these improvements is not

sufficient to compensate for the additional costs associated with greater management

intensity above MODERATE and the greater risk of damage to the environment.

Therefore, if the need for increased production per unit land area becomes acute, the use

of another more management-responsive grass species likely will be required.














CHAPTER 1
INTRODUCTION

Grasslands occupy large areas of Florida and the southeastern USA and serve as an

important source of feed to the livestock industry. In the state of Florida, the human

population has grown significantly over the past 40 yr, from approximately five million

people in 1960 to approximately sixteen million in 2000 (U.S. Census Bureau, 2002).

This three-fold increase has led to a large increase in urbanization and associated loss of

area devoted to grasslands. Current projections are that population will increase to

twenty-four million by 2030 (Arndorfer, 2003). In the future, producers may be faced

with land constraints and may need to consider intensification of grassland management

as a means of maintaining overall production on a decreasing land resource.

Changes in management intensity could include greater nitrogen (N) fertilization

and stocking rates and use of rotational stocking. These changes have the potential to

affect productivity and profitability of the system; however, some may also increase the

potential for negative environmental impact. Before increasing management intensity

can be recommended, its impact on the environment and on plant and animal

performance must be determined.

The beef industry is a vital component of Florida's large agriculture industry. In

2001 Florida had a total of 975,000 beef cows; this ranks twelfth in the nation and third

for states east of the Mississippi River. Revenues from the beef cattle industry in Florida

totaled 371 million dollars in 2000, accounting for 5.3% of the states total agricultural

cash receipts (Florida Dept. of Agriculture, 2002).









Bahiagrass (Paspalum notatum Fligge) is an essential resource to the beef industry

in Florida. It is the most widely planted grass in the state, covering approximately one

million hectares. Of this area, 90% is grazed by beef cattle (Chambliss, 2000).

Bahiagrass is an aggressive grass that is relatively tolerant of drought and low fertility

soils (Prates et al., 1975). This makes bahiagrass well adapted to the range of

environmental conditions in Florida. The most widely distributed bahiagrass cultivar is

Pensacola, and it is known for its relatively high yields and moderate animal performance

(Chambliss, 2000). Nitrogen is generally the most limiting nutrient for bahiagrass growth

(Gates et al., 2004), and research has shown a potentially large increase in production and

forage N concentration with increasing N rate (Blue, 1988). Thus, there is potential to

achieve greater livestock production on bahiagrass by increasing N fertilization rate.

Stocking method plays an important role in grazing systems. Because of its

grazing tolerance and to minimize cost of production, many bahiagrass pastures in

Florida are continuously stocked during the summer grazing season. Rotational stocking

generally allows for a higher stocking rate and higher gains per unit land area (Blaser,

1986), so potential exists to increase livestock production per hectare on bahiagrass

pastures by using rotational stocking.

Stocking rate is the relationship between number of animals and the area of pasture

to which they are assigned over an extended period of time. Stocking rate is generally

considered to be the most important grazing management decision because it has a major

impact on both forage production and performance of grazing animals (Matches, 1992).

Increasing stocking rate improves the consumption of available herbage per hectare of

grassland, often decreasing individual animal production but increasing animal









production per hectare (Burns et al., 2003). Thus, stocking rate is a powerful tool

influencing production of a given area of grassland.

The thesis research that was conducted was part of a larger project that evaluated

nutrient dynamics and cycling, animal grazing behavior, pasture characteristics, and

animal performance on grazed bahiagrass. The particular areas of focus in the research

reported herein are animal performance and pasture attributes of grazed bahiagrass

pastures managed at different intensities (defined by stocking rate, N fertilizer rate, and

grazing method).

The research was divided into two experiments. The first experiment evaluated

animal performance and forage response of continuously stocked bahiagrass pastures

using three treatments that were defined by stocking rate and N fertilizer rate. Animal

performance was measured as average daily gain of yearling beef heifers and weight gain

per unit land area. Forage responses measured included nutritive value, herbage mass,

herbage allowance, and herbage accumulation. From these data the relationships

between heifer daily gain and bahiagrass herbage mass and bahiagrass herbage allowance

were determined. Results from this study will help to assess the extent to which

increasing management intensity (stocking rate and N fertilization) of bahiagrass pasture

increases pasture and animal performance.

The second experiment evaluated forage responses to four rotational stocking and

one continuous stocking treatment on bahiagrass pasture. The rotational treatments were

defined by length of the grazing period and all had the same rest period. Forage

responses measured include nutritive value, herbage mass, herbage accumulation, and

bahiagrass cover. These data will allow comparison of bahiagrass pasture characteristics









across a wide range of grazing methods and allow conclusions to be drawn about the

potential for increasing bahiagrass pasture performance by changing grazing method.

Data from these experiments are useful from several perspectives. Producers can

use them to make informed management decisions. In addition, this research furthers the

understanding of intensive management and its effect on animal performance and

herbage response. Scientists can use these data to guide future research and to develop

models related to intensified management. In summary, this research is relevant to the

agricultural industry as it explores options for maintaining sustainability in an

increasingly urbanized community, and to the rest of society as it evaluates possible

environmental and economic impacts of management strategies.














CHAPTER 2
LITERATURE REVIEW

Characteristics of Bahiagrass

General

Bahiagrass (Paspalum notatum Fliigge) originated in Brazil and northern Argentina

and was introduced to the southeastern USA in the early 1900s. It has spread extensively

in the southeast and is grown throughout Florida for pasture, turf, and hay (Chambliss,

2000). Bahiagrass is the most widely planted perennial pasture grass in Florida, covering

more than one million hectares (Chambliss, 2000), and is extensively utilized by the

state's beef industry which numbers 975,000 cows (Florida Dept. of Agriculture, 2002).

Bahiagrass is a warm-season, deep-rooted, perennial grass that forms a dense, thick

sod from an extensive root and rhizome system (Burson and Watson, 1995). This

morphology makes it less prone to encroachment from other grasses and weeds.

Bahiagrass is characterized by horizontal stems at the soil surface, and purple leaf sheaths

(Gates et al., 2004). Leaf blades are flat or slightly folded, 3 to 12 cm wide and can grow

from 3 to 30 cm long. Bahiagrass is also characterized by a tall raceme inflorescence

(Gates et al., 2004).

Bahiagrass is aggressive and well acclimated to the variety of environmental

conditions throughout Florida (Prates et al., 1975). It can persist in both well-drained and

low-lying, poorly drained soils. Adapted to the southern USA Coastal Plain region,

bahiagrass performs best in sandy soils with a pH of 5.5 to 6.5 (Twidwell et al., 1998).

Except for highly infertile sites, nutrients needed for adequate growth are limited to N









(Gates et al., 2004). Bahiagrass is also resilient to pressure from most pests. The only

major pest problem is the recent emergence of the mole cricket (Scapteriscus sp.), which

can destroy pasture stands by damaging the root system. Fall armyworms (Spodoptera

frugiperda) can also defoliate stands, but usually only during seasons when more

preferred forages are not available (Burson and Watson, 1995).

Bahiagrass has the C4 photosynthetic metabolism and responds to high temperature

and moisture. 'Pensacola' bahiagrass exhibits little growth under 15C, which limits the

length of its productive period in Florida to April to late October (Mislevy, 1985).

During the spring growing season, bahiagrass is characterized by high nutritive value and

low forage production. This can be attributed to drought and to lower temperatures

which depress plant respiration, preserving nonstructural carbohydrates, and decreased

lignification resulting in greater cell wall digestiblility (Blaser, 1986). During the peak of

the growing season from July to early September, pastures produce higher herbage masss

and digestibility decreases. Performance of animals grazing bahiagrass follows a similar

pattern, with gains being higher in the early growing season, peaking, and then leveling

off or decreasing later in the growing season (Twidwell et al., 1998).

Yield

Forages for production systems should ideally be high yielding and high in

nutritive value to support exceptional animal performance. Pensacola bahiagrass is

highly tolerant of many unfavorable conditions such as overgrazing; however, it is also

known as a low nutritive value forage with lower than average herbage yield among the

adapted warm-season perennial grasses (Sollenberger, 2001). Cuomo et al. (1996)

conducted a study of plant morphology and nutritive value of three bahiagrassses

(Pensacola, 'Argentine,' and 'Tifton 9') as affected by harvest frequency. They found no









differences among cultivars in herbage production, and means were 11.2 Mg ha-1 for

Argentine, 11.9 Mg ha-1 for Pensacola, and 11.8 Mg ha-1 for Tifton 9. Differences were

obvious during the month of May when Argentine produced 1.9 Mg ha-1 as compared to

higher values of 3.1 and 2.9 Mg ha-1 by Pensacola and Tifton 9, respectively. Under high

rates of N fertilizer (450 to 700 kg ha-1), bahiagrass yields up to 15.6, 15.1, and 19.9 Mg

ha-1 have been reported in various states in the southeastern USA (Stanley, 1994; Burton

et al., 1997; Twidwell et al., 1998).

Nutritive Value

Cuomo et al. (1996) found Pensacola to contain a neutral detergent fiber (NDF)

concentration of 657 g kg-1 as compared to 642 g kg-1 for Argentine bahiagrass and 640 g

kg-1 in Tifton 9 bahiagrass over a growing season. In this study acid detergent fiber

(ADF) and lignin were similar for the three grasses, and averaged 323 and 44 g kg-1,

respectively. Muchovej and Mullahey (2000) reported NDF values over a growing

season to be higher; Pensacola NDF was 790 g kg-1, as compared to 783 and 787 g kg-1

for Argentine and Tifton 9, respectively.

The in vitro true digestibility (IVTD) of Pensacola (588 g kg-1) was comparable to

that of Argentine (589 g kg-1) but was lower than Tifton 9 (598 g kg-1) with an N rate of

336 kg ha-1 (Cuomo, 1996). However, Muchovej and Mullahey (2000) found Pensacola

IVTD to be similar to Tifton 9 (510 and 508 g kg-1, respectively) with an N rate of 56 kg

ha-1. Crude protein (CP) of Pensacola and Tifton 9 were identical, 113 g kg-1, but they

were slightly lower than that of the Argentine (118 g kg-1; Cuomo, 1996). Under clipping

management, Muchovej and Mullahey (2000) found no significant differences in

Pensacola CP values over the growing season (average of 96 g kg-1).









Cuomo et al. (1996) also compared NDF and lignin concentrations of different

plant parts (leaf, stem, and whole plant) for the three bahiagrass cultivars over the entire

growing season. They found stem, leaf, and whole-plant NDF to be higher in Pensacola

(646, 701, and 660 g kg-1, respectively) than Tifton 9 (636, 669, and 640 g kg-1). Lignin

was also slightly higher in Pensacola than Tifton 9 (40, 59, 44 g kg-1 versus 37, 54, and

41 g kg1-, respectively).

Nutritive value of grazed bahiagrass declines over the growing season due to high

temperature and accumulation of mature material and reproductive structures. Utley et

al. (1974) reported IVOMD of 679 g kg-1 for bahiagrass clipped in May compared to 429

g kg-1 in late September. Cuomo also found a decrease in in vitro organic matter

digestibility (IVOMD) across the season with values of 629 g kg-1 in late May and 562 g

kg-1 in early September at 20-d harvests intervals. Crude protein decreased from 139 to

110 g kg-1 over the same period, while NDF, ADF, and lignin increased from late May to

early September (629 to 657, 302 to 328, and 38 to 47 g kg-1, respectively).

Animal Performance

In livestock operations, animal performance is the essential goal. Bahiagrass is

known to withstand heavy grazing and poor growing environments; however, it is also

known for its average to lower than average animal performance. This is particularly a

problem in Florida during hot summer months when cattle are under stress and

sometimes have negative average daily gains (ADG). In a study by Prates et al. (1975)

ADG was measured monthly on continuously stocked Pensacola bahiagrass from May

through October. This study utilized the put and take system to adjust stocking rate, and

fertilizer was applied at 193 kg ha-1 yr- of elemental N. They reported ADG to be 1.00

kg d-1 in May; however, ADG steadily declined to -0.52 kg d-1 in September with only a









slight increase to 0.15 kg d-1 in October. Also in this study, gain ha-1 was measured in

each month. In May, cattle gained 122 kg ha-1. They lost 97 kg ha-1 in September, and

gained 10 kg ha-1 in October. Twidwell et al. (1998) reported ADG of steers grazing

Pensacola bahiagrass pastures to be 0.43 kg compared to 0.49 kg for steers grazing

'Coastal' bermudagrass [Cynodon dactylon (L.)] over a 4-yr grazing trial. Additional

animal performance data will be discussed later in the literature review as it relates to

specific management practices.

Nitrogen Fertilization

Cool-Season and Native Grasses

Research has shown that C3 grasses have the potential to respond to N application.

Tall fescue (Festuca arundinacea Schreb.) is grown in many areas of the temperate USA.

Moyer et al. (1995) evaluated forage production and N concentration of fescue at three N

application rates: 13, 112, and 168 kg ha-1. As N rates increased, forage DM production

increased from 3.26 to 4.11 to 4.49 Mg ha-1, respectively. At these N rates, forage CP

concentrations were 140, 176, and 194 g kg-1, respectively, showing a significant increase

as N rate increased. Zhang et al. (1995) evaluated annual ryegrass (Lolium multiflorum

L.) N and N constituents. In this study, total N increased from 29.8 to 50.4 g kg -1 as N

application increased from 0 to 224 g kg-1. Also it was reported that as N fertilization

increased, ADF-bound N, as a constituent of total N, decreased from 7.63 to 3.41 g kg 1

From this it is concluded that increasing N application can decrease ADF-bound N in

addition to increasing N concentration in forages.

Texas bluegrass (Poa arachnifera Torr.) is a cool-season perennial grass used for

pasture in the southern Great Plains. Pitman et al. (2000) evaluated the response of









bluegrass to N fertilization rates of 0 and 100 kg N ha-1. At these levels, forage yields

across 2 yr were 1.8 and 4.1 Mg ha-1, respectively.

Native range grasses also are an important part of many forage production systems.

Lorenz and Rogler (1972) evaluated response of a mixture of prairie vegetation to four N

fertilization rates across an 8-yr study. Among the species tested were western

wheatgrass (Agropyron smithii Rydb.), blue grama (Bouteloua gracilis [H.B.H.] Lag.),

threadleaf sedge (Carexfilifolia, Nutt.), and needle-and-thread (Stipa comata Trin. &

Rupr.). At N rates of 0, 45, 90, and 180 kg ha-1, forage DM production was 0.8, 1.9, 3.0,

and 3.1 Mg ha-l, respectively. Nichols et al. (1990) also evaluated the response of

smooth bromegrass (Bromus inermis Leyss.), redtop (Agrostis stolonifera L.), timothy

(Phleum pratense L.), slender wheatgrass [Agropyron trachycaulum (Link) Malte],

quackgrass [A. repens (L.) Beauv.], Kentucky bluegrass (Poapratensis L.), prairie

cordgrass (Spartinapectinata Link) and several sedges (Carex spp. L) and rushes (Juncus

spp. L.) to N application over a 4-yr trial. Nitrogen was applied at rates of 0, 45, 90, and

135 kg ha1. At these levels, forage DM production was 6.1, 6.9, 8.1, and 8.7 Mg ha-1,

respectively. This study also reported the nutritive value response to increasing N rates.

