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Harvest Management of Tifton 85 Bermudagrass

Permanent Link: http://ufdc.ufl.edu/UFE0041308/00001

Material Information

Title: Harvest Management of Tifton 85 Bermudagrass
Physical Description: 1 online resource (125 p.)
Language: english
Creator: Clavijo Michelangeli, Jose
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: bermudagrass, budget, dairy, defoliation, forage, greenchop, harvest, height, interval, management, stubble, tifton
Agronomy -- Dissertations, Academic -- UF
Genre: Agronomy thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Harvest management is critical in hay or greenchop systems to sustain high yields of superior nutritive value. Tifton 85 bermudagrass (Cynodon spp.) is a high-quality, high-yielding warm-season perennial grass that has stimulated interest among dairy producers for use as hay, silage, and pasture. Despite the increasing adoption of this grass and the potential for utilization in rations of lactating cows, harvest management practices and the economic implications of Tifton 85 as a component of rations have not been studied widely. Morphological features of this plant compared to other grasses used in the region suggest the adoption of a more conservative harvest stubble may be needed. During 2007 and 2008, a field study was conducted with the objective of determining the effects of harvest management of Tifton 85 on forage yields, nutritive value, and nutrient removal. A second objective was to examine the feasibility of incorporating Tifton 85 greenchop into lactating dairy cow diets. To meet the first objective, different harvest intervals (21, 24, 27, and 35 d) and stubble heights (8 and 16 cm) were compared using established Tifton 85 bermudagrass fields. Dry matter (DM) yield, nitrogen (N) and phosphorus (P) removal by the grass, and herbage concentrations of crude protein (CP), P, neutral detergent fiber (NDF) and in vitro digestible organic matter (IVDOM) were measured. To meet the second objective, a least-cost ration formulation linear program was developed using data from the field study. Results from the harvest management trial and least-cost ration formulation indicate that Tifton 85 can be included in diets of milking herds when appropriate management is used. The field trials suggest that highest yields occur with lower harvest intervals (35 d) when adequate moisture is present, and when shorter stubble heights (8 cm) are used. Nevertheless, shorter stubble heights (8 cm) were associated with greater weed encroachment and are generally not recommended. Also, management for greater nutritive value and stand persistence can be met generally with more frequent defoliation at 24- to 27-d intervals. When Tifton 85 greenchop was included in the ration formulation model and compared to other widely used forage options in the state, such as alfalfa (Medicago sativa L.) hay, Tifton 85 hay, and corn (Zea mays L.) silage, ration costs were reduced for a range of production levels of lactating dairy cows. Future research should use animal trials to estimate the impacts of incorporating greenchop on milk production, and the assessment of the economic impact of using Tifton 85 greenchop at the whole-farm level. Also, forage management trials incorporating the different harvest management treatments under different N fertilization rates and sources, and the impact on the environment should be considered.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jose Clavijo Michelangeli.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Newman, Yoana C.
Local: Co-adviser: Sollenberger, Lynn E.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0041308:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041308/00001

Material Information

Title: Harvest Management of Tifton 85 Bermudagrass
Physical Description: 1 online resource (125 p.)
Language: english
Creator: Clavijo Michelangeli, Jose
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: bermudagrass, budget, dairy, defoliation, forage, greenchop, harvest, height, interval, management, stubble, tifton
Agronomy -- Dissertations, Academic -- UF
Genre: Agronomy thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Harvest management is critical in hay or greenchop systems to sustain high yields of superior nutritive value. Tifton 85 bermudagrass (Cynodon spp.) is a high-quality, high-yielding warm-season perennial grass that has stimulated interest among dairy producers for use as hay, silage, and pasture. Despite the increasing adoption of this grass and the potential for utilization in rations of lactating cows, harvest management practices and the economic implications of Tifton 85 as a component of rations have not been studied widely. Morphological features of this plant compared to other grasses used in the region suggest the adoption of a more conservative harvest stubble may be needed. During 2007 and 2008, a field study was conducted with the objective of determining the effects of harvest management of Tifton 85 on forage yields, nutritive value, and nutrient removal. A second objective was to examine the feasibility of incorporating Tifton 85 greenchop into lactating dairy cow diets. To meet the first objective, different harvest intervals (21, 24, 27, and 35 d) and stubble heights (8 and 16 cm) were compared using established Tifton 85 bermudagrass fields. Dry matter (DM) yield, nitrogen (N) and phosphorus (P) removal by the grass, and herbage concentrations of crude protein (CP), P, neutral detergent fiber (NDF) and in vitro digestible organic matter (IVDOM) were measured. To meet the second objective, a least-cost ration formulation linear program was developed using data from the field study. Results from the harvest management trial and least-cost ration formulation indicate that Tifton 85 can be included in diets of milking herds when appropriate management is used. The field trials suggest that highest yields occur with lower harvest intervals (35 d) when adequate moisture is present, and when shorter stubble heights (8 cm) are used. Nevertheless, shorter stubble heights (8 cm) were associated with greater weed encroachment and are generally not recommended. Also, management for greater nutritive value and stand persistence can be met generally with more frequent defoliation at 24- to 27-d intervals. When Tifton 85 greenchop was included in the ration formulation model and compared to other widely used forage options in the state, such as alfalfa (Medicago sativa L.) hay, Tifton 85 hay, and corn (Zea mays L.) silage, ration costs were reduced for a range of production levels of lactating dairy cows. Future research should use animal trials to estimate the impacts of incorporating greenchop on milk production, and the assessment of the economic impact of using Tifton 85 greenchop at the whole-farm level. Also, forage management trials incorporating the different harvest management treatments under different N fertilization rates and sources, and the impact on the environment should be considered.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jose Clavijo Michelangeli.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Newman, Yoana C.
Local: Co-adviser: Sollenberger, Lynn E.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0041308:00001