Across the treatments, there were no significant differences in either CP or IVDMD.

Barley (Hordeum vulgare L.), a cool-season annual grass, can serve as an important

alternative feed crop in the southeastern USA (DiRienzo et al., 1991). DiRienzo et al.

(1991) evaluated barley yield responses to spring N applications across 2 yr. At N rates

of 0, 45, 90, and 135 kg ha-1 forage DM yields were 9.6, 10.5, 11.0, and 11.5 Mg ha-1,

respectively. Barley showed higher DM yields, however, response to N decreased as N









rate increased having an initial response of 20 kg forage kg-1 N, but decreasing to 13 kg

forage kg-1 N at the highest fertilization rate.

Tropical Grasses

Tropical C4 grasses are used throughout the southern USA. Because of the

growing environment, these grasses account for a large proportion of the nutrients in

many ruminant animal diets in this region. These grasses also have the potential for

response to N application.

Bermudagrass is a C4 grass used widely throughout the southeastern USA as a

forage for livestock. Thom et al. (1990) evaluated 'Tifton 44' bermudagrass yield and

nutritive value responses to N fertilization over a 5-yr period. At N rates of 0, 135, 270,

405, and 540 kg ha-1, forage DM yields were 2.5, 9.1, 15.8, 16.6, and 16.0 Mg ha-1,

respectively. Bermudagrass DM yield responded up to the 405 kg ha-1 rate, but yield

decreased at 540 kg ha-1. Looking at nutritive value, N application did not significantly

increase the IVDMD of the bermudagrass; all treatments averaged approximately 600 g

kg 1. Wiendenfeld (1988) evaluated Costal bermudagrass and 'Renner' lovegrass

[Eragrostis curvula (Schard.) Ness] response to N fertilization. In this study N was

applied at 0, 112, and 224 kg ha-1. At these treatment levels, bermudagrass increased

yield per unit N with increasing N rates. These responses suggest that bermudagrass

could possibly have made efficient use of N above those applied in this study. In a study

by Prine and Burton (1956), the effect of N rate was evaluated on yield and CP

concentration of Coastal bermudagrass. At N levels of 0, 112, 336, 672, and 1008 kg ha-1

hay DM yields were 4.9, 7.5, 13.5, 17.2, and 18.4 Mg ha-1, respectively. Bermudagrass

showed the highest increase in production (kg forage/kg N ha-1) at the 336 kg ha-1 rate

and then showed a smaller response above this level. The forage CP concentrations were









97, 113, 150, 170, and 190 g kg-1. Similar to yield, the greatest response to N was at 336

kg ha-1, and response leveled off at higher N rates.

Limpograss [Hemarthria altissima (Poir) Stapf & C.E. Hubb] is another C4 grass

that serves an important role in the livestock industry in Florida. Limpograss is also

known for its seasonally low N concentrations (Lima et al., 1999) and has the potential

for a response to applied N. Christiansen et al. (1988) compared the response of three

cultivars of limpograss to three N fertilization rates (0, 120, and 480 kg ha-1) and several

defoliation intervals. At a defoliation interval of 3 wk, 'Floralta' limpograss responded to

these N rates with DM yields of 2.7, 4.4, and 6.8 Mg ha-1, respectively. Both CP and

IVOMD increased in response to N rate and were 75, 90, and 97 g kg-', and 499, 507, and

518 g kg- respectively. Lima et al. (1999) compared limpograss atN rates of 50 and

150 kg ha-1. Increasing the N rate resulted in an increase in carrying capacity of

approximately 100 heifer days ha-1 in the year when rainfall was near normal, and

carrying capacity was increased by 37 heifer days ha-1 in a drier than normal year (58%

of the 70-yr average rainfall). Forage DM production increased to support the increase in

carrying capacity. Increasing the N rate also increased CP and IVOMD of the blade,

sheath, and stem portions of the plant. Velez-Santiago and Arroyo-Aguilu (1983)

measured limpograss production and nutritive value at several fertilization rates. At rates

of 224, 448, and 896 kg ha-1, DM production of 'Bigalta' was 2.7, 3.5, and 4.4 Mg ha-1,

respectively. At these N rates, CP concentrations also increased at a harvest interval of

30 d and were 94, 106, and 119 g kg-1. From these data it is apparent that limpograss has

the potential to increase DM production and CP up to high levels of N application.

Limpograss also shows an IVOMD response to N unlike many other tropical grasses.









Other tropical grasses respond to N fertilization in terms of DM production and CP

concentration. Faria et al. (1999) evaluated the nutritive value of 'Mott' dwarf

elephantgrass (Pennisetumpurpureum Schum.) in response to N fertilization. At N rates

of 0, 150, 300, and 450 kg ha-1, CP ranged from 80 to 83 g kg-1 and was not different

among treatments. The IVDMD ranged from 600 to 620 g kg-1; these values were also

not significantly different.

Springer and Taliaferro (2001) evaluated N fertilization of buffalograss [Buchloe

dactyloides (Nutt.) Engelm] across a range from 0 to 134 kg ha-1. At these levels, forage

DM production significantly increased from approximately 1.8 to 2.7 Mg ha-1. The N

rate also had a significant effect on CP, increasing it from 90 to 124 g kg-1; however,

there was no significant effect on IVDMD.

In a study by George et al. (1990), forage production and nutritive value of

switchgrass (Panicum virgatum L.) were compared at two N levels, 0 and 90 kg ha-1.

There was an increase in DM production from 1100 to 1800 kg ha-1 with N application.

Also there was a significant increase in CP and IVDMD, with CP increasing from 120 to

160 g kg-1 and IVOMD from 670 to 700 g kg-1, respectively.

Tyagi and Singh (1986) reported the effect of N application on forage production

and nutritive value in dinanathgrass (Pennisetum pedicellatum Trin), a tropical grass

native to Africa and India. In this study, N was applied at rates ranging from 0 to 160 kg

ha-l. Forage DM productions increased from 9.1 to 20 Mg ha-1 with increasing N, but

production did not increase above 120 kg ha-1. Forage CP significantly increased from

59 to 91 g kg-1 as N application increased from 0 to 160 kg ha-1, and digestibility

increased from 606 to 658 g kg-1 over the same range of N rates.









These data suggest that N fertilization increases grass production and CP

concentration across a wide range of grass species and N rates. Nitrogen effects on other

measures of forage nutritive value are less consistent. The next section of the review

focuses on bahiagrass response to N fertilization.

Bahiagrass

Nitrogen is generally the most limiting nutrient for bahiagrass (Gates et al., 2004).

In Florida's sandy soils, soil nutrient retention capacity is minimal due to their coarse

texture and low organic matter concentration. Significant amounts of fertilizer are

required in order for pastures to produce high production of forage and animal product.

Blue (1988) conducted an experiment that evaluated Pensacola bahiagrass

response to three rates of N application applied using five different schedules of

application. He found that application date did not have a significant effect on total

annual DM production; however, there was a large increase in production and forage N

concentration with increasing N rate. Twidwell et al. (1998) reported that an increase in

N rate from 0 to 445 kg ha-1 increased total DM production from 4.0 to 15.6 Mg ha-1 (3.9-

fold yield increase). Burton et al. (1997) reported that increasing N rate from 56 to 448

kg ha-1 on Pensacola bahiagrass increased production from 6.0 to 15.1 Mg ha-1. Stanley

(1994) applied N to Tifton 9 bahiagrass at rates of 0, 84, 168, 336, and 672 kg ha-1. In

this study, he found DM productions of 7.4, 8.7, 10.9, 15.5, and 19.9 Mg ha-1,

respectively. Forage production per unit N applied increased up to 336 kg ha-1 (24.1 kg

forage/kg N ha-1), and decreased thereafter (18.6 kg forage/kg N ha-1 at 672 kg ha-1).

Ruelke and Prine (1971) evaluated Pensacola bahiagrass along with seven other grasses

at three fertility levels, 134, 269, and 538 kg N ha-1. Across 4 yr, the bahiagrass DM









response to N was 6.7, 9.0, and 11.7 Mg ha-1. These data indicate that bahiagrass

production can increase dramatically in response to increasing N fertilization.

The potential for N fertilization to increase forage CP and change cell composition

has been explored in previous studies. Twidwell et al. (1998) reported that an increase in

N rate from 0 to 445 kg ha-1 increased total herbage CP from 105 to 144 g kg-',

respectively. Burton et al. (1997) reported that increasing N rate from 56 to 448 kg ha-1

on Pensacola bahiagrass increased forage N concentration from 11 to 17 g kg-1. Blue

(1988) reported 2-yr average forage N concentrations of 35, 115, and 204 kg ha-1 for N

applications of 0, 100, and 200 kg ha-1, respectively. Stanley et al. (1977) evaluated cell

wall constituents across N rates of 0, 84, 168, and 336 kg ha-l. This study found no

significant difference in cell wall composition across fertilization rates.

From recent literature for bahiagrass, it is apparent that there is potential to increase

production of bahiagrass in response to N fertilization. Also there is evidence of

increased CP concentration as a result of N fertilization; however, the response of

IVOMD is not consistent.

Environmental Implications

From the reviewed literature, it is evident that N fertilization increases grass yield

and crude protein, and in turn, has the potential to increase animal production. However,

increasing N rates will reach a point where there are diminishing returns to forage

production and possibly significant N losses to the environment. The sandy, low organic

matter soils in Florida have limited ability to retain N. Therefore, regulatory agencies are

concerned with the potential of surface and ground water contamination from excessive

N applications on agricultural land (Muchovej and Rechcigl, 1994). With increased

stocking rates, there is also potential of increased nutrient loading from animal waste.









Runoff and leaching of nutrients from animal waste may contaminated water supplies

(Hammond, 1994). Proper management of animals and resources under increased

management intensity is required to avoid these potentially harmful environmental

impacts.

Grazing Management

Grazing management involves a series of choices that determine the nature of the

plant-animal interaction on pasture. Primary choices include those of grazing method,

grazing frequency, and grazing intensity. These will be discussed in the section that

follows.

Grazing Method

Stocking method plays an important role in a grazing system. There are two

general stocking methods utilized, rotational and continuous stocking. Rotational

stocking consists of subdividing pastures into paddocks that have periods of both grazing

and rest. This method generally allows for a higher stocking rate than continuous

stocking (Blaser, 1986). In contrast, continuous stocking allows constant access to all

areas of the pasture. At moderate stocking rates this method often results in greater gain

per animal, associated with increased opportunity for diet selection, however, gain per

unit land area may be less than with rotational stocking because of lower stocking rate

(Blaser, 1986).

Sollenberger et al. (1988) compared animal performance of Pensacola bahiagrass

and Floralta limpograss on continuously stocked pastures. Pastures were fertilized at a N

rate of 200 and 180 kg N ha-1 during a 2-yr study. A variable stocking rate was used and

average stocking rates were 5.4 and 5.2 animals ha-1 for limpograss and bahiagrass,

respectively (based on 320-kg animals). Cattle on bahiagrass had ADG of 0.38 kg d-1









across the two grazing seasons, compared to 0.33 kg d-1 on limpograss. These authors

pointed out that the lack of difference in ADG between forages might be associated with

the low CP concentration of limpograss, even though limpograss IVOMD was higher

than bahiagrass (539 and 484 g kg-1, respectively). Also in mid- to late summer,

limpograss pastures had an accumulation of stem material that may have limited

voluntary intake.

Sollenberger et al. (1989) also compared animal performance on rotationally

stocked Floralta limpograss and Pensacola bahiagrass pastures across three grazing

seasons. The N rate for this study averaged 180 kg ha-1 yr-1. The ADG of animals

grazing bahiagrass remained the same as that observed under continuous stocking and

averaged 0.38. Cattle gains on limpograss were 0.41 kg d-1 and not different than those

on bahiagrass. Average stocking rates of bahiagrass pastures under rotational stocking

were 5.3 animals ha-1 compared to 6.7 animals ha-1 on limpograss.

Williams and Hammond (1999) compared rotational and continuous intensive

stocking of cattle on bahiagrass pastures. Cattle weight gains did not differ over the 3-yr

trial. Forage IVOMD and CP were similar between rotational and continuous stocking.

Hammond et al. (1997) also compared rotational stocking and continuous stocking as it

affected animal performance of Angus cattle. This study found no difference in ADG

among methods (0.68 kg d-1 for rotational and 0.67 kg d-1 for continuous).

Mathews et al. (1994) compared Holstein heifer and 'Callie' bermudagrass pasture

response to rotational and continuous stocking over a 2-yr period. In this study,

treatments were defined as rotational stocking (15 paddocks) with short grazing periods

(1.5 to 2.5 d paddock-') (RS-SG), rotational stocking (3 paddocks) with long grazing









periods (10 to 14 d paddock-') (RS-LG), and continuous stocking (CS). The study found

no difference in season-long ADG for the rotational treatments in both years. During the

first year, ADG on CS was significantly higher than either of the RS treatments; however

there were no differences among treatments in the second year. Comparing average

stocking rate among treatments showed that RS-SG was greater than RS-LG and CS

during the first year (3920, 3200, and 3230 kg liveweight ha-1 d-1, respectively), and there

were trends toward a similar response during the second year. The IVOMD values were

not different across treatments during the first year; however, in the second year the RS-

LG treatment was significantly higher than the CS, 574 and 558 g kg-1, respectively.

There were no significant differences among CP values across treatments. The authors

concluded that effect of grazing method on heifer performance was slight, but potential

exists for long-term differences because Callie persistence was greater under rotational

stocking.

Tharel (1989) compared rotational and continuous stocking of three bermudagrass

cultivars (Common, Tifton 44, and Midland). Both continuously and rotationally stocked

pastures were 1 ha in size, and the rotational pastures were subdivided into 10, 0.1-ha

paddocks. Average daily gains across cultivars were higher for continuous compared to

rotational stocking, 0.7 and 0.6 kg d-1, respectively. On a gain per hectare basis,

rotationally stocked pastures outperformed continuous, 730 and 600 kg ha-l, respectively.

Grazing Frequency

Data indicate a potential for increasing DM production with increasing intervals

between grazing (decreasing grazing frequency; Mislevy and Brown (1991). Frequent

removal of forage may decrease non-structural carbohydrate reserves, decreasing the

plants ability to produce DM; however, as interval between grazings increases, CP and









IVOMD decrease. Frequent grazing prevents plants from reaching maturity, thus

increasing the proportion of young, lush herbage.

Mislevy and Brown (1991) evaluated bahiagrass at four grazing frequencies, 2, 3,

5, and 7 wk across 3 yr. As interval between grazing increased, DM production increased

from 7.1 to 10.8 Mg ha-1 yrf1. The grazing frequency effect on IVOMD was less in early

season, but in mid-summer IVOMD decreased from 540 g kg-1 at 2 wk to 480 g kg-1 at 7

wk. The CP decreased with increasing interval between grazing in June (140 to 80 g

kg-1) and in mid-summer (110 to 70 g kg-1 at 2 and 7 wk, respectively). Gates et al.

(1999) evaluated bahiagrass at three cutting intervals, 2, 4, and 8 wk, during three

growing seasons. With the exception of the 8-wk interval in Year 2, DM production

increased as cutting interval increased. There was no change in IVDMD among cutting

intervals, but there was a slight decreasing trend as interval increased. Cuomo et al.

(1996) compared three grazing frequencies, 20, 30, and 40 d, of bahiagrass across two

growing seasons. At these frequencies, total forage dry matter production was 10.6, 11.8,

and 12.3 Mg ha-1, respectively. Herbage CP was significantly higher at the 20-d grazing

frequency (124 g kg-1), but it was equal for the 30 and 40-d intervals (110 g kg-1). In

vitro true digestibility did not significantly change across grazing frequencies. Beaty et

al. (1970) evaluated bahiagrass across six harvest frequencies, 1, 2, 3, 4, 5, and 6 wk. At

these frequencies, average DM productions for the 2 yr study were 3.5, 3.4, 3.0, 2.7, 3.8,

and 2.6 Mg ha-1, respectively, showing little effect of clipping frequency. Stanley (1994)

compared bahiagrass at harvest intervals of 1, 2, 4, 8, and 16 wk, with a N rate of 336 kg

ha-1. Forage DM production was highest for the 8-wk interval (18.9 Mg ha-1). Relative

production for the remaining harvest intervals (with DM productions of the 8-wk









treatment assigned a value of 1.00) were 0.36, 0.53, 0.81, and 0.75 for the 1, 2, 4, and 16-

wk treatments, respectively; illustrating an increase in forage production as harvest

interval increases to 8-wk, but no further increase with delayed harvest.

Adjei et al. (1989) compared bahiagrass, limpograss, and bermudagrass at four

grazing frequencies (2, 4, 6, and 8 wk) for two growing seasons. At these grazing

frequencies, Pensacola bahiagrass did not show a significant increase in DM production

with longer intervals between grazing. 'Hemarthria 869' limpograss and 'Tifton 79'

bermudagrass both showed a linear increase in DM production from the 2 to 8 wk

interval, 1.8 to 5.6 Mg ha-1 and 4.3 to 7.8 Mg ha-1, respectively. There were linear and

quadratic decreases in bahiagrass CP (130 to 73 g kg-1) as interval increased from 2 to 8

wk. Limpograss and bermudagrass CP also declined markedly with increasing interval,

107 to 57 g kg-1 and 160 to 65 g kg-1, respectively. Bahiagrass IVOMD decreased

linearly with increasing interval between grazing (560 to 460 g kg-1). Limpograss did not

show a significant change in IVOMD, but bermudagrass IVOMD decreased linearly from

610 to 470 g kg-1. This study also evaluated forage persistence at these grazing

frequencies. Over all grass entries, there was a significant linear decrease in common

bermudagrass invasion, from 51% to 36%, as interval between grazing increased.

These data suggest that production responses of bahiagrass to defoliation frequency

are likely smaller than those of more upright-growing grasses. This is probably due to

the ability of bahiagrass to maintain leaf area even under frequent, close grazing and to

self shading as regrowth interval increases.

Grazing Intensity

In a forage system, grazing intensity is an important means by which both animal

and forage production can be manipulated. It is important to maximize forage utilization,









but at the same time maintain a vigorous pasture stand. Grazing intensity can be

characterized in a number of ways including grazing height and stocking rate.

Stocking rate is defined as the relationship between the number or weight of

animals and the area of pasture which is available for grazing over an extended period of

time. Stocking rate has a major influence on forage production and animal performance,

thus, it is considered to be the most significant grazing management decision (Matches,

1992). Increasing stocking rate increases the removal of available forage per unit land

area; however, nutritive value or available forage may decrease as grazing height

decreases. This reduction in quantity and or quality causes consumed energy to be

reallocated from maximum daily animal growth to meeting the maintenance requirement

(Burns et al., 2003), thus reducing production per animal. Conversely, increasing the

stocking rate of an underutilized pasture causes an increase in animal production per unit

land area up to a point (Mott and Lucas, 1952). Exceeding this point causes a decrease in

production per unit land area due to the decline in forage availability and daily animal

production; the latter occurs because a greater proportion of total forage intake is devoted

to meeting the maintenance requirement of the animal. Consequently, stocking rate is an

important factor influencing production of a given pasture.

Adjei et al. (1980) evaluated pasture and animal response of three stargrass

cultivars to three stocking rates (SR): 7.5, 10, and 15 cattle ha-1 (cattle = 250 kg avg.

liveweight). Across 2 yr, forage DM production increased from 17.0 to 20.1 t ha-1, as SR

increased from 7.5 to 15 cattle ha-l. For UF-5 stargrass, IVOMD and CP increased as

SR increased (460, 488, and 523 g kg-land 87, 102, and 111 g kg-1, respectively).

Average daily gain (ADG) of cattle on UF-5 decreased as stocking rate increased (0.46,









0.37, and 0.24 kg d-1). Gain per unit land area increased from the 7.5 to 10.0 SR (570 to

610 kg ha-1, respectively), but decreased to 590 kg ha-1, as SR increased to 15 cattle ha-1.

Conrad et al. (1981) compared performance of beef steers on two cultivars and three

experimental hybrids of bermudagrass at four SR. Average SR across grasses were 4.6,

6.8, 8.8, and 9.0 head ha-1. With increasing SR, ADG decreased (0.83, 0.70, 0.48, and

0.38 kg head-1 d-1, respectively). Animal performance on a per unit land area basis

increased from 581 to 738 kg ha-1 as SR increased from 4.6 to 6.8 head ha-1, but then

decreased as SR increased to 8.8 and 9.0 head ha-1 (651 and 641 kg ha-1, respectively).

Even though there are a lack of data related to stocking rate of bahiagrass pastures,

from the data presented for other grasses, it appears likely that stocking rate will affect

both forage and animal responses significantly.

Summary

Bahiagrass serves as an important feedstuff to the beef cattle industry in the

Southeastern USA. Bahiagrass response to N fertilization is well documented in the

literature, but the effects of grazing method and grazing intensity on pasture and animal

responses have received less attention from researchers in the region. Research assessing

the effects of management intensity, defined as combinations of N rate, stocking rate, and

grazing method, on productivity of bahiagrass-livestock systems is thus deemed

important for the future of these systems in Florida and the Southeast. The research that

follows includes two experiments that address these issues.














CHAPTER 3
HERBAGE AND ANIMAL PERFORMANCE RESPONSES TO MANAGEMENT
INTENSITY OF CONTINUOUSLY STOCKED BAHIAGRASS PASTURES

Introduction

'Pensacola' bahiagrass (Paspalum notatum Flugge) is widely adapted in Florida

and the Gulf Coast; however, it is lower in nutritive value and yield than many warm-

season perennial grasses (Sollenberger, 2001). Consequently, performance per animal

and per unit land area on bahiagrass pastures are often below levels typically observed for

other planted C4 grasses. Despite these limitations, bahiagrass tolerates close grazing and

a wide range of soil conditions, and it is relatively easy to establish and resistant to weed

encroachment. Due to these advantages, bahiagrass covers more area (1 million hectares)

than any other planted grass in Florida (Chambliss, 2000). Approximately 80% of all

planted grasslands in Florida are seeded to bahiagrass, and more than 90% of bahiagrass

pastures are used for grazing by beef cattle.

Over the past 40 yr, the population of Florida has grown from approximately five

million to 16 million and is projected to reach 24 million by the year 2030 (Arndorfer,

2003). Given this scenario, it is likely that land area available for agricultural uses will

decrease further, and producers may face the task of maintaining economic livelihood on

less land. A possible solution to this problem is to increase management intensity to

achieve equal or higher gains on smaller amounts of land. Management intensity within

the context of bahiagrass-based grassland systems includes N fertilizer rate, animal

stocking rate, and grazing management. Currently there is little information in the









literature regarding the effect of increasing N fertilizer rate and stocking rate on

performance of animals grazing bahiagrass pasture.

Nitrogen is generally the most limiting nutrient for bahiagrass swards (Gates et al.,

2004), and N fertilization has the potential to increase both herbage accumulation and

crude protein (CP) concentration (Blue, 1988; Burton et al., 1997; Twidwell et al., 1998).

With increased herbage accumulation, stocking rate can be increased to utilize the

additional herbage while potentially maintaining the same rate of daily live weight gain.

Should this occur, the result would be an increase in gain per unit land area on N

fertilized bahiagrass pastures.

Therefore research was conducted to evaluate the effect of a range of management

intensities of continuously stocked bahiagrass pastures on performance of yearling beef

heifers. Treatments were chosen to encompass and exceed the range in management

intensity used by current producers. The specific objectives of this study were to

evaluate the effects of combinations of N fertilizer rate and stocking rate of bahiagrass

pastures on herbage mass, accumulation, and nutritive value, and yearling beef heifer

daily gain and gain per hectare.

Methods and Materials

Experimental Site

This experiment was conducted at the Beef Research Unit, located northeast of

Gainesville, FL (290 43' N lat.). Pastures used were well-established swards of Pensacola

bahiagrass that had been stocked rotationally at similar stocking rates (1.5 animal units

[AU, one AU=500 kg live weight] ha-) during the previous five summer grazing seasons.

Soils at the site were predominantly of the Pomona and Smyrna series of sandy Spodisols









with average pH of 5.9. Soil P, K, Ca, and Mg concentrations were 5.3, 28, 553, and 98

mg kg-', respectively.

Treatments and Design

For the purposes of this experiment, management intensity was defined as a

combination of a N fertilizer rate and an animal stocking rate. The three management

intensity treatments were LOW (40 kg N ha-1 yr-, 1.2 AU ha-1 stocking rate),

MODERATE (120 kg N ha-1 yr-, 2.4 AU ha1 stocking rate), and HIGH (360 kg N ha-1

yr-i, 3.6 AU ha-1 stocking rate), and treatments were arranged in two replicates of a

randomized block design. Pasture sizes were varied to achieve the treatment stocking

rates and were 1, 0.5, and 0.33 ha for the LOW, MODERATE, and HIGH treatments,

respectively. The target stocking rates were chosen based on the projection that heifers

with an average initial weight of 270 to 275 kg would be assigned to all treatments and

would gain 0.35 kg d-1 (based on Sollenberger et al., 1989) over a 160-d trial to achieve a

final weight of 325 to 330 kg. This would result in an average weight of approximately

300 kg during the grazing season and an average stocking rate appropriate for that

treatment. Because heifer live weights were greater than expected at the start of grazing

each year, actual SR was greater than our target and is reported in Table 3-1.

The range of treatments was selected to bound those used by most beef cow-calf

producers in Florida. The LOW treatment approximates the current industry average,

while MODERATE represents the most intensive of current management practices. The

HIGH treatment represents a considerable increase in management intensity from any

current management, but one that is within reason should land limitations to cattle

production become severe. The choices of N rate and stocking rate for HIGH were based

on data from Burton (1997) and Twidwell et al. (1998) who found that bahiagrass forage









production was approximately three times greater for N rates near the highest compared

to the lowest used in the current study, thus keeping forage mass and stocking rate nearly

in balance across these treatments.


Table 3-1. List of actual stocking rates (SR) of continuously stocked bahiagrass pastures.



Target Actual SR (AUt ha-1)
SR
(AUt ha-1) 2001 2002

1.2 1.5 1.4

2.4 3.0 2.8

3.6 4.4 4.1
SAU = 500 kg live weight


Pasture and Animal Management

Bahiagrass pastures were continuously stocked during the growing seasons of 2001

(112 d) and 2002 (168 d). Grazing was initiated in the spring or early summer of each

year when adequate forage was available to support the livestock (26 June 2001 and 22

May 2002). Grazing was delayed in 2001 because of April and May drought (Table 3-2).

The LOW and MODERATE treatment pastures received 40 kg N ha-1 when temperature

and soil moisture conditions favored a response to N (June 2001 and April 2002). It is

typical for all N to be applied to grazed bahiagrass during spring by Florida beef

producers because forage is in short supply and the breeding season is underway. The

MODERATE pastures received two additional applications of 40 kg N ha-l, one in mid-

July, and the other in mid-August. The HIGH pastures received four applications of 90

kg N ha-1 in 2002, in late April/early May, mid-June, mid-July, and mid-August.









Because the grazing season was shorter than normal in 2001, the HIGH treatment only

received 270 instead of 360 kg N ha-1 yr1. Actual N fertilization dates for both years are

reported in Table 3-3. Phosphorus (17 kg ha-) and K (66 kg ha-) were applied to all

treatments prior to N application in 2001 (17 April) and at the first N application in 2002

(30 April). MODERATE and HIGH treatments received a second application of the

same rates on 15 July 2002.


Table 3-2. Rainfall at the experiment site for years 2001-2002 and the 30-yr average for
Gainesville, FL.


Rainfall (mm)


2001
Departure
From normal
-71
-74
71
-47
-85
8
68
-132
40
-50
-31
-31


Actual
99
25
50
62
33
135
249
165
133
63
95
128


2002
Departure
From normal
15
-74
-43
-12
-73
-34
69
-38
-10
4
43
47


Two crossbred (Angus X Brahman) yearling beef heifers of average 344 and 313

kg liveweight were assigned to each pasture in 2001 and 2002, respectively. No other

animals were added to the pasture throughout the course of the grazing season. Cattle


Month
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct

Nov
Dec


30-yr
Average
83
99
93
75
106
168
180
203
142
59
52
81


Actual
12
25
164
28
22
176
248
71
183
9
20
50









were provided free-choice access to water and a trace mineral mix (Table 3-4). Artificial

shade (3.1 x 3.1 m) was available on all treatments.


Table 3-3. Nitrogen application dates on continuously stocked bahiagrass pastures.

N application dates (rates in kg ha-1)
Treatment 2001 2002

Low 13 June (40) 30 Apr (40)


Moderate 13 June (40) 30 Apr (40)
20 July (40) 15 July (40)
24 Aug (40) 20 Aug (40)


High 13 June (90) 30 Apr (40)
20 July (90) 14 May (50)
24 Aug (90) 12 June (90)
15 July (90)
20 Aug (90)


Table 3-4. Composition of mineral supplement.

Mineral g kg-
Ca 200 -230
P >60
Na 230 250
Fe >10
F <0.6
Co >0.0005
Cu >0.005
I >0.0005
Mn >0.02
Se >0.00012
Zn >0.04









Pasture Responses

Pastures were sampled just prior to initiation of grazing and every 14 d thereafter

during the grazing season. Herbage mass, herbage accumulation, and herbage nutritive

value (CP and in vitro digestibility) were measured. Double sampling was used to

determine herbage mass. Double sampling refers to a technique that includes both a

direct and indirect measure of the response of interest. In this case the indirect measure

was settling height of a 0.25-m2 aluminum disk, and the direct measure was hand clipping

of all herbage from 2 cm above soil level to the top of the canopy. At each sampling date,

30 disk heights were taken in each pasture. Sites were chosen by walking a fixed number

of steps between drops of the disk and all sections of the pasture were represented. Every

28 d, 20 double samples were taken, approximately three to four in each of the six

experimental pastures. Sites were chosen that represented the range of herbage mass

present on the pastures. At each site the disk height was measured and the forage

clipped. Clipped forage was dried for 48 h and weighed. Actual herbage mass was

regressed on disk height to develop a calibration equation. This equation from the double

samples was used to predict pasture herbage mass using the average disk height (from the

30 disk heights) for each pasture. Regression equations are presented in Table 3-5.