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1 HARVEST MANAGEMENT OF TIFTON 85 BERMUDAGRASS By JOSE ALEJANDRO CLAVIJO MICHELANGELI 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 2009

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2 2009 Jos Alejandro Clavijo Michelangeli

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3 To Claret, Pepe Padre, Tati (my role model) and JP

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4 ACKNOWLEDGMENTS First of all, I would like to thank my parents, sister godmother and brother inlaw for their endless love, encouragement and constant support. They are my motivation and source of strength and joy I want to thank Dr. Yoana Newman, my committee chair, for her confidence in my possibilities as a graduate student and for making me a part of the Gator Nation. I also want to thank Dr. Leonardo Ortega for his insight, assistance, and especially for putting in his free time and weekends guiding my work. I also would like to acknowledge Drs. Sollenberger and Staples for their positive criticism, support and patience throughout my program, and for giving me the flexibility to pursue my interests at UF. Big t hanks go out to the extended Agronomy Department family: Paula, Theresa, Cynthia, Katie, Christina, Kim, Dr. Rose Koenig, Dr. Ken Buhr, Judy and Micah. They made my time at Newell Hall and Building 737 fun and very memorable. Thanks also go out to Richard Fethiere for his assistance in processing samples and for sharing his knowledge about history, sports and forage chemical analysis. I would like to acknowledge Drs. Jason Ferrell and Greg McDonald for their help in weed control and identification. This study was supported by a grant from the Florida Milk Check off. Special thanks go to Mr. Don Bennick, from North Florida Holsteins, and to Mr. Don Quincey, from Quincey Cattle Co., and their respective crews for facilitating the study sites. Their support, assistance and knowledge of the land and farming showed me how progressive farmers bring meat and milk to Floridians tables. I would also like to thank the good friends that made my time at UF an incredible experience I am very thankful to Dr. Peter H ildebrand for his mentorship, inspiration,

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5 and help developing the linear program model, but most importantly, for his friendship, guidance and knowledge that have led me to view agronomy from a different angle and to think about the broader implications of the work we do. Our many early morning meetings over coffee will st ay with me the rest of my life. Drs. Scott Robinson and Dave Steadman from the Florida Museum of Natural History gave me a second home on campus, treated me as one of their own, and allowed me to keep my passion for birds alive and well. I would also like to thank Dr. Howard Frank for his friendship and support in getting me to UF and throughout my program. Finally, big thanks go to Johnny, Nick, Martijn, Walid, Linda, and Marlene for enr iching my academic experience, and for being with me in the good and bad.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 8 ABSTRACT ................................................................................................................... 12 CHAPTER 1 INTRODUCTION .................................................................................................... 14 2 LITERATURE REVIEW .......................................................................................... 17 Tifton 85 Bermudagrass ........................................................................................ 17 Forage Responses to Defoliation ............................................................................ 19 Effects on dry matter yiel ds .............................................................................. 19 Effects on nutritive value .................................................................................. 21 Tifton 85 Bermudagrass Use as Harvested Forage ................................................ 24 Removal of Nutrients .............................................................................................. 26 Forage Budgets ...................................................................................................... 28 Dairy Manure Costs ................................................................................................ 30 Least Cost Ration Linear Programming Models for Dairy Cattle ............................ 32 3 HARVEST MANAGEMENT EFFECTS ON FORAGE DRY MATTER PRODUCTION AND NUTRIENT REMOVAL OF TIFTON 85 BERMUDAGRASS 34 Introduction ............................................................................................................. 34 Materials and Methods ............................................................................................ 36 Study site description ....................................................................................... 36 Harvest management and sampling ................................................................. 37 Experimental design ......................................................................................... 38 Data analysis .................................................................................................... 40 Results and Discussion ........................................................................................... 40 Weather conditions ........................................................................................... 40 Total DM yields ................................................................................................. 42 Seasonal (by harvest) DM yields ...................................................................... 44 Tifton 85 bermudagrass nutrient removal ......................................................... 48 Weed assessment ............................................................................................ 51 Summary and Conclusions ..................................................................................... 51 4 HARVEST MANAGEMENT EFFECTS OF TIFTON 85 BERMUDAGRASS ON HERBAGE NUTRITIVE VALUE .............................................................................. 54 Introduction ............................................................................................................. 54 Materials and Methods ............................................................................................ 55