Because cattle were resident on these pastures at all times, a cage technique was

used to measure herbage accumulation. Six 1-m2 cages were used per pasture. The cages

were placed in the pasture at the initial sampling date. Sites were chosen that had a disk

settling height that was approximately the same (1cm) as that of the average on that

pasture. Disk settling height was recorded at a specific site and the cage placed. After 14

d, the cage was removed and the new disk settling height recorded. Herbage

accumulation was calculated as the change in herbage mass during the 14 d that the cage









was present. At the end of each 14-d period, cages were moved to new locations on the

pasture that approximated the average disk settling height for the pasture.

Table 3-5. Herbage mass double sample regression equations.

2001 2002

Date Equation R2 Date Equation R2

11 July y = 220 97 0.82 22 May y = 235x 313 0.86

8 Aug. y = 251x 250 0.84 19 June y = 260x 331 0.75

4 Sept. y = 337x 401 0.85 14 July y = 336x 724 0.78

2 Oct. y = 279x + 359 0.80 14 Aug. y = 328x 648 0.83

11 Sept. y = 299x 277 0.81

9 Oct. y = 357x 447 0.82




Forage allowance is defined as herbage mass per unit of animal liveweight. Forage

allowance was calculated for each pasture during each 28-d period as the average herbage

mass (mean across three sampling dates in that 28-d period) divided by the average total

liveweight during that period.

Herbage CP and in vitro organic matter digestibility (IVOMD) were used as

measures of nutritive value. At initiation of grazing and every 14 d thereafter, hand-

plucked samples were taken from each pasture. This technique attempts to represent the

diet consumed by the grazing animal by removing only the top 5 cm of herbage at

approximately 30 locations across each pasture. The herbage was dried at 600C and

ground to pass a 1-mm screen. Analyses were conducted at the Forage Evaluation









Support Laboratory using the micro-Kjeldahl technique for N (Gallaher et al., 1975) and

the two-stage technique for IVOMD (Moore and Mott, 1974).

Bahiagrass cover was estimated visually at the beginning of the 2001 grazing

season and the end of the 2002 grazing season. Five equally spaced line transects were

established for each paddock. Percent bahiagrass was estimated at eight locations along

each transect for a total of 40 observations per paddock. Data reported are changes in

bahiagrass cover between those two dates.

When pasture data are reported as total-season averages, the data are the averages

of all of the 14-d sampling interval data across the season. When reported as 28-d period

averages, the data are the average of the three sampling dates within each 28-d period

(Days 0, 14, and 28).

Animal Responses

Cattle were weighed at initiation of the experiment and every 28 d thereafter.

Weights were taken at 0800 h following a 16-h feed and water fast. Average daily gain

was calculated for each 28-d period and for the entire grazing season. Weight gain per

hectare was calculated for each pasture over the entire grazing season.

Statistical Analysis

Data representing annual totals or averages (e.g., total herbage accumulation,

average pasture herbage mass, average herbage accumulation rate, average herbage

allowance, average CP and IVOMD, and average daily gain, gain per hectare) were

analyzed using analysis of variance in PROC GLM of SAS (SAS Institute Inc., 1996)

with treatment as the main plot and year the subplot. Data representing time trends

throughout the season (measured every 14 or 28 d and including herbage accumulation

rate, herbage mass, herbage allowance, average daily gain by period, CP, IVOMD) were









analyzed using repeated measures analysis of variance in PROC GLM of SAS (SAS

Institute Inc., 1996) with treatment as a fixed effect and sampling date as the repeated

variable. In addition to analysis of variance to determine treatment effects on forage

allowance, regression analysis was conducted using PROC REG of SAS (SAS Institute

Inc., 1996) to assess the relationship between forage allowance and heifer average daily

gain.

Results and Discussion

The average maximum temperature for both experimental periods of 2001 and

2002 was 310C, and the average minimum temperature was 190C (Table 3-6). Total

annual rainfall was 1008 and 1236 mm for 2001 and 2002, respectively (30-yr average of

1342 mm; Table 3-2). Rainfall during the experimental period was 540 mm in 2001 and

751 mm in 2002.


Table 3-6. Monthly average temperatures at the experiment site for years 2001-2002.


Temperature (OC)
2001 2002
Month Min Max Min Max
Jan 18.8 1.3 19.7 5.2
Feb 24.4 9.3 20.7 5.3
Mar 22.2 9.2 25.5 8.9
Apr 27.4 10.5 29.4 16.0
May 30.4 15.0 30.8 15.6
June 32.3 20.3 31.2 20.4
July 32.2 22.1 32.3 21.3
Aug 32.7 21.6 31.4 21.0
Sept 29.9 19.1 31.4 21.7
Oct 26.8 12.7 28.9 17.7
Nov 25.0 10.8 22.7 8.1
Dec 23.1 9.2 19.6 4.5









Herbage Mass

There was a trend toward a year effect (P=0.06) on average herbage mass, with

mass tending to be greater in 2001. This trend can be explained in part due to starting

sooner in 2002 and the experimental period including late spring/early summer. Herbage

mass values were lower and caused the seasonal average to be lower than in 2001. There

was no year X management intensity interaction for herbage mass (P=0.79; Table 3-7).

Across years, herbage mass was greater for the LOW treatment than for MODERATE or

HIGH. Bahiagrass herbage accumulation generally increases with increasing N rate

(Beaty et al., 1977; Burton, 1997; Blue, 1988), but in this experiment, the increase in

stocking rate associated with greater N rates apparently more than compensated for the

greater pasture growth rates in MODERATE and HIGH and resulted in lower herbage

mass.

The three treatments all followed a similar seasonal pattern in herbage mass

(Figures 3-1 and 3-2). Herbage mass was relatively low (1.5-2.8 Mg ha-1) early in the

grazing season, increased to a maximum, and decreased late in the season in both years.

Previous research has shown a similar pattern of herbage mass in bahiagrass pastures,

peaking in mid-summer (July August) under typical rainfall conditions (Sumner et al.,

1991; Johnson et al., 2001).

There were no intensity effects on herbage mass during any 28-d weighing periods

through the 2001 grazing season (P=0.19, P=0.20, P=0.26, and P=0.87); however, there

was a trend for the LOW treatment to have higher average herbage mass in the first three

periods. There was a management intensity X period interaction for herbage during 2002.

This occurred because herbage mass for the HIGH treatment was significantly higher









Table 3-7. Pasture herbage mass (HM) and herbage accumulation rate (HAR) responses
to management intensity of continuously stocked bahiagrass pastures.


HMt HARt
Treatment; 2001 2002 AVG' 2001 2002 AVG'
------------Mg ha-1------------ ------------kg ha-1 d1----------

Low 3.18 2.77 2.98 a 23.7 15.2 19.4 b
Moderate 2.76 2.31 2.54 b 21.3 44.5 32.9 a
High 2.69 2.44 2.56 b 30.3 43.7 37.0 a
LSD (0.05) 0.04 7.4


S.E. 0.007 1.22
There was no treatment X year interaction for HM (P=0.79) or HAR (P=0.20).

t Treatments = Low (1.2 animal units [AU] ha-1 and 40 kg N ha-1); Moderate (2.4 AU ha-1
and 120 kg N ha-1); High (3.6 AU ha-1 and 360 kg N ha-l).

Means within a column followed by the same letter are not significantly different at the
0.05 probability level.


than for LOW at the first two dates (Fig. 3-2), but by the last observation of the season,

HIGH herbage mass was significantly lower than for the LOW treatment (2.1 and 3.2 Mg

ha- ). Higher herbage mass early in the season on HIGH was likely due to a greater N

rate, but that advantage disappeared over time due to greater stocking rate than on LOW.

During mid-summer of the 2002 grazing season, there were no differences among

treatments (P=0.11, P=0.18, and P=0.16) but the trends favored the LOW treatment.

Herbage Accumulation Rate

There was no year or year X management intensity effect on average herbage

accumulation rate (P=0.19 and P=0.20), but there was an effect of management intensity

(P<0.02). This was a result of the MODERATE and HIGH treatments having greater






















3.5





2 3
2r.




I 2.5


s Low
---m--- Mod
- High


-
A-


11-Jul 8-Aug 5-Sep 3-Oct

Date


Figure 3-1. Herbage mass (HM) response to three levels of management intensity on continuously stocked bahiagrass pastures in
2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11 July (P=0.19),
8 August (P=0.20), 5 September (P=0.26), and 3 October (P=0.87). Standard errors for means on 11 July, 8 August, 5
September, and 3 October are 0.13, 0.17, 0.16, and 0.28, respectively.































=r


Low
--4- Mod
4.0 -
-i- High



3.5



aa
/ ----'; ^ ~------_--- ..,
3.0-

aab




a
2.5// '



2.0 A, ., b

bab
1.5 .


22-May


19-Jun


17-Jul


14-Aug


11-Sep


9-Oct


Date


Figure 3-2. Herbage mass (HM) response to three levels of management intensity on continuously stocked bahiagrass pastures in
2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 17 July (P=0.11),
14 August (P=0.18), and 11 September (P=0.16). Means within other dates bordered by the same letter are not different
using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11
September, and 9 October are 0.06, 0.11, 0.14, 0.19, 0.26, and 0.16, respectively.









herbage accumulation rate than the LOW treatment (Table 3-7). Previous research

(Ruelke and Prine, 1971; and Stanley, 1994) has shown bahiagrass herbage accumulation

increasing dramatically as a result of increased N fertilization. Previous studies of other

tropical grasses also show increasing herbage mass as a result of higher growth rates

under greater N application (Thom et al., 1990; Wiendenfeld, 1988). In the current study

herbage accumulation rate was greater for HIGH and MODERATE than LOW despite

LOW having greater average herbage mass. HIGH and MODERATE received more N to

increase herbage accumulation; however, the grazing pressure from the increasing SR of

these treatments removed the herbage at a faster rate, causing herbage mass to decrease.

During the 2001 grazing season (26 June to 16 October), there were no

differences in herbage accumulation rate among treatments during any 28-d period

(Figure 3-3); however, there were trends (P<0.21) favoring HIGH during three of the four

periods. The LOW and HIGH treatments followed similar patterns with decreasing

herbage accumulation from the beginning of grazing to late summer, and then slightly

increasing in early fall. The MODERATE treatment increased slightly from grazing

initiation to mid-summer, then decreased in late summer, and leveled off during early

fall.

During the 2002 grazing season (8 May to 23 October) there were no differences

in herbage accumulation rate among treatments during any 28-d period (Figure 3-4). All

treatments followed a similar trend through the grazing season, with low accumulation

rates in spring, increasing to a maximum during mid-summer, and then decreasing in late

summer/early fall. This response is similar to the herbage mass seasonal trend in 2001,

and can be explained in part by the change in temperature and rainfall at the beginning




















S-- Low
60 ---- Mod
\ -A- High


50 -




S40 -


U-
W 30 -

V '*


20

\ --"


10 Xk


n ~ ~ ~ ~ ~ ~ ~ ~ ~ ----- ----------------------------------
n
11-Jul 8-Aug 5-Sep 3-Oct

Date


Figure 3-3. Herbage accumulation rate (HAR) response to three levels of management intensity on continuously stocked bahiagrass
pastures in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11
July (P=0.14), 8 August (P=0.93), 5 September (P=0.21) and 3 October (P=0.15). Standard errors for means on 11 July, 8
August, 5 September, and 3 October are 4.5, 14.8, 19.4, and 2.5, respectively.



















-*- Low
---- Mod
-- High


-.. \

.N


22-May 19-Jun 17-Jul 14-Aug 11-Sep 9-Oct
Date


Figure 3-4. Herbage accumulation rate (HAR) response to three levels of management intensity on continuously stocked bahiagrass
pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 22
May (P=0.59), 19 June (P=0.35), 17 July (P=0.16), 14 August (P=0.12), 11 September (P=0.33), and 9 October (P=0.13).
Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 12.6, 6.5, 11.6, 12.8,
11.7 and 8.6, respectively.









and end of the growing season. The decline in growth rate experienced in mid- to late

summer, however, is more likely a response to decreasing daylength (Sinclair et al.,

2003). In both grazing seasons, herbage accumulation rate reached its maximum in mid-

July and then decreased throughout the remainder of the season. This is a typical growth

pattern for C4 grasses in this environment (Sumner et al., 1991).

Crude Protein

There was no year effect (P=0.19) on average herbage CP, nor was there a year X

management intensity treatment interaction (P=0.56). There was an effect (P<0.05) of

management intensity on herbage CP. This effect was reflected in the general increase in

CP as management intensity increased (Table 3-8). Increasing CP with greater N rates is

commonly reported for bahiagrass and other tropical grasses (Velez-Santiago and

Arroyo-Aguilu, 1983; Christiansen et al., 1988; Burton et al., 1997; Twidwell et al.,

1998). The response of bahiagrass forage CP to increased levels of N is not as large as

other tropical grasses, but the increase in bahiagrass stolon-root N is greater (Blue et al.,

1980). The reported increase in forage N harvested was 68 kg ha-1 as N increased from 0

to 336 kg ha-1 compared to 104 for Ona stargrass (Cynodon nlemfuensis Vanderyst var.

nlemfuensis). The increase in bahiagrass stolon-root N was 86 kg ha-1 compared to an

actual decrease of 3 kg ha-1 in stargrass. Therefore, even though bahiagrass herbage may

not show as great an increase in N, it is still utilized, but stored in the stolons.

During the 2001 grazing season (11 July to 3 October), there were no differences in

CP among treatments during the first 28-d period (P=0.22), but there were differences

among treatments at the remaining periods. The HIGH treatment had greater CP than

both MODERATE and LOW, and MODERATE was greater than LOW (Figure 3-5).









All treatments followed a similar seasonal trend, decreasing from mid- to late-summer,

and then remaining relatively constant for the remainder of the grazing season.


Table 3-8. Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD)
responses to management intensity of continuously stocked bahiagrass
pastures.


CPt IVOMDt
Treatment 2001 2002 AVG' 2001 2002 AVG'
---------------g kg------------------ ---------- g kg--------------

Low 92 102 97 b 426 478 452 b
Moderate 111 111 11 b 445 496 471 b
High 133 143 138 a 453 536 495 a
Average 441 b 503 a
LSD (0.05) 15 23


S.E. 2.5 3.78
There was no treatment X year interaction for CP (P=0.56) or IVOMD (P=0.57).

STreatments = Low (1.2 animal units [AU] ha-1 and 40 kg N ha-1); Moderate (2.4 AU ha-1
and 120 kg N ha-1); High (3.6 AU ha-1 and 360 kg N ha-1).

Means within a column followed by the same letter are not significantly different at the
0.05 probability level.

There was a year effect on IVOMD (P=0.02).

During the 2002 grazing season (22 May to 9 October), there were no differences

among treatments on 17 July (P=0.17), but before and thereafter there were differences

among treatments for all dates. Herbage CP for HIGH was greater than for both

MODERATE and LOW throughout the grazing season (Figure 3-6). All treatments

followed a similar seasonal pattern. Herbage CP increased to mid-summer, decreased

slightly to late summer, and then remained relatively constant level for the remainder of

the season.



