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7 Study site description ....................................................................................... 55 Treatments ....................................................................................................... 55 Herbage sampling and processing ................................................................... 56 Laboratory analysis .......................................................................................... 56 Statistical analysis ............................................................................................ 56 Results and Discussion ........................................................................................... 57 Crude protein .................................................................................................... 57 Phosphorus ...................................................................................................... 59 In vitro digestible organic matter ....................................................................... 63 Neutral detergent fiber ...................................................................................... 67 Summary and Conclusions ..................................................................................... 67 5 ECONOMIC ANALYSIS OF TIFTON 85 GREENCHOP INCORPORATION INTO DAIRY RATIONS .......................................................................................... 70 Introduction ............................................................................................................. 70 Materials and Methods ............................................................................................ 71 Tifton 85 bermudagrass greenchop production cost ........................................ 71 Determination of machinery costs .................................................................... 73 Developing budgets based on results from agronomic trials ............................ 74 Calculation of manure and irrigation cost for forage production budget ........... 74 Least cost ration linear program model ............................................................ 75 Results and Discussion ........................................................................................... 80 Tifton 85 bermudagrass establishment budget ................................................. 80 Tifton 85 bermudagrass greenchop production budgets .................................. 81 Least cost linear program model results ........................................................... 83 Conclusions and Recommendations ...................................................................... 96 6 SUMMARY AND CONCLUSIONS .......................................................................... 99 APPENDIX: RESULTS OF LEAST COST RATIONS FORMULATED WITH TIFTON 85 BERMUDAGRASS GREENCHOP HARVESTED AT DIFFERENT HARVEST INTERVALS ........................................................................................ 104 LIST OF REFERENCES ............................................................................................. 114 BIOGRAPHICAL SKETCH .......................................................................................... 125

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8 LIST OF TABLES Table page 3 1 Current interpretation for Mehlich 1 soil test results for agronomic and vegetable crops. ................................................................................................. 37 3 2 Harvest schedule for Tifton 85 harvest intervals in 2007 and 2008. ................... 38 3 3 Observed significance level ( P value) from mixed models for the effects of harvest interval (HARVEST), stubble height (STUBBLE) and year on total DM yields (Mg DM ha1 ). ..................................................................................... 42 3 4 Comparison of DM yield means as affected by harvest interval (HARVEST) and stubble height (STUBBLE) in 2007 and 2008. ............................................. 43 3 5 Observed significance level ( P value) from mixed models of the effects of stubble height (STUBBLE) and harvest event (HE) on total DM yield analyzed by harvest interval (HARVEST) in 2007 and 2008. ............................. 44 3 6 Stubble height (STUBBLE) harvest event effects on DM yield analyzed by harvest interval (HARVEST) in 2007. ................................................................. 47 3 7 Stubble height (STUBBLE) harvest event effects on DM yield, analyzed by harvest interval (HARVEST) in 2008. ................................................................. 47 3 8 Observed significance level ( P value) from mixed models of the effects of harvest interval (HARVEST) and stubble height (STUBBLE) on total N and P removal, analyzed by ye ar. ................................................................................. 49 3 9 Yield, nutrient concentration, and nutrient removal of Tifton 85 bermudagrass in response to increasing harvest interval ( HARVEST ) and two stubble heights (STUBBLE) in 2007 and 2008. ............................................................... 49 4 1 Observed significance level ( P value) from mixed models of the effects of stubble height (STUBBLE) and harvest interval (HARVEST) on Tifton 85 herbage CP, P IVDOM and NDF concentrations in 2007and 2008. .................. 58 4 2 Comparison of total (year) herbage crude protein (CP) and phosphorous (P) me ans as affected by harvest interval (HARVEST) for 2007 and 2008. ............. 60 4 3 Comparison of total (year) in vitro digestible organic matter (IVDOM) means as affected by the stubble height harvest interval interaction. ......................... 64 5 1 Nutritional requirements of lactating Holstein dairy cows used in linear program model ................................................................................................... 77 5 2 Selected constraint levels utilized in linear program model. ............................... 78