- Low
--*--Mod
--A- High


U.
\ --


120




'7100


c8

80


11-Jul


------------ -------
aa A
a


------------------------U..
b b ...

b


8-Aug


5-Sep


3-Oct


Date


Figure 3-5. Herbage crude protein (CP) response to three levels of management intensity on continuously stocked bahiagrass pastures
in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 11 July
(P=0.22). Means within other dates bordered by the same letter are not different using the least significant difference test
(P=0.05). Standard errors for means on 11 July, 8 August, 5 September, and 3 October are 7.8, 2.9, 2.3, and 1.7,
respectively.


".^
^^






















-- Low
- --Mod
-*- High


- %


7 a


a-A --------
a'- a


.*.


,-ab

,.:----- -^


100- -
b


22-May


19-Jun


.........

b
b


C


17-Jul


14-Aug


b
b


11-Sep


b--
b


9-Oct


Date


Figure 3-6. Herbage crude protein (CP) response to three levels of management intensity on continuously stocked bahiagrass pastures
in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 17 July
(P=0.17). Means within other dates bordered by the same letter are not different using the least significant difference test
(P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and 9 October are 2.6, 5.2,
9.8, 3.4, 4.5 and 5.1, respectively.









In Vitro Organic Matter Digestibility

There was a year effect on average herbage IVOMD (P=0.02). This can be

attributed in part to the inclusion of the late spring/early summer portion of the grazing

season in 2002, a time generally characterized by higher forage digestibility (Blaser,

1986). There was no year X management intensity interaction (P=0.57), but there was a

management intensity effect across years (P=0.03). The HIGH treatment had greater

IVOMD than either the LOW or MODERATE treatments (Table 3-8). Increasing N

application often has little or no effect on IVOMD ofbahiagrass and other tropical

grasses (Adjei et al., 1980; Thom et al., 1990). In the current experiment, the greater

IVOMD for the HIGH treatment is most likely due to the increase in stocking rate.

Higher stocking rate likely decreased the time period between animal visits to a given site

in the pasture. This resulted in more frequent removal of grass, causing it to be less

mature on average, thus having greater digestibility (Mislevy and Brown, 1991;

Hernandez Garay et al., in review).

During the 2001 grazing season there were no differences in herbage IVOMD

among treatments during the first three sampling periods, however, during the last

observation period of the season, IVOMD of HIGH was greater than that of LOW

(Figure 3-7). During the 2002 grazing season (22 May to 9 October), there were no

differences among treatments for the 17 July, 11 September, and 9 October periods,

however for the remaining periods there was an effect of management intensity on

IVOMD. Herbage IVOMD on HIGH was greater than on LOW on 22 May and 14

August and greater than both LOW and MODERATE on 19 June (Figure 3-8).

Generally, the treatments followed similar patterns each year, with IVOMD decreasing





















-- Low
--*--Mod
550 -Hgh
-4- High



500 -



450
I -----_._^-----_ a
> *... -ab
400

b

350



300
11-Jul 8-Aug 5-Sep 3-Oct

Date


Figure 3-7. Herbage in vitro organic matter digestibility (IVOMD) response to three levels of management intensity on continuously
stocked bahiagrass pastures in 2001. Dates are the midpoint of 28-d weighing periods. There were no differences among
treatments on 11 July (P=0.22), 8 Aug (P=0.67), and 5 September (P=0.21). Means within a date bordered by the same
letter are not different using the least significant difference test (P=0.05). Standard errors for means on 11 July, 8 August, 5
September, and 3 October are 7.1, 10.7, 11.5, and 6, respectively.















600




550
S500 .. -" a
a

bb ""i-
b --" a "----.




450
0


400



--- Low
3--5--Mod
-4- High


300
22-May 19-Jun 17-Jul 14-Aug 11-Sep 9-Oct
Date


Figure 3-8. Herbage in vitro organic matter digestibility (IVOMD) response to three levels of management intensity on continuously
stocked bahiagrass pastures in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among
treatments on 17 July (P=0.32), 11 September (P=0.59), and 9 October (P=0.11). Means within a date bordered by the
same letter are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19
June, 17 July, 14 August, 11 September, and 9 October are 7.1, 2.2, 11.6, 2.8, 20.6 and 17.3, respectively.









slowly through the season. This decrease can partly be explained by high temperatures

and increased rain through mid-summer (Jones, 1985; Wilson, 1983). An exception was

the HIGH treatment in 2002 which increased slightly during late summer/early fall. On

this heavily stocked treatment, the IVOMD likely responded this way because of

decreasing herbage mass (Fig. 3-2) and more and more frequent visits by cattle to grazing

stations in the pasture.

Herbage Allowance

There was no year effect (P=0.79) or year X management intensity interaction

(P=0.55) on herbage allowance. There was an effect (P<0.05) of management intensity

on herbage allowance, and allowance decreased as management intensity increased above

the LOW treatment (Table 3-9). This was a result of lower herbage mass and increasing

stocking rate. Increasing stocking rate increases the removal of available forage per unit

land area (Burns et al., 2003), resulting in decreasing herbage mass and allowance

(Hernandez Garay et al., in review).

Seasonal herbage allowance followed similar trends in both 2001 and 2002.

Allowance increased to a maximum in mid- to late summer and then decreased in early

fall. There were differences among treatments during all periods of the 2001 grazing

season. Allowance on the LOW treatment was greater than on HIGH during mid- to late

summer (8 August and 5 September), and greater than both HIGH and MODERATE at

the beginning and end of the season (11 July and 3 October) (Figure 3-9). During the

2002 grazing season, there were no differences among treatments on 22 May (P=0.39)

and 19 June (P=0.43), but as the season progressed, the LOW treatment had a greater

allowance than MODERATE and HIGH on 17 July. For the remainder of the season

there were differences among all treatments, with LOW having the highest allowance,



















a -*- Low
--*--Mod
a
-4- High
4.0
a



a
S3.0




U.
.-- ab
1.0 ba
O' 2.0 ... ..

S....---.-- ab ".. o00
"-- -b "- -



1-- t~~~~~ --t--------'----
b
b



0.0
11-Jul 8-Aug 5-Sep 3-Oct

Date


Figure 3-9. Herbage allowance (HA) response to three levels of management intensity on continuously stocked bahiagrass pastures in
2001. Dates are the midpoint of 28-d weighing periods. Means within a date bordered by the same letter are not different
using the least significant difference test (P=0.05). Standard errors for means on 11 July, 8 August, 5 September, and 3
October are 0.37, 0.53, 0.61, and 0.20, respectively.









followed by MODERATE and then HIGH (Figure 3-10). These trends can be explained

by the seasonal changes of herbage mass. As HM increases during mid-summer,

allowance increases and as HM decrease later in the season so does allowance. The

changes in herbage allowance are reflected in the seasonal changes in ADG, which will

be discussed later.

Table 3-9. Herbage allowance response to management intensity.


Treatment t 2001 2002 AVG "
--------kg forage kg-1 an. wt.-------

Low 4.10 3.93 4.01 a
Moderate 1.83 1.65 1.74 b
High 0.96 1.19 1.07b
LSD (0.05) 1.77


S.E. 0.29
t Treatments = Low (1.2 animal units [AU] ha-1 and 40 kg N ha-1); Moderate (2.4 AU ha-1
and 120 kg N ha-1); High (3.6 AU ha1 and 360 kg N ha-)

Means within a column followed by the same letter are not significantly different at the
0.05 probability level.

There was no treatment X year interaction for CP (P=0.55).


Average Daily Gain

There was no year effect (P=0.12) on average daily gain (ADG) nor was there a

year X management intensity interaction (P=0.65). There was an effect of management

intensity on ADG (P< 0.01). Across years, ADG decreased as management intensity

increased (Table 3-10). This did not occur because of changes in herbage nutritive value,

because it was greater for HIGH than LOW. Instead it appears to be related to quantity

of herbage, and both herbage mass and herbage allowance decreased with increased


















-- Low
--*--Mod
Mod
5 -4- High

a



C
aa

3-
0)

4 b



b--- --------- m


_. b c

C



0
22-May 19-Jun 17-Jul 14-Aug 11-Sep 9-Oct
Date


Figure 3-10. Herbage allowance (HA) response to three levels of management intensity on continuously stocked bahiagrass pastures
in 2002. Dates are the midpoint of 28-d weighing periods. There were no differences among treatments on 22 May
(P=0.39), and 19 June (P=0.43). Means within other dates bordered by the same letter are not different using the least
significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July, 14 August, 11 September, and
9 October are 0.39, 0.43, 0.45, 0.08, 0.08 and 0.06, respectively.









management intensity. Therefore, even though the herbage present was higher in

nutritive value, there was not enough herbage to support increased gains as management

intensity increased. Similar responses were observed for stargrass in Jamaica (Hernandez

Garay et al., in review) and for bermudagrass [Cynodon dactylon (L.) Pers.] in Texas

(Conrad et al., 1981).


Table 3-10. Heifer average daily gain (ADG) and gain per hectare (GPH) responses to
management intensity.


ADGt GPHt
Treatment 2001 2002 AVG' 2001 2002 AVG'
-- ----------kg d------ ------- -------------kg ha1---------

Low 0.49 0.42 0.46 a 109 143 126 b
Moderate 0.50 0.38 0.44 b 225 253 239 a
High 0.38 0.34 0.36 c 257 342 299 a
LSD (0.05) 0.01


S.E. 0.002 10
There was no treatment X year interaction for ADG (P=0.65) or GPH (P=0.70).

STreatments = Low (1.2 animal units [AU] ha-1 and 40 kg N ha-1); Moderate (2.4 AU ha-1
and 120 kg N ha-1); High (3.6 AU ha1 and 360 kg N ha-1).

Means within a column followed by the same letter are not significantly different at the
0.05 probability level.


During the 2001 grazing season there were no differences in cumulative ADG

among treatments for the 11 July (P=0.10), 8 August (P=0.67), and 3 October (P=0.21)

periods. For the 5 September period, ADG for the LOW treatment was greater than for

the HIGH treatment (Figure 3-11). During the grazing season, ADG on the LOW

treatment decreased to mid-summer, increased to late summer, and then decreased


















0.60


0.50 -





S 0.40 l

O r / ".' __
b
-*- Low
-----Mod
0.30 Mod
-A High





0.20
11-Jul 8-Aug 5-Sep 3-Oct
Date

Figure 3-11. Yearling beef heifer cumulative average daily gain (ADG) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2001. There were no differences among treatments on 25 July (P=0.10), 22
August (P=0.81), and 17 October (P=0.22). Means on 19 September bordered by the same letter are not different using the
least significant difference test (P=0.05). Standard errors for means on 8 July, 7 August, 6 September, and 1 October are
0.05, 0.06, 0.03, and 0.04, respectively.









slightly to early fall. The MODERATE treatment had a steep increase to mid summer

and then increased slightly through the remainder of the season. The HIGH treatment

increased to mid-summer, decreased to late summer, and increased slightly to early fall.

During the 2002 grazing season (22 May to 9 October), there were no differences

in cumulative ADG among treatments for the 19 June (P=0.35), 14 August (P=0.14), 11

September (P=0.21), and 9 October (P=0.45) periods. On 22 May and 17 July, ADG on

the LOW treatment was greater than the HIGH treatment (Figure 3-12). During the

grazing season, all treatments followed a similar trend, decreasing after the first

observation, then increasing and leveling off in mid-summer, and decreasing to late

summer/early fall.

Herbage allowance incorporates both pasture and animal aspects, therefore it can be

useful in explaining animal responses in trials with wide ranges of pasture herbage mass

(Hernandez Garay et al., unpublished data). These authors report a strong relationship

between increasing herbage allowance and ADG. During the 2001 season in the current

study there was no relationship between ADG and herbage mass (P=0.99). There was a

trend towards both a linear and quadratic relationship between ADG and herbage

allowance (P=0.12 and P=0.14). During 2002 there was no relationship between ADG

and herbage mass (P> 0.81) or ADG and herbage allowance (P>0.48).

Gain per Hectare

There was no year effect (P=0.19) on gain per hectare, nor was there a year X

management intensity interaction (P=0.70). There was an effect of management intensity

(P<0.05). Gain per hectare increased as management intensity increased from LOW to

MODERATE (Table 3-10) and was not different between MODERATE and HIGH.

Understocked pastures accumulate forage that becomes both underutilized and overly

















0.90 -- Low
--*--Mod

0.80 --- High


0.70 -
-. ab\

-D 0.60 -
a

S0.50 ,- -
.
0.40 '


0.30 -


0.20


0.10
22-May 19-Jun 17-Jul 14-Aug 11-Sep 9-Oct
Date

Figure 3-12. Yearling beef heifer cumulative average daily gain (ADG) response to three levels of management intensity on
continuously stocked bahiagrass pastures in 2002. There were no differences among treatments on 19 June (P=0.35), 14
August (P=0.14), 11 September (P=0.21), and 9 October (P=0.45). Means within other dates bordered by the same letter
are not different using the least significant difference test (P=0.05). Standard errors for means on 22 May, 19 June, 17 July,
14 August, 11 September, and 9 October are 0.05, 0.10, 0.01, 0.02, 0.03, and 0.04, respectively.









mature. Increasing SR increases forage utilization thus increasing animal production on a

per unit land area basis (Mott and Lucas, 1952). Conrad et al. (1981) reported similar

results on bermudagrass, however they noted that an increase in production per unit land

area can only increase to a certain extent, and then the forage genetics become the

limiting factor. On similar tropical forages, intake per animal decreases with increasing

SR; however, higher percentages of the seasonal DM yield are utilized per unit land area,

thus increasing production per unit land area (Adjei et al., 1980).

Bahiagrass Cover

There was a management intensity effect on percentage unit change in bahiagrass

cover (P=0.02) during 2 yr of grazing. The HIGH treatment had a positive effect on

percent bahiagrass cover (7.1%) and the LOW and MODERATE treatments both had a

negative effect (-6.4 and -4.7%). This negative change was predominantly due to the

invasion of vaseygrass (Paspalum urvillei Steud) and smutgrass [Sporobolus indicus (L.)

R. Br.], both of which are bunch grass weeds. Some grass weed species such as

vaseygrass are palatable to cattle at immature growing stages and are grazed

(Sollenberger et al., 1997). With increasing management intensity, greater SR increases

the frequency of animal visits to a given site in a pasture. This may result in more

frequent grazing of herbage, including weeds, such that they remain more palatable to

cattle. Newman et al. (2003) found a greater decrease ofvaseygrass plant density in

limpograss [Hemarthria altissima (Poir.) Stapf & Hubb.] pastures when forage was

grazed to 20 cm as opposed to 40 and 60 cm. The loss in vaseygrass plant density was

attributed to its inability to adequately refoliate and restore carbohydrate reserves after

consecutive grazing events. This along with the low growth habit and strong ability for

photosynthesis or a sizeable carbohydrate reserve from which to draw for regrowth of









bahiagrass (Beaty et al., 1970) allows it to out compete the weedy bunch grasses under

heavier grazing pressure.