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9 5 3 Pr ices of readily available feedstuffs to dairy producers in Florida ..................... 79 5 4 Establishment budget for Tifton 85 bermudagrass using vegetative tops. .......... 8 2 5 5 Production costs of Tifton 85 bermudagrass greenchop with 3 harvests per season (35 d interval) and dairy manure as fertilizer source during 2007. ......... 84 5 6 Cost of DM, crude protein and net energy for lactation using T85 greenchop with 3 harv ests per season (35d harvest interval) during 2007. ........................ 84 5 7 Production costs of Tifton 85 bermudagrass greenchop with 4 harvests per season (24and 27d interval) and dairy manure as fertilizer source during 2007. .................................................................................................................. 85 5 8 Cost of DM, crude protein and net energy for lactation using T85 greenchop with 4 harvests per season (24and 27 d harvest interval) during 2007. ........... 85 5 9 Production costs o f Tifton 85 bermudagrass greenchop with 5 harvests per season (21d interval) and dairy manure as fertilizer source during 2007. ......... 86 5 10 Cost of DM, crude protein and net energy for lactation using T85 greenchop with 5 harvests per season (21d harvest interval) during 2007. ........................ 86 5 11 Production budget for Tifton 85 bermudagrass greenchop with 3 harvests per season (35d harvest interval) during 2008. ....................................................... 87 5 12 Cost of DM, crude protein and net energy for lactation using T85 greenchop with 3 harvests per season (35d harvest interval) during 2008. ........................ 87 5 13 Production budget for Tifton 85 bermudagrass greenchop with 4 harvests per season (24and 27d harvest intervals) during 2008. ........................................ 88 5 14 Cost of DM, crude protein and net energy for lactation using T85 greenchop with 4 harvests per season (24and 27 d harvest interval) during 2008. ........... 88 5 15 Production budget for Tifton 85 bermudagrass greenchop with 5 harvests (21 d interval) per season during 2008. .............................................................. 89 5 16 Cost of DM, crude protein and net energy for lactation using T85 greenchop with 5 harvests per season (21d harvest interval) during 2008. ........................ 89 5 17 Relevant information from Tifton 85 greenchop field trials and production cost. .................................................................................................................... 90 5 18 Average cost of daily rations for lactating dairy cows grouped by production level formulated with different forages. ............................................................... 91 5 19 Average cost of forage DM, crude protein and net energy (NEL) for lactation in purchased forages and T85 greenchop treatments. ....................................... 92

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10 5 20 Ration costs of least cost linear program model using Tifton 85 greenchop harvested in 2007 and 2008 growing seasons. .................................................. 94 5 21 Ration profile and costs of least cost linear program model using Tifton 85 greenchop harvested in 2008 for selected cow profiles. ..................................... 96 A 1 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested at 21d intervals (2007). ................................ 104 A 2 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 24d intervals ( 2007) ..................................... 105 A 3 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 27d inter vals (2007) ..................................... 106 A 4 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 35d intervals (2007). .................................... 107 A 5 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harves ted 21d intervals (2008). .................................... 108 A 6 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 24d intervals (2008). .................................... 109 A 7 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 27d intervals (2008). .................................... 110 A 8 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 35d intervals (2008). .................................... 111 A 9 Ingredients and costs of rations formulated for selected lactating dai ry cows using alfalfa hay. ............................................................................................... 112 A 10 Ingredients and costs of rations formulated for selected lactating dairy cows using purchased T ifton 85 hay. ......................................................................... 113

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11 LIST OF FIGURES Figure page 3 1 Experimental layout of defoliation management trial during 2007 and 2008. ..... 39 3 2 Monthly rainfall for the study site in 2007 near Bell, Florida and for the study site in 2008 near Chiefland, FL. .......................................................................... 41 3 3 Dry matter yield response of Tifton 85 bermudagrass to harvest event by harvest interval (HARVES T) in 2007. ................................................................. 45 3 4 Dry matter yield response of Tifton 85 bermudagrass to harvest event by harvest interval (HARVEST) interaction in 2008. ................................................ 46 4 1 Crude protein (CP) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2007. ........................................................................... 61 4 2 Crude protein (CP) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2008.. .......................................................................... 62 4 3 In vitro digestible organic matter (IVDOM) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2007. .................... 65 4 4 In vitro digestible organic matter (IVDOM) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2008. .................... 66

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12 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 HARVEST MANAGEMENT OF TIFTON 85 BERMUDAGRASS By Jos Alejandro Clavijo Michelangeli December 2009 Chair: Yoana C. Newman Major: Agronomy Harvest management is critical in hay or greenchop systems to sustain high yields of superior nutritive value. Tifton 85 bermudagrass ( Cynodon spp.) is a highquality, high yielding warm season perennial grass that has stimulated interest among dairy producers for use as hay, silage and pasture. Despite the increasing adoption of this grass and the potential for utilization in rations of lactating cows, harvest management practices and the economic implications of Tifton 85 as a component of rations have not been studied widely. Morphological features of this plant compared to other grasses used in the region sug gest the adoption of a more conservative harvest stubble may be needed. During 2007 and 2008, a field study was conducted with the objective of determining the effects of harvest management of Tifton 85 on forage yields nutritive value, and nutrient removal A second objective was to examine the feasibility of incorporating Tifton 85 greenchop into lactating dairy cow diets T o meet the first objective, different harvest in t ervals (21, 24, 27, and 35 d ) and stubble heights (8 and 16 cm) were compared using established Tifton 85 bermudagrass fields. D ry matter (DM) yield, nitrogen ( N ) and phosphorus ( P ) removal by the grass, and herbage concentrations of crude protein (CP), P neutral detergent fiber (NDF) and in vitro