Summary and Conclusions

The objectives of this research were to assess the effects of management intensity

on forage and yearling beef heifer performance in Pensacola bahiagrass. For this

experiment, management intensity was defined as a combination of a N fertilizer rate and

an animal stocking rate and levels of intensity were chosen to reflect and extend those

used by beef producers in Florida. The three management intensity treatments were

LOW (40 kg N ha-1 yr-1, 1.2 animal units [AU, one AU=500 kg live weight] ha-1 stocking

rate), MODERATE (120 kg N ha-1 yr1, 2.4 AU ha-1 stocking rate), and HIGH (360 kg N

ha-1 yr1, 3.6 AU ha-1 stocking rate), and treatments were arranged in two replicates of a

randomized block design.

As management intensity increased, heifer average daily gain, pasture herbage

mass, and herbage allowance decreased. However, nutritive value, gain per hectare,

herbage accumulation rate, and bahiagrass cover increased as a result of increased

management intensity. As management intensity increased above the LOW treatment,

production per unit land area increased, but at a large cost in relation to additional N cost.

Gain per hectare increased 113 kg ha-1 as management intensity increased from LOW to

MODERATE at an additional cost of $60 for N fertilizer (This does not include the

additional cost of P and K applications for MODERATE and HIGH during 2002). This

equals a cost of $0.53 of fertilizer per additional kg of gain above LOW. As management

intensity increased to HIGH, there was a 173 kg ha-1 increase in gain per hectare. With

the cost of additional fertilizer ($206), the cost of fertilizer per additional kg of gain

equaled $1.21.






57


From the results of this research, it is apparent that very high N rates will not

produce gains that will make these strategies economically feasible for beef producers. If

the need arises for producers to increase production on decreased land area, the

replacement of bahiagrass with another more management responsive species will be

required.














CHAPTER 4
GRAZING METHOD EFFECTS ON FORAGE GROWTH AND NUTRITIVE
VALUE OF BAHIAGRASS PASTURES

Introduction

High yield of high quality forage is critical for maximizing animal production on

pasture. As grassland is converted to non-agricultural uses in increasingly urban states

like Florida, maintaining production levels on a decreasing land resource may become

difficult. Intensification of management is one option for achieving the desired increase

in production per unit land area. Choice of a grazing method is an important

management decision that may affect animal production on grazed pasture (Ball et al.,

1996).

Changing from continuous to rotational stocking has the potential to increase

forage production, reduce amount of forage wasted, and in turn increase stocking rates

(Blaser, 1986). This increase in stocking rate may allow for higher animal performance

on a per unit land area basis. Potential exists to improve pasture performance by altering

the number of pasture subdivisions, i.e., length of the grazing period in rotationally

stocked pastures.

Comparisons of bahiagrass pasture performance are limited under a wide range of

grazing management practices. The objectives of this experiment were to evaluate the

effect of continuous and a range of rotational stocking methods on herbage accumulation,

herbage nutritive value, and persistence of bahiagrass.









Methods and Materials

Experiment Site

The experiment was conducted at the Beef Research Unit located northeast of

Gainesville, FL (290 43' N lat.). Pastures used were well-established swards of Pensacola

bahiagrass that had been stocked rotationally at similar stocking rates (1.5 animal units

[AU, one AU=500 kg live weight] ha-1) during the previous five summer grazing seasons.

Soils at the site are predominantly of the Pomona and Smyrna series of sandy Spodisols

with average pH of 5.7. Soil P, K, Ca, and Mg concentrations were 3, 33, 450, and 82

mg kg-1, respectively.

Treatments and Design

There were five treatments arranged in a randomized block design with two

replicates. Treatments were continuous stocking and four rotationally stocked pastures

differing only in length of grazing period (1, 3, 7, and 21 d). Length of rest period

between grazings was 21 d for all four rotational stocking treatments. All pastures were

fertilized at 270 and 360 kg N ha-1 in 2001 and 2002 (Table 4-1), respectively, and had a

beginning stocking rate of 4.1 and 4.0 AU per hectare in the 2 yr.


Table 4-1. Nitrogen application dates and rates for bahiagrass pastures.

N application dates (rates in kg ha-1)
2001 2002

13 June (90) 30 Apr (40)
20 July (90) 14 May (50)
24 Aug (90) 12 June (90)
15 July (90)
20 Aug (90)









Grazing began in the spring of 2001 and 2002 when quantity of forage was

sufficient to support treatment stocking rates. Paddock size for 21-, 7-, 3-, and 1-d

residence period treatments were 0.5, 0.25, 0.125, and 0.045 ha, respectively.

Comparison of animal performance was not an objective of this experiment, so in effect,

the area used for the rotational stocking treatments was that needed for one pasture

subunit (paddock) of the complete rotational grazing system. For example, the 21-d

residence period treatment would require two paddocks if animal performance was to be

measured, one in which grazing would currently be underway, another which was

regrowing. In this experiment, we had only one paddock per replicate. Thus during the

21-d rest periods when cattle were not grazing this paddock, they were on other

treatments in the experiment. Cattle groups of the appropriate live weight were moved

among the rotational stocking treatments whenever a given paddock was scheduled for

grazing. In 2001, the 21-, 7-, 3-, and 1-d treatments were grazed 3, 4, 5, and 6 times

respectively, while in 2002, they were grazed 4, 6, 6, and 7 times.

The target stocking rate used was that of the HIGH treatment from Experiment 1

(Chapter 3), i.e., 3.6 AU hal-. Actual rates were somewhat higher due to higher than

expected cattle initial weights. Thus, all rotational treatments were stocked with

approximately the same number of kg of live weight for the designated length of

residence period. This resulted in very different stocking densities (short-term measure

of animals per unit land area), but the stocking rate over a complete grazing cycle (time

during which each paddock in an actual system would be visited once) was the same for

all treatments. This allowed evaluation of the effects of the different grazing strategies

on pasture accumulation rate, nutritive value, and percent bahiagrass cover.









Pasture Measurements

For rotationally stocked paddocks, sampling occurred the day prior to the start of

each grazing period and the day the grazing period ended. Thirty disk meter

measurements were taken throughout each paddock at each sampling to determine

herbage mass. The disk meter was calibrated every 28 d as described in Chapter 3.

Herbage accumulation was calculated as pregraze herbage mass of the current cycle

minus postgraze herbage mass of the previous cycle. Herbage mass, herbage

accumulation, and herbage accumulation rate for the continuous treatment were

quantified as described in Chapter 3.

Nutritive value for the five treatments was assessed using hand-plucked samples.

The approach for the continuous treatment has already been described in Chapter 3. For

the rotational stocking treatments, sampling occurred just before the beginning of each

grazing period. For these treatments, herbage was sampled to a stubble that

approximated what the animals would remove during the grazing period. This was based

on the postgraze stubble height of recently defoliated treatments. Samples were dried at

600C for 48 h, ground to pass a 1-mm screen in a Wiley Mill, and analyzed for crude

protein (CP) and in vitro organic matter digestibility (IVOMD) as described in Chapter 3.

Bahiagrass cover was estimated visually at the beginning and end of each grazing

season. Five equally spaced line transects were established for each paddock. Percent

bahiagrass was estimated visibly at eight locations along each transect for a total of 40

observations per paddock. Data reported are changes in percent bahiagrass cover from

before the experiment started through two grazing seasons later.









Statistical Analyses

Data representing annual averages (e.g., average herbage accumulation rate,

average herbage CP and IVOMD, and change in bahiagrass cover) were analyzed using

analysis of variance in PROC GLM of SAS with treatment as the main plot and year as

the subplot. Data representing time trends throughout the season herbagee accumulation

rate, CP, and IVOMD) were analyzed using repeated measures analysis of variance in

PROC MIXED of SAS with treatment as a fixed effect and sampling period as the

repeated variable. Periods were identified because rotational treatments were grazed at

different dates and different numbers of times throughout the year. The periods were

early summer (25 June 11 July 2001 and 15 May 11 July 2002), mid-summer (12 July

- 29 August each year), and late summer (30 August- 21 October each year). Means for a

given period represent data from one or two grazing cycles for rotational treatments,

depending on treatment.

Results and Discussion

Herbage Accumulation Rate

There was no year or year X management intensity effect on average herbage

accumulation rate (P=0.33 and P=0.61), but there was an effect of management intensity

(P=0.05). All the rotational treatments had greater herbage accumulation rate than the

continuous treatment (Table 4-2). To maximize herbage accumulation requires

maximum interception of light by leaf. This is achieved by increasing leaf area index

(LAI, ratio of area of leaf in the canopy to the area of ground below) which allows for a

greater proportion of radiation to be intercepted by the canopy (Chapman and Lemaire,

1993). Optimal LAI is that which allows 95 to 100% light interception (Donald, 1961),

and this is achieved more quickly over time if grazing pressure is reduced. After









defoliation, energy for regrowth is derived from mobilization of carbohydrate reserves

(Gerrish, 1991). The rest period between defoliations allows swards to accumulate leaf

area and restore carbohydrate reserves (Chaparro et al., 1996). Although not quantified

in this study, the greater herbage accumulation rates for rotational treatments suggest that

average LAI and canopy light interception were greater for rotationally than continuously

stocked bahiagrass swards.


Table 4-2. Herbage accumulation rate (HARt) response to grazing method on bahiagrass
pastures.


Treatment



Rot.-l1
Rot.-3
Rot.-7
Rot.-21
Cont.


LSD (0.05)


2001 2002 Average
------------- kg ha- d-1--------

65 60 63 a
52 84 68 a
68 75 72 a
78 80 79 a
30 44 36 b


S.E.


SThere was no treatment X year interaction for HAR (P=0.61).

t Grazing methods are rotational (Rot.) and continuous (Cont.). The number following
Rot. is the length of the grazing period in days, while the rest period was a constant 21 d
for all rotational treatments.

Means within a column followed by the same letter are not significantly different at the
0.05 probability level.









Herbage accumulation rates of rotational treatments followed similar patterns

during the 2001 grazing season, increasing from early to mid-summer, and then

decreasing in early fall. The continuous treatment decreased accumulation rates

throughout the grazing season (Table 4-3). The shorter grazing period treatments (1 and


Table 4-3. Seasonal pasture herbage accumulation rate (HARt) response to grazing
method on bahiagrass pastures.


2001 Season1 2002 Season
Treatment 1 2 3 1 2 3
----- ---------------------kg ha d-------------------
Rot.-1 78 a# 87 a 50 ab 69 80 56 a
Rot.-3 60 a 76 ab 28 ab 67 102 93 b
Rot.-7 56 a 75 ab 57 ab 77 105 57 a
Rot.-21 71 a 84 a 74 a 90 79 91 b
Cont. 48 a 32 b 14 b 42 62 44 a


S.E. 20 18 18 25 19 10

tThere was no treatment X year interaction for HAR (P=0.61).

2001 Seasons= 1 (25 June- 11 July); 2 (12 July- 29 August); and 3 (30 August- 16
October).

2002 Seasons= 1 (15 May- 11 July); 2 (12 July- 29 August); and 3 (30 August- 21
October).

Grazing methods are rotational (Rot.) and continuous (Cont.). The number following
Rot. is the length of the grazing period, while the rest period was a constant 21 d for all
rotational treatments.

# Means within a season followed by the same letter are not significantly different
(P<0.05) by repeated measures ANOVA contrasts.


3 d) experienced a more rapid decline in accumulation rate in early fall, while the longer

grazing period treatments (7 and 21 d) had a less pronounced decline. The last sampling









dates of the short grazing period treatments fell in early to mid-October, and herbage

accumulation rates ranged from -28.6 to 16.5 kg ha-1 d1, while the longer grazing period

treatments ended in mid- to late September and ranged from 50.2 to 83.3 kg ha- d-1. This

partly explains the sharper decrease in herbage accumulation for the 1- and 3-d

treatments as well as the overall trend toward lower total-season accumulation rates

(Table 4-2). Lower accumulation rates for bahiagrass in fall have been attributed to plant

responses to shorter daylength (Sinclair et al., 2003). During the 2002 season, all but the

21-d rotational treatment followed similar trends (Table 4-3), increasing from grazing

initiation to mid-summer, and then decreasing to late summer/early fall.

Crude Protein

There was a year effect on herbage CP (P=0.02). The difference between years can

be attributed in part to less N being applied in 2001 than in 2002, however, the lower N

rate in 2001 was also associated with a shorter grazing season. In addition, during 2001

relatively heavy rainfall occurred the day of, and during the 3 d immediately following N

application on 13 June and 20 July (26 and 43 mm, respectively). During the 2002,

season rainfall the day of and 3 d following N application was less than 10 mm for all but

the last application. The greater rainfall after application in 2001 may have caused N to

leach through the soil more quickly making it less available for uptake, and possibly

contributing to the lower CP values in 2001. There was no year X treatment or treatment

effect on herbage CP (P=0.29 and P=0.24) (Table 4-4). Previous studies with bahiagrass

have shown potentially large increases in production and forage N concentration with

increasing N rate (Blue, 1998), however, in this trial all treatments received the same N

rate and no effect of grazing method was observed. Williams and Hammond (1999) also

found no differences in CP when comparing rotational (7 d grazing, 21 d rest) and









Table 4-4. Herbage crude protein (CP) and in vitro organic matter digestibility (IVOMD)
responses to stocking method on bahiagrass pastures.


CPt


Treatment ;



Rot.-l1
Rot.-3
Rot.-7
Rot.-21
Cont.

Average

LSD (0.05)


2001 2002 AVG'
------------------g kg-----------

132 144 138 a
140 152 146 a
143 148 146 a
148 150 149 a
133 143 138 a
139 b 147 a


IVOMDt
2001 2002 AVG'
-1
-----------g kg--------

496 555 526 a
500 572 536 a
508 513 511 a
514 544 529 a
453 536 493 b
494 b 544 a


S.E. 3.5 4.5
There was no treatment X year interaction for CP (P=0.29) or IVOMD (P=0.12).

t Grazing methods are rotational (Rot.) and continuous (Cont.). The number following
Rot. is the length of the grazing period in days, while the rest period was a constant 21 d
for all rotational treatments.

Means within a column followed by the same letter are not significantly different at the
0.05 probability level.

There was a year effect on CP(P=0.02) and IVOMD (P<0.01).


continuous stocking of bahiagrass when pastures were fertilized and stocked at the same

level (70 kg N ha-1 and 2.1 to 2.4 head ha-1, respectively). Bermudagrass [Cynodon

dactylon (L.) Pers.] also showed little difference in CP between rotational (15 paddocks

with 1.5- 2.5 d grazing period, and paddocks with 10-14 d grazing periods) and

continuous stocking at equal levels of N and stocking rate (210 kg N ha-1 and 1.5 AU

ha-) (Matthews et al., 1994).









Seasonal patterns in herbage CP among treatments during the 2001 grazing season

followed similar trends (Table 4-5). All treatments decreased from early and mid-

summer to late summer and increased in late summer. During the 2002 grazing season,

the longer grazing period rotational treatments (7 and 21 d) followed a similar pattern to

that in 2001. The short grazing period (1 and 3 d) rotational treatments and the

continuous treatment showed little seasonality of response (Table 4-5).