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13 digestible organic matter (IVDOM) were measured. To meet the second objective, a least cost ration formulation linear program was developed using data from the field study Results from the harvest management trial and least cost ration formulation indicate that Tifton 85 can be included in diets of milking herds when appropriate management is used. The field trials suggest that highest yields occur with lower harvest intervals (35 d) when adequate moisture is present, and when shorter stubble heights (8 cm) are used. Nevertheless, shorter stubble heights ( 8 cm ) were associated with greater weed encroachment and are generally not recommended. Also, management for greater nutri tive value and stand persistence can be met generally with more frequent defoliation at 24to 27d intervals. When Tifton 85 greenchop was included in the ration formulation model and compared to other widely used forage options in the state, such as alfalfa ( Medicago sativa L.) hay, Tifton 85 hay, and corn ( Zea mays L.) silage, ration costs were reduced for a range of production levels of lactating dairy cows. Future research should use animal trials to estimate the impacts of incorporating greenchop on milk production, and the assessment of the economic impact of using Tifton 85 greenchop at the wholefarm level. Also, forage management trials incorporating the different harvest management treatments under different N fertilization rates and sources, and the impact on the environment should be considered.

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14 CHAPTER 1 INTRODUCTION Recent estimate s indicate that over 68% of all agricultural lands in the USA are used for forage production, as rangeland, planted pasture, or for mechanical harvest (USDA NASS, 2 009 ). Grasslands sustain the livestock industry and are one of the most important land uses in the country Forage production is pi votal for Floridas agriculture and economy. For example, in 2007 alone, beef and dairy farming generated more than $900 mill ion in cash receipts (USDA NASS, 2009b). These industries rely heavily on the 2 .1 million ha of pastureland in the state, of which more than 300,000 ha are planted forages for mechanical harvest (USDA NASS, 2009b). The prominence of grassland agriculture emphasizes the importance of developing forages and management practices adapted to Florida farming conditions. Of the forage species grown in the state, warm season perennial grasses provide the basis for livestock production (Pitman, 2007). Among the spec ies planted, hybrid bermudagrasses have a prominent role because of their adaptability to grazing and mechanical harvest, high yields, and quality (Chambliss et al., 2006). Among the bermudagrasses developed, Tifton 85 bermudagrass has gained acceptance si nce its release in 1993 throughout the southern USA and particularly in Florida as harvested forage and in grazing systems (Hill et al., 2001). Additionally, it has shown potential in excess nutrient removal from effluent sprayfields (Newton et al., 2003; Woodard et al., 2003, 2007) becoming a preferred option for soil nutrient management in intensive animal feeding operations. Forage research results suggest that Tifton 85 can be used as a source of digestible fiber to supplement high energy diets for lactating dairy cows when harvested

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15 at early growth stages (West et al., 1998) Because of the lower costs associated with using local or on farm grown forage (Hill et al., 2001) use of Tifton 85 may be a viable alternative to using alfalfa (West et al., 19 97) or corn silage (Mandebvu et al., 1998) in dairy animal rations Although its benefits in grazing, silage, and hay production are known, further research is needed to assess its potential use as greenchop in confined dairy systems. Greenchop is a management practice where the aboveground biomass of the forage is mechanicall y harvested and fed fresh to livestock; an approach that avoids the problems of hay making in humid environments. In order for producers to take advantage of the potential of bermudag rasses for use as harvested forage or in nutrient extraction from soil management practices must be tailored to specific environmental and farming conditions. Among these practices, management of defoliation is perhaps one of the most important aspects th at producers control, because of its marked effects on yield, nutritive value, and stand persistence. In general for bermudagrasses, longer harvest intervals tend to maximize dry matter yields but decrease herbage nutritive value (Monson and Burton, 1982; Holt and Conrad, 1986; Johnson et al., 2001; Burns and Fisher, 2007), whereas more intensive defoliation increases yields but can compromise persistence over multiple seasons (Mislevy and Everett, 1981). Thus, it is important to understand the effects of h arvest interval and stubble height on yields and nutritive value of bermudagrasses, and to evaluate the economic feasibility of different forage utilization alternatives in order to generate specific management guidelines for producers in the Southeast USA The objectives of this study were to quantify the effects of varying harvest interval and stubble height on dry matter yield, nutritive value, and N and P removal of Tifton 85

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16 bermudagrass, and to estimate the impact of incorporating Tifton 85 greenchop on cost of lactating dairy cow rations. The research can provide valuable information to producers about harvest management of Tifton 85 under Florida conditions, as well as provide insight into its potential use as greenchop for milking herd rations.