Table 4-5. Seasonal herbage crude protein (CP) response to grazing method on
bahiagrass pastures.


2001 Seasont 2002 Season1
Treatment 1 2 3 1 2 3
---------------------------------g kg--------------------------------

Rot.-1 166 ab 128 138 b 146 155 141
Rot.-3 173 a 134 146 a 155 158 148
Rot.-7 174 a 134 148 a 160 144 150
Rot.-21 167 ab 127 165 a 164 143 149
Cont. 150 b 132 137 b 144 148 146


S.E. 7.8 5.1 4.9 8.0 8.1 8.1
'2001 Seasons= 1 (25 June- 11 July); 2 (12 July- 29 August); and 3 (30 August- 16
October).

2002 Seasons= 1 (15 May- 11 July); 2 (12 July- 29 August); and 3 (30 August-
21 October).

Grazing methods are rotational (Rot.) and continuous (Cont.). The number following
Rot. is the length of the grazing period, while the rest period was a constant 21 d for all
rotational treatments.

SMeans within a season followed by the same letter are not significantly different
(P<0.05) by repeated measures ANOVA contrasts.









In Vitro Organic Matter Digestibility

There was a year effect (P<0.01), but there was no year X treatment (P=0.12)

interaction effect on IVOMD. Greater IVOMD in 2002 than 2001 occurred primarily due

to very large differences between years from mid-summer through early fall. Reasons for

this difference are not readily apparent. There was a treatment effect on IVOMD

(P=0.01) because the rotational treatments had greater IVOMD than the continuous

treatment (Table 4-4). At the same stocking rate, rotationally stocked animals are

restricted to smaller area of pasture at a given point in time than continuously stocked

animals causing animals to be less selective and graze lower in the canopy (Bransby,

1991). This may tend to reduce overall diet digestibility or it may increase it over time

because it limits the build up of mature or senescent herbage. For these reasons and

perhaps because it is difficult to sample a diet comparable to that selected by the animal,

the literature does not show a consistent pattern of IVOMD response to grazing method.

For example, Williams and Hammond (1999) found IVOMD to be similar in an

experiment comparing rotational and continuous stocking on bahiagrass; however,

research on bermudagrass suggests a trend toward higher IVOMD for rotational over

continuous stocking (Matthews et al., 1994).

During 2001, seasonal changes in IVOMD followed a similar pattern across all

treatments, decreasing as the grazing season progressed (Table 4-6). This pattern could

possibly be explained by the greater loss of water soluble carbohydrates associated with

increased respiration due to increased temperatures associated with mid-summer and

early fall (Jones, 1985). Another possible explanation could be the decrease in herbage

accumulation rates as the season progressed. With lower accumulation rates, cattle are

forced to graze lower in the canopy and this herbage is more mature and includes more









senescent material. There were also differences among treatments during each seasonal

period. During the early summer, all rotational treatments had significantly higher

IVOMD than continuous. However, IVOMD for all rotational treatments, except the 21

d, decreased more severely through the season, so by early fall, only the 21-d rotational

was higher than the continuous treatment.


Table 4-6. Seasonal herbage in vitro organic matter digestibility (IVOMD) response to
grazing method on bahiagrass pastures.


2001 Seasont 2002 Season1
Treatment 1 2 3 1 2 3
--------------------------------g kg---------------------------
Rot.-1 579 a 510 a 472 ab 569 a 559 543 ab
Rot.-3 599 a 520 a 450 ab 568 a 556 565 a
Rot.-7 616 a 494 ab 468 ab 514b 513 512b
Rot.-21 579 a 508 a 494 a 533 ab 544 566 a
Cont. 537 b 442 b 432 b 557 ab 525 525 ab


S.E. 14.5 20.0 16.9 18.5 25.9 16.5
'2001 Seasons= 1 (25 June- 11 July); 2 (12 July- 29 August); and 3 (30 August- 16
October).

2002 Seasons= 1 (15 May- 11 July); 2 (12 July- 29 August); and 3 (30 August-
21 October).

Grazing methods are rotational (Rot.) and continuous (Cont.). The number following
Rot. is the length of the grazing period, while the rest period was a constant 21 d for all
rotational treatments.

SMeans within a season followed by the same letter are not significantly different
(P<0.05) by repeated measures ANOVA contrasts.


During the 2002 season, all treatments decreased or remained relatively constant in

IVOMD from late spring/early summer to fall except for the 21-d treatment which

increased as the season progressed (Table 4-6). During late spring/early summer,









IVOMD for the 1- and 3-d rotational treatments was higher than for the 7-d treatment.

During the mid-summer there were no differences among treatments. By the early fall,

the 1-d treatment had decreased, and the 21-d treatment had increased so that the 3- and

21-d treatments were higher than the 7-d treatment (Table 4-6).

Bahiagrass Cover

Grazing method affected bahiagrass cover (P<0.01). Continuous stocking had a

positive effect on bahiagrass cover while all rotational treatments caused bahiagrass

cover to decrease, especially the 1-d treatment (Table 4-7). This response was

Table 4-7. Changes in bahiagrass cover in response to grazing method in bahiagrass
pastures.


June December
Treatment 2001 2002 Change
--------------------%-------------------

Rot.-1 96.2 80.6 -15.6 a
Rot.-3 84.9 81.2 -3.7 b
Rot.-7 85.1 80.5 -4.6 b
Rot.-21 88.8 80.4 -8.4 b

Cont. 80.6 87.7 7.1 c


LSD (0.05) 6.7


S.E. 1.7


tGrazing methods are rotational (Rot.) and continuous (Cont.). The number following
Rot. is the length of the grazing period, while the rest period was a constant 21 d for all
rotational treatments.

Means followed by the same letter are not significantly different (P<0.05) by LSD
ANOVA contrast









unexpected, even for a very grazing tolerant species like bahiagrass. Stocking rate was

the same across treatments, so it should not have affected the response. Herbage

accumulation rate was actually greater on the rotational treatments, so grazing pressure

was less than on the continuous treatment. The major change in species composition of

the rotational pastures was greater presence of vaseygrass (Paspalum urvillei Steud.) and

smutgrass [Sporobolus indicus (L.) R. Br.]. Both of these species become unpalatable to

livestock at relative young growth stages (Newman et al., 2003; Adjei et al., 2003). It

can be hypothesized that the more frequent visits by cattle to a particular grazing station

under continuous stocking may result in these species being kept in check to a greater

degree than under a 21-d rest period rotational system. It is not clear, however, why

bahiagrass cover decreased to a greater extent on the 1-d treatment than the other

rotational pastures.

Summary and Conclusions

As agricultural land continues to diminish due to conversion to urbanized area by

the increasing human population, increasing animal production per unit land area may

become more and more important to producers in order to maintain financial stability.

Stocking rate decisions greatly affect animal productivity, but stocking method also has

the potential to influence animal performance.

The objectives of this experiment were to evaluate the effect of continuous and a

range of rotational stocking methods on herbage accumulation rate, herbage nutritive

value, and persistence of bahiagrass pastures. Herbage accumulation and herbage

IVOMD were greater for rotationally than continuously stocked pastures. Herbage

accumulation rate did not differ among rotational treatments, and there was no effect of

grazing method on CP. Bahiagrass cover decreased for rotationally stocked pastures (-









8.1% average among rotational treatments) but increased under continuous stocking

(7.1%). Among rotational treatments, bahiagrass cover decreased more for the 1-d than

the average of the other three treatments (-5.6 to -15.6%).

With the utilization of rotational as opposed to continuous stocking, there is

potential to increase herbage growth rates which in turn, could support greater stocking

rates. However high N fertilization combined with rotational grazing appears to pose the

threat of increased invasion of vaseygrass and smutgrass in bahiagrass pastures, thus

necessitating more intensive weed control management as well. These data show no

consistent advantage in any production response of very short grazing periods (1 or 3 d)

on rotationally stocked bahiagrass pastures.














CHAPTER 5
SUMMARY AND CONCLUSIONS

The beef industry is a critical component of Florida's large agriculture industry.

Revenues from the beef cattle industry in Florida totaled 371 million dollars in 2000 and

accounted for 5.3% of the total agricultural cash receipts (Florida Agricultural Facts

Directory, 2002). Grasslands cover large areas of land in both Florida and the

southeastern USA and are an important source of feed to the livestock industry.

Bahiagrass serves as an essential resource to the beef industry covering approximately 1

million hectares in Florida (Chambliss, 2000). However, with the large increase in

human population over the past 40 yr and projected increases in the next 30 yr,

urbanization poses a threat to the amount of land available for agricultural uses. The

livestock industry may be forced to maintain economic livelihood on smaller amounts of

land. A potential solution to this problem is to increase management intensity on smaller

amounts of land to attain equal or greater production.

With this situation in mind, the research conducted focused on animal performance

and pasture characteristics of grazed bahiagrass pastures as influenced by increasing

management intensity. Management intensity was defined by stocking rate, N

fertilization rate, and grazing method, and the research was divided into two experiments.

The first experiment evaluated beef heifer performance and pasture responses to

three levels of management intensity of continuously stocked bahiagrass pastures.

Intensity levels were defined by N fertilizer rate and stocking rate and included LOW (40

kg N ha-1 yrf1, 1.2 animal units [AU, one AU=500 kg live weight] ha-1 stocking rate),









MODERATE (120 kg N ha-1 yr-1, 2.4 AU ha- stocking rate), and HIGH (360 kg N ha-

yr-1, 3.6 AU ha-1 stocking rate), and were intended to represent and extend the current

practice of producers in Florida. Animal performance was evaluated on a per animal

basis (average daily gain) and a per unit land area basis (gain per hectare). Pasture

responses included nutritive value, herbage mass, herbage allowance, and herbage

accumulation.

As management intensity increased, heifer average daily gain and pasture herbage

mass and allowance decreased. However, gain per hectare, herbage nutritive value,

herbage accumulation rate, and bahiagrass cover increased as a result of increased

management intensity. Both herbage mass and allowance decreased as management

intensity increased above the LOW to the HIGH treatment (3.0 to 2.6 Mg ha-1 and 4.0 to

1.1 kg forage kg-1 an. wt., respectively) as a result of the greater proportional increase in

stocking rates compared to accumulation rate. Heifer ADG and pasture herbage mass

and allowance generally followed similar trends throughout the season. Heifer ADG

decreased, but the response was relatively small, only decreasing 0.10 kg d-1 as

management intensity increased from the LOW to HIGH treatment. Both herbage CP

and IVOMD increased as management intensity increased. Increases in CP (97 to 138 g

kg-1) from the LOW to HIGH treatment were caused in part by the increase in N

application. The observed increase in herbage IVOMD from the LOW to HIGH

treatment (452 to 495 g kg-1) is not a typical response to increased N fertilization, but it

can be explained by the increase in SR which likely increased the frequency of visits per

site in the pasture. This prevented underutilization and accumulation of mature herbage.









Production per unit land area increased as management intensity increased above

the LOW treatment, but at a large cost in relation to additional N cost. As management

intensity increased from the LOW to the MODERATE level, gain per hectare increased

110 kg ha-1. However with the cost of additional N being 60 dollars, the cost of fertilizer

per additional kg of gain was $0.55. As management intensity increased from LOW to

HIGH, gain per hectare increased 170 kg ha-1. The cost of additional N was $206;

therefore the cost of fertilizer per additional kg of gain was $1.21. From this it is

apparent that very high N rates on bahiagrass are not likely to be economically feasible

for beef producers.

The second experiment evaluated continuous and a range of rotational stocking

methods on herbage accumulation rate, herbage nutritive value, and persistence of

bahiagrass pastures. In this experiment there were five treatments, including four

rotational treatments differing only in length of the grazing period, and one continuous

stocking treatment. The rotational treatments had grazing periods of 1, 3, 7, and 21-d, all

with a 21 d rest period. All treatments received the same N fertilization and stocking

rate of the HIGH treatment from the first experiment.

Changing from continuous to rotational stocking increased herbage accumulation

and IVOMD. There were no differences among rotational treatments in herbage

accumulation rate; however, there was a trend toward increasing accumulation rate as

length of grazing period increased (63 to 79 kg ha-1 d-1). Use of rotational compared with

continuous stocking decreased bahiagrass cover (-8.1% average among rotational

treatments compared to +7.1% for continuous). Among rotational treatments, bahiagrass









cover decreased more for the 1-d treatment than for the other grazing periods (-15.6 % vs.

-3.7). These treatments had no effect on herbage CP.

These experiments showed that bahiagrass pastures were responsive to increased

management intensity, but high levels of N fertilization appear to be associated with

significant concerns including insufficient increase in animal production relative to N

costs, greater weed invasion with rotational stocking, and, although not an objective of

these experiments, greater potential for loss of nutrients to the environment. Rotational

stocking increased herbage accumulation rate, which in practice would allow for a greater

stocking rate and production per unit land area, but rotational stocking in conjunction

with high N fertilizer rates resulted in large increases in cover by vaseygrass and

smutgrass. Among rotational stocking treatments, there were no measurable advantages

to increasing the number of paddocks (decreasing the grazing time per paddock) per

pasture. In conclusion, these data suggest that modest increases in management intensity

of bahiagrass pastures may be warranted, specifically rotational stocking (2-4 paddocks)

and increasing N rate to approximately 120 kg ha-1 yr-. However, higher rates of N

fertilizer do not appear to have merit from either an economic or a pasture-persistence

perspective in addition to increase potential for negative environmental impacts.

Therefore, if the need for increased production per unit land areas becomes acute in

Florida forage-livestock systems, the use of other more management-responsive grasses

will likely be required.

This research also points to the need for further research in related areas. There is

the possibility of imposing these or similar management practices on one or more forage

species that have the potential to respond more favorably than bahiagrass. This research






77


may provide useful data for development of models that can be helpful in assessing

sustainability in an increasingly urban society.
















LIST OF REFERENCES


Adjei, M.B., P. Mislevy, R. Kalmbacher, and P. Busey. 1989. Production, quality, and
persistence of tropical grasses as influenced by grazing frequency. Soil Crop Sci.
Soc. Fla Proc. 48:1-6.

Adjei, M.B., P. Mislevy, K.H. Quesenberry, and W.R. Ocumpaugh. 1988. Grazing-
frequency effects on forage production, quality, persistence and crown total non-
structural carbohydrate reserves of limpograss. Soil Crop Sci. Soc. Fla Proc.
47:233-236.

Adjei, M.B., P. Mislevy, and C.Y. Ward. 1980. Response of tropical grasses to stocking
rate. Agron. J. 72:863-868.

Adjei, M.B., J.J. Mullahey, P. Mislevy, and R. Kalmbacher. 2003. Smutgrass control in
perennial grass pastures. Univ. of Fla SS-AGR-18.

Arndorfer, B. 2003. County projected to grow by 41 percent, pp. 1 The Gainesville Sun,
Final Edition, Gainesville, FL. 12 Feb.

Ball, D.M., C.S. Hoveland, and G.D. Lacefield. 1996. Grazing management, p. 182-196.
In Southern Forages, 2nd ed. Potash and Phosphate Institute, Norcross, GA.