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17 C HAPTER 2 LITERATURE REVIEW Tifton 85 Bermudagrass Bermudagrass [ Cynodon dactylon (L.) Pers. ] is a tropical, stoloniferous forage plant native to tropical east Africa that has naturalized throughout the tropics and subtropics and is one of the most widespread and widely used genera of grasses in the world (Hanna and Sollenberger, 2007). This warm season perennial grass is used for hay production and grazing in the sout hern USA because of its high biomass production, rapid establishmen t and tolerance to defoliation and drought (Hill et al., 2001; Redfearn and Nelson, 2003). Currently, it is planted on approximately 15 million hectares in the USA ( Taliaferro et al., 2004). There are several cultivars of bermudagrass. They range from the low producing common to the high yielding and high quality hybrids (Hill et al., 2001). Among the many hybrid bermudagrasses developed and released in the southeastern USA Tifton 85 is one of the most recent (Burton et al., 1993). Others include Coastal bermudagrass, the first release d for use in southern forage programs (Burton, 1986), Tifton 44, one of the most coldtolerant hybrids (Monson and Burton, 1982), and several others such as Callie, Tifton 78, Florakirk, Coast Cross I, and Coast Cross II. The high nutritive value and upright growth habit characteristic of Tifton 85 can be attributed to its lineage This grass is the result of a cross between a tall, highly digestible African stargrass ( Tifton 68 ; C. nlemfuensis hybrid) and an armyworm resistant bermudagrass accession from South Africa ( PI 290884; C. dactylon ) (Burton, 2001). Morphologically, Tifton 85 is taller, has a more erect growth habit, thicker stems and stolons and wider leaves than previous bermudagrass releases It a lso produces

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18 larger but fewer rhizomes than Coastal bermudagrass (Burton et al., 1993). T ogether with the robust growth, these morphological traits have important implications in determining the defoliation management for long term persistence of Tifton 85. In addition, i t has shown greater drought tolerance (Marsalis et al., 2007) and lateseason dry matter (DM) production (Evers et al., 2004) than other hybrid or seeded bermudagrasses ; and while it is less cold tolerant than Tifton 44 bermudagrass, successful stands have been maintained as far north as North Carolina (Burns and Fisher, 2007). Sexual seed production is minimal, and like most hybrids, propagation is through vegetative material as stolons or rhizomes (Hill et al., 2001). Since its rele ase in 1993, Tifton 85 has gained acceptance throughout the southern USA as harvested forage (Hill et al., 2001). This plant showed promise in its initial small plot tria ls, producing 20, 19, and 22% more DM ha1 than Coastal, Tifton 44 and Tifton 68, resp ectively (Burton et al., 1993). More recently DM yields of Tifton 85 have been reported in the 16 to 26 Mg ha1 yr1T he high nutritive value of Tifton 85 has be en demonstrated in multiple studies throughout the S outheast USA (Hill et al., 2001; Mandebvu et al., 1999; Mislevy and Martin, 2006). The crude protein (CP) concentrations of this grass are greater than most tropical grasses grown in the region (Mislevy and Martin, 2006; Johnson et al., 2001; Marsalis et al., 2007), frequently exceeding 160 g kg range (Woodard et al., 2007; Marsalis et al., 2007).Yields of this magnitude have been associated with removal of large quantities of nutri ents from effluent sprayfields (Newton et al., 2003; Woodard et al., 2003, 2007) and Tifton 85 is considered an attractive option for good soi l nutrient management in animal feeding operations in the Southeast. 1. Likewise, the digestibility is

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19 considered better when compared to other warm or cool season forages used throughout Florida. Although Tifton 85 has a high fiber concentration like most tropical grasses, neutral detergent fiber (NDF) digestibility is greater than most of the warm season grasses grown in the region. It is this attribute that makes Tifton 85 a viable option for lactating dairy cow rations (Mandebvu et al., 1999; Mandebvu et al., 1998; West et al., 1997). Forage Responses to D efoliation Defoliation has marked effects on the physiological and morphological processes that occur in plants. In the short term, forages rely on mechanisms such as increased photosynthate allocation to shoots over roots (Nelson, 2000) and remobilization of stored C and N to sites of active photosynthesis and growth in order to rapidly reestablish the photosynthetic area of the plant (Tho rnton et al., 2000). Some forage species also can increase the photosynthetic ability of the leaves that remain on the plant after defoliation, a process known as compensatory photosynthesis (Richards, 1993). P lants also can modify their morphology in order to both reduce the probability of future defoliation events and to better withstand them as they occur. This is accomplished in certain species by altering leaf growth, rate of tillering and orientation of tillers and leaves in positions that are less l ikely to be harvested, i.e. favoring horizontal and lower growth (Nelson, 2000). Effects on dry matter yields Early studies on Coastal bermudagrass (Ethredge et al., 1973) suggest that both harvest interval and stubble height are important criteria to consider in hybrid bermudagrass management. These studies point to effects not only in terms of biomass