Beaty, E.R., R.H. Brown, and J.B. Morris. 1970. Response of Pensacola bahiagrass to
intense clipping. p. 538-542. In M.J.T. Norman (ed.) Proc. Int. Grassl Congr., 11th.
Surfers Paradise, Qld., Australia. 13-23 Apr. 1970. Univ. of Qld. Press, Santa
Lucia, Qld., Australia.

Beaty, E.R., J.L. Engel, and J.D. Powell. 1977. Yield, leaf growth, and tillering in
bahiagrass by N rate and season. Agron. J. 69:308-311.

Blaser, R.E. 1986. Forage-animal management systems. Virginia Agric. Exp. Stn. Bull.
86-7, Blacksburg, VA 24061.

Blue, W.G. 1988. Response of Pensacola bahiagrass on a Florida spodosol to nitrogen
sources and times of application. Soil Crop Sci. Soc. Fla Proc. 47:139-142.

Blue, W.G., C.L. Dantzman, and V. Impithuksa. 1980. The response of three perennial
warm-season grasses to fertilizer Nitrogen on an eaugallie fine sand (Alfic
Haplaquod) in central Florida. Special Report, Ag. Exp. Stn., Univ. of Ark. 9:44-
47.









Bransby, D.I. 1991. Implications of rotational and continuous grazing: a case for
continuous grazing. p. 10-14 In Proc. Am. Forage Grassl. Conf., Columbia, MO. 1-
4. Apr. 1991. Am. Forage Grassl. Council, Georgetown, TX.

Burns, J.C., J.G. McIvor, L. Villalobos M., R.R. Vera, and D.I. Bransby. 2003. Grazing
systems. In L.E. Moser et al. (ed.) Warm-season (C4) grasses. ASA, CSSA.
Madison, WI.

Burson, B., and V. Watson. 1995. Bahiagrass, dallisgrass, and other Paspalum species, p.
431-434, In R. Barnes et al., (eds.) Forages Volume I: An Introduction to Grassland
Agriculture. Iowa State University Press, Ames, Iowa.

Burton, G.W., R.N. Gates, and G.J. Gascho. 1997. Response of Pensacola bahiagrass to
rates of nitrogen, phosphorus and potassium fertilizers. Soil Crop Sci. Soc. Fla
Proc. 56:31-35.

Chambliss, C. 2000. Bahiagrass. UFL SS-AGR-36. Univ. of Fla. Gainesville, FL.

Chaparro, C.J., L.E. Sollenberger, and K.H. Quesenberry. 1996. Light interception,
reserve status, and persistence of clipped Mott elephantgrass swards. Crop Sci.
36:649-655.

Chapman, D.F., and G. Lemaire. 1993. Morphogenetic and structural determinants of
plant regrowth after defoliation. p. 95-104. In Proc. Int. Grassl. Congr., 17th
Rockhampton, Australia. 8-21 Feb. 1993. Dunmore Press Ltd., Palmerston North,
New Zealand.

Christiansen, S., O.C. Ruelke, W.R. Ocumpaugh, K.H. Quesenberry, and J.E. Moore.
1988. Seasonal yield and quality of'Bigalta', 'Redalta' and 'Floralta' limpograss.
Trop. Ag. 65:49-55.

Conrad, B.E., E.C. Holt, and W.C. Ellis. 1981. Steer performance on Coastal, Callie and
other hybrid bermudagrasses. J. Anim. Sci. 53:1188-1192.

Cuomo, G.J., D.C. Blouin, D.L. Corkern, and J.E. McCoy. 1996. Plant morphology and
forage nutritive value of three bahiagrasses as affected by harvest frequency. Agron
J 88:85-89.

DiRienzo, D.B., K.E. Webb Jr., D.E. Brann, and M.M. Alley. 1991. Effect of spring
nitrogen application on barley forage yields and silage fermentation. J. Prod. Agric.
4:39-44.

Donald, C.M. 1961. Competition for light in crops and pastures. Symposium of the Soc.
of Exp. Bio. 15:282-313.

Faria, J.R., B. Gonzalez, J. Faria-Marmol, and D.E. Morillo. 1999. Effect of nitrogen and
phosphorus fertilizers on some components of nutritive value of dwarf
elephantgrass. Comm. Soil Sci. Plant Anal. 30:2259-2266.









Florida Dept. of Ag. and Cons. Services. 2002. Agricultural Fast Facts. Tallahassee, FL.

Gallaher, R.N., C.O. Weldon, and J.G. Futral. 1975. An aluminum digester for plant and
soil analysis. Soil Crop Sci. Soc. Amer Proc. 39:803-806.

Gates, R.N., G.M. Hill, and G.W. Burton. 1999. Response of selected and unselected
bahiagrass populations to defoliation. Agron. J. 91:787-795.

Gates, R.N., C.L. Quarin, and C.G.S. Pedreira. 2004. Bahiagrass, In L. E. Moser et al.,
(eds.). Warm season (C4) grasses monograph. ASA/CSSA, Madison, WI. (in press).

George, J.R., G.S. Reigh, R.E. Mullen, and J.J. Hunczak. 1990. Switchgrass herbage and
seed yield and quality with partial spring defoliation. Crop Sci. 30:845-849.

Gerrish, J.R. 1991. Biological implications of rotational grazing. p. 6-9. Proc. Am.
Forage Grassl. Conf. In Proc. Am. Forage Grassl. Conf., Columbia, MO. 1-4 Apr.
1991. Am. Forage Grassl. Council, Georgetown, TX.

Hammond, C. 1994. Animal Waste and the Environment. Circular 827. Univ. of Ga.
Athens, GA.

Hammond, A.C., M.J. Williams, T.A. Olson, L.C. Gasbarre, E.A. Leighton, and M.A.
Menchaca. 1997. Effect of rotational vs. continuous intensive stocking of
bahiagrass on performance of Angus cows and calves and interaction with sire type
on gastrointestinal nematode burden. J. of Anim. Sci. 75:2291-2299.

Hernandez Garay, A., L.E. Sollenberger, D.C. McDonald, G.J. Ruegsegger, R.
Kalmbacher, and P. Mislevy. in review. Nitrogen fertilization and stocking rate
affect stargrass pasture and cattle performance.

Johnson, C.R., B.A. Reiling, P. Mislevy, and M.B. Hall. 2001. Effects of nitrogen
fertilization and harvest date on yield, digestibility, fiber, and protein fractions of
tropical grasses. J. Anim. Sci. 79:2439-2448.

Jones, C.A. 1985. Temperature. p. 140-149. In C.A. Jones (eds.) C4 grasses and cereals:
Growth, development, and stress response. John Wiley & Son, New York.

Lima, G.F.da C., L.E. Sollenberger, W. Kunkle, J.E. Moore, and A.C. Hammond. 1999.
Nitrogen fertilization and supplementation effects on performance of beef heifers
grazing limpograss. Crop Sci. 39:1853-158.

Lorenz, R.J., and G.A. Rogler. 1972. Forage production and botanical composition of
mixed prairie as influenced by nitrogen and phosphorus fertilization. Agron. J.
64:244-248.

Mathews, B.W., L.E. Sollenberger, and C.R. Staples. 1994. Dairy heifer and
bermudagrass pasture responses to rotational and continuous stocking. J. Dairy Sci.
77:244-252.









Matches, A.G. 1992. Plant response to grazing: A review. J. Prod. Agric. 5:1-7.

Mislevy, P. 1985. Forages for grazing systems in warm climates. p. 122-129. In L. R. M.
Dowell (ed.). Nutrition of grazing ruminants in warm climates. Academic Press,
Orlando, FL.

Mislevy, P., and W.F. Brown. 1991. Management and utilization of complementary
forages: Stargrass. 40th Florida Beef Cattle Short Course. Univ. of Fla., Gainesville.

Moore, J.E., and G.O. Mott. 1974. Recovery of residual organic matter from in vitro
digestion of forages. J. Dairy Sci. 57:1258-1259.

Mott, G.O., and H.L. Lucas. 1952. The design, conduct, and interpretation of grazing
trials on cultivated and improved pastures. p. 1380-1385. In Proc. Int. Grassl.
Congr., 6th, 17-23 Aug. 1952, State College, PA. Pennsylvania State Univ., State
College, PA.

Moyer, J.L., D.W. Sweeney, and R.E. Lamond. 1995. Response of tall fescue to fertilizer
placement at different levels of phosphorus, potassium, and soil pH. J. Plant Nut.
18:729-746.

Muchovej, R.M., and J.J. Mullahey. 2000. Yield and quality of five bahiagrass cultivars
in southwest Florida. Soil Crop Sci. Soc. Fla Proc. 59:82-84.

Muchovej, R.M., and J.E. Rechcigl. 1994. Imact of nitrogen fertilization of pastures and
turfgrasses on water quality. p. 91-135. In B.A. Stewart and R. Lal (eds.). Soil
processes and water quality. Lewis Publishers Inc., Boca Raton, FL.

Newman, Y.C., L.E. Sollenberger, and C.G. Chambliss. 2003. Canopy height effects on
vaseygrass and bermudagrass spread in limpograss pastures. Agron. J. 95:390-394.

Nichols, J.T., P.E. Reece, G.W. Hergert, and L.E. Moser. 1990. Yield and quality
response of subirrigated meadow vegetation to nitrogen, phosphorus and sulfur
fertilizer. Agron. J. 54:47-52.

Pitman, W.D., D.D. Redfearn, and J.C. Read. 2000. Response of Texas bluegrass to
season of nitrogen fertilization on the Louisiana Coastal Plain. J. Plant. Nut.
23:423-429.

Prates, E.R., H.L Chapman, Jr., E.M. Hodges, and J.E. Moore. 1975. Animal
performance by steers grazing 'Pensacola' bahiagrass pasture in relation to forage
production, forage composition, and estimated intake. Soil Crop Sci. Soc. Fla Proc.
34:152-155.

Prine, G.M., and G.W. Burton. 1956. The effect of nitrogen rate and clipping frequency
upon the yield, protein content and certain morphological characteristics of coastal
bermudagrass. Agron. J. 48:296-301.









Ruelke, O.C., and G.M. Prine. 1971. Performance of six hybrid bermudagrass, Pangola
digitgrass, and Pensacola bahiagrass at three fertility levels in north Central Florida.
Soil Crop Sci. Soc. Fla Proc. 31:67-71.

SAS Inst. Inc. 1996. SAS statistics user's guide. Release Version 6. SAS Inst. Inc., Cary,
NC.

Sinclair, T.R., J.D. Ray, P. Mislevy, and L.M. Premazzi. 2003. Growth of subtropical
forage grasses under extended photoperiod during short-daylength months. Crop
Sci. 43:618-623.

Sollenberger, L.E. 2001. Tropical legume and grass characteristics. Notes from AGR
6233, Univ. of Fla.

Sollenberger, L.E., G.F.da C. Lima, J.F. Holderbaum, W.E. Kunkle, J.E. Moore, and
A.C. Hammond. 1997. Cattle wight gain and sward-animal nitrogen relationships
in grazed Hemarthria altissima pastures. p. 43-44. In Proc. Int. Grassl. Congress,
18 Winnipeg, MB, and Saskatoon, SK, Canada. 8-17 June. Grasslands 2000,
Toronto.

Sollenberger, L.E., W.R. Ocumpaugh, V.P.B. Euclides, J.E. Moore, K.H. Quesenberry,
and C.S. Jones, Jr. 1988. Animal performance on continuously stocked Pensacola
bahiagrass and Floralta limpograss. J. Prod. Agric. 1:216-220.

Sollenberger, L.E., G.A. Rusland, C.S. Jones, Jr., K.A. Albrecht, and K.L. Gieger. 1989.
Animal and forage responses on rotationally grazed 'Floralta' limpograss and
'Pensacola' bahiagrass pastures. Agron. J. 81:760-764.

Springer, T.L., and C.M. Taliaferro. 2001. Nitrogen fertilization ofbuffalograss. Crop
Sci. 41:139-142.

Stanley, R. L., Jr. 1994. Resonse of 'Tifton 9' Pensacola bahiagrass to harvest interval and
nitrogen rate. Soil Crop Sci. Soc. Fla Proc. 53:80-81.

Stanley, R.L., E.R. Beaty, and J.D. Powell. 1977. Forage yield and percent cell wall
constituents of Pensacola bahiagrass as related to N fertilization and clipping
height. Agron. J. 69:501-504.

Sumner, S., W. Wade, J. Selph, J. Southwell, V. Hoge, P. Hogue, E. Jennings, P. Miller,
and T. Seawright. 1991. Fertilization of established bahiagrass pasture in Florida.
Univ. of FL Cir. 916.

Tharel, L.M. 1989. Rotational grazing on three bermudagrass cultivars. Special Report,
Ag. Exp. Stn., Univ. of Ark.:17-19.

Thom, W.O., H.B. Rice, M. Collins, and R.M. Morrison. 1990. Effect of applied fertilizer
on Tifton 44 bermudagrass. J. Prod. Agric. 3:498-501.









Twidwell, E., W.D. Pitman, and G.J. Cuomo. 1998. Bahiagrass production and
management. LSU publication # 2697.

Tyagi, G.D., and V. Singh. 1986. Effect of cutting management and nitrogen fertilization
on yield and quality ofPennisetumpedicellatum Trin. (Dinanath grass). Trop.
Agric. 63:121-124.

U.S. Census Bureau. 2002. State and County QuickFacts: Florida.
http://quickfacts.census.gov. 24 May, 2003.

Utley, P R, H.D. Chapman, W.G. Monson, W.H. Marchant ,and W.C. McCormick. 1974.
Coastcross-I bermuda grass, Coastal bermuda grass and Pensacola bahiagrass as
summer pasture for steers. J. Anim. Sci. 38: 490-495.

Velez-Santiago, J., and J.A. Arroyo-Aguilu. 1983. Nitrogen fertilization and cutting
frequency, yield and chemical composition of five tropical grasses. J. Agric. Univ.
Puerto Rico 67:61-69.

Wiedenfeld, R.P. 1988. Coastal bermudagrass and Renner lovegrass fertilization
responses in a subtropical climate. J. Range Mange. 41:7-11.

Williams, M.J., and A.C. Hammond. 1999. Rotational vs. continuous intensive stocking
management of bahiagrass pasture for cows and calves. Agron. J. 91:11-16.

Wilson, J.R. 1983. Effects of water stress on herbage quality. p. 470-472. In J.A. Smith
and V.W. Hays (eds.) Proc. Int. Grassl Cong, 14t. 15-24 June 1981, Lexington, KY

Zhang, Y., L.D. Bunting, L.C. Kappel, and J. Hafley. 1995. Influence of nitrogen
fertilization and defoliation frequency on nitrogen constituents and feeding value of
annual ryegrass. J. Anim. Sci. 72:2474-2482.















BIOGRAPHICAL SKETCH

R. Lawton Stewart, Jr. was born 29 June 1979, in Columbus, Mississippi, and

grew up in Tifton, Georgia. Lawton received a B.S. in animal and dairy science at the

University of Georgia. A member of Gamma Sigma Delta honor society, Lawton plans

to pursue a Doctor of Philosophy in animal science at Virginia Polytechnic Institute and

State University upon completion of his Master of Science in agronomy. At VPI, where

he is the recipient of the J.L. Pratt fellowship, Lawton plans to study ruminant nutrition.