PAGE 20

20 production and leaf to stem ratios, but also to their effects on stand persistence throughout subsequent growing seasons. One of the early studies that l ooked at the effects of harvest interval is that of Prine and Burton (1956). The authors reported that increasing harvest interval increased cumulative DM yield over 70% from 5 .1 Mg ha1 at 14 d to 8.7 Mg ha1In another study Holt and Lancaster (1968) focused on the effects of stubble height on N fertilized Coastal bermudagrass. They found that defoliating to a 5cm stubble height and harvesting when the canopy was 35to 40cm tall produced DM yields of 15.3 Mg ha at 42 d, but this reduced leaf percentage fro m 86 to 63%. A study conducted in Puerto Rico by CaroCostas et al. (1972) on stargrass ( Cynodon nlemfuensis Vanderyst ) also reported that increasing harvest interval from 30 to 90 d increased DM yield, but no reduction in the leaf to stem ratio was detected. 1; the highest observed in the trial The authors noted that grass managed under tall stubble heights ( 13 cm ) had greater root mass accumulation than those under the shor t stubble ( 5 cm ) regime. They also found that more infrequent harvest treatments resulted in lower stand densities compared to those under more frequent cutting. Holt and Conrad (1986) evaluating various clipping treatments reported that total annual forag e yield of Coastal increased 0.15 Mg ha1 for each day that harvest was delayed after 14 d of regrowth Forage yield was 58% greater when harvested every 56 d than when harvested every 14 d. Ethredge et al. (1973) found that both harvest interval and stubble height had a major influence on Coastal DM yields, noting that shorter cutting heights (0 cm) resulted in greater DM yield than taller stubble (14 cm) (9.6 vs 6.5 Mg ha1 for 0 and 14 cm, respectively) Likewise, they found that

PAGE 21

21 longer harvest int ervals resulted in the highest annual DM yields (6.9 vs 8.2 Mg ha1More recent findings confirm the tr ends observed in earlier research Studies in the s outhern Piedmont on vegetatively propagated Midland 99 and Tifton 44 bermudagrasses show ed that under adequate moisture, harvest intervals of 4 and 6 wk maximized DM yields o n clay loam and sandy soils, respectively (Fike et al., 2005). Similar results also were obtained by Mandebvu et al. (1999), who found that longer harvest intervals (49 and 56 d) maximized Tifton 85 and Coastal bermudagrass yields, producing on average 6 and 6.4 Mg ha for 21and 35 d intervals, respectively). 1In summary, t hese studies found that harvest interval and stubble height are important parameters to consider in perennial hybrid bermudagrass management. In general, both short stubble heights and fewer harvests tend to increase DM yield. respectively. Effects on nutritive value Broadly defined, digestibility is a measure within forage nutritive value that represents the proportion of a feeds DM or of one of its constituents that is broken down and absorbed within the digestive tract of an animal (Barnes et al., 2007). In general its value is tightly linked to the chemical composition of the plant mat erial (Smith et al., 1972), to the structure of the forage in terms of plant architecture and leaf to stem ratios, the proportion of tissues (e.g. vascular bundles, mesophyll, and epidermis), and fiber fractions (Van Soest, 1967). Tropical grass canopies are generally vertically heterogeneous in terms of DM distribution and nutritive value, with nutrient concentrations and digestibility typically declining from the top of the canopy to soil level ( Stobbs, 1975 ; Newman et al., 2002). Because of the strong r elationship between digestibility and the morphological and physiological characteristics of forage plants, the

PAGE 22

22 effects of defoliation practices on digestibility have been an important area of study within bermudagrass management In the following, several studies are described that looked at the effect of harvest interval and stubble height on nutritive value. Early s tudies on Coastal bermudagrass found that in creasing harvest interval negatively affected DM digestibility percentages, with values decreasing from 65.2 to 56.6% as interval between defoliation increased from 21 to 42 d (Burton et al., 1963). This change was associated in part with a decrease in leaf percentage from 85.2 to 67.2% during the same interval. Holt and Conrad (1986) compar ed five bermudagrass cultivars (Coastal, Callie, Tifton 68, S 16, and S 83 ) harvested at 1 4 28 42 and 56d intervals and cut to a 5cm stubble. They found that digestibility declined as harvest interval increased, but that differences existed among t he rates at which this occurred among the species studied. Overall, the rate of decline in forage in vitro digestible dry matter (IVDDM), averaged across species, was 2 g kg1 of DM for each day of increasing age between 14 and 56 d. During this period, leafiness also declined by 180 g kg1, suggesting that the leaf to stem ratio can be an important factor that affects forage digestibility. Caro Costas et al. (1972) found that increasing harvest interval o f stargrass after 30 days at 15day intervals reduced forage digestibility; increasing lignin concentration from 7.8 to 10%. The researchers also reported a drop in herbage CP concentration from 146 to 77 g kg1 when interval between harvest s increased from 30 to 90 d (Caro Costas et al., 1972). Another study on Coastal bermudagrass harvest interval also found that CP concentration decreased with longer intervals between harvests averaging 18.25% at 14 d and decreasing to 12.03% at 42 d across different N fertilization rates (Prine and Burton, 1956).

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23 Res earch focus ing on comparing harvesting intervals of Tifton 85 hays also found that CP concentration dec lined markedly from 20.8% at 14 d of regrowth to 11.1% at 49 d, reflecting the lower leaf to stem ratios (Mandebvu et al., 1999). Mandebvu et al. (1998) also sho wed that delaying harvest by 25 d, from 24 to 49 d, produced a 43% decline in CP concentration in Tifton 85 hay More recent work focused on shorter harvest intervals ( 2 and 4 wk) at each of three N fertilization levels (0, 40, and 80 kg ha 1Specifically for Tifton 85, reports from Mandebvu et al (1998) show ed that when h arvested at 7 wk of regrowth the grass had a marked reductio n in digestibility of DM (IVDMD) a nd NDF at 48 h of fermentation when compared to forage harvested at 3.5 wk (from 58.5 to 50.9% and 53.5 to 38%, respectively). In the study, the authors also found that the 3.5wk treatment had similar IVDMD and greater NDF digestibility coefficients at 48 h than corn silage, a high quality forage component of cattle rations. Similar results were obtained by Mandebvu et al. (1999), who found that Tifton 85 harvested as hay at 3wk intervals had greater IVDMD, NDF digestibility and ADF digestibility than hays harvested at 5or 7 wk inter v a ls In this study, Tifton 85 was compared to Coastal bermudagrass harvested at similar ages. Tifton 85 had greater NDF concentrations but showed greater overall IVDMD (63.2 vs. 59.4%) and NDF digestibility (65.5 vs 57.8%). The reasons for this high digestibility in spite of high NDF in each 4wk period) (Vendramini et al., 2008). They concluded that management practices, such as shorter regrowth periods between harvests of Tifton 85 bermudagrass can be effective in increasing herbage CP concentration. I n their study CP was always gre ater for herbage harvested at 2wk intervals, obtaining an average of ~17 % compared to ~ 12% at 4wk intervals

PAGE 24

24 concentrations h as been related to the lower ether linked ferulic acid concentrations in Tifton 85 when compared to other f orages, a factor which appears to facilitate digestion by rumen microorganisms (Mandebvu et al., 1998b ). Given that longer intervals between harvests have negative effects on CP and IVDOM, management should target shorter intervals, as nutritive value appears to decrease markedly after 30 to 35 d of regrowth. This management should be considered particularly when feeding forages to ruminants such as lactating cows which require greater amounts of degradable nutrients Relative to the effect of stubble height on nutritive value, early studies conducted in Puerto Rico focused on the effects of stubble height on nutritive value for different warm season perennials. Comparisons of low (08 cm) or high (1825 cm) cutting heights for elephantgrass ( Penniset um purpureum ), guineagrass ( Panicum maximum ), Pangola digitgrass ( Digitaria eriantha), molassesgrass ( Melinis minutiflora ) or Caribgrass ( Eriochloa polystachya ) found no differences in forage CP concentration (Caro Costas and Vicente Chandler, 1961). Sim ilar results were obtained for stargrass under similar tropical conditions, where no differences in CP conce ntration were detected between 5 and 15 cm stubble heights (Caro Costas et al., 1972). Tifton 85 Bermudagrass Use as Harvested F orage The use of Tifton 85 bermudagrass as hay or silage has been documented widely for different livestock systems throughout the USA, but its use as greenchop has not been studied widely. Greenchop or fresh cut forage is a management practice where the aboveg round biomass of the forage is harvested mechanically and supplied directly to livestock. This approach avoids trampling and fouling (Marten and Donker, 1964) potential uprooting and spatial selectivity associated with grazing ( Weir and Torell,

PAGE 25

25 1959), an d provides an alternative to haying, particularly in environments where rain distribution in the summer is an important factor associated with nutrient loss (Scarbrough et al., 2005). Early studies in the southern US A compared milk production and forage and land utilization of fresh cut and grazing systems. Stone (1959 ) concluded that cows fed greenchop produced at least as much milk as cows under either strip or rotational grazing, while gaining more weight than cows under either pasture system. Additionally, this system appeared to reduce forage losses associated with trampling and uneven grazing pressure in pastures. Also this practice allowed producers to use lands that were farther away within their farms that would be unfeasible under grazing. While this work was done over 50 y ear s ago u nder less intensive farming systems than the ones currently used in Florida, the benefits of using greenchop appear relevant today when producers are forced to find alternative for age management strategies to produce high quality forages to meet the requirements of the herds. Bermudagrasses in general are well suited for mechanical harvest, given their high yield, rapid regrowth, and high nutritive value under frequent harvest (Tal iaferro et al., 2004). Studies have shown that Tifton 85 hay or silage can be used as a source of digestible fiber in high energy diets for lactating cows (West et al., 1998; Mandebvu et al., 1999), and that its high nutritive value and yields make it a vi able alternative to other harvested forages. Early studies that used Tifton 85 bermudagrass as silage found that material harvested at 5 wk could be an economically feasible substitute to using corn silage, given its lower costs of incorporation to the dai ry cow rations and its high NDF digestibility ( Ruiz et al., 1995). Additionally, in a study comparing dairy rations with

PAGE 26

26 Tift on 85 (harvested at 3.5wk) or a lfalfa hays, CP concentrations were similar (16.6 vs. 17.3%, respectively), but the NDF digestibili ty was considerably greater for diets containing Tifton 85 (ranging from 58.4 vs. 39.1%, res pectively), resulting in equal dry matter i ntake (DMI) of lactating Holstein cows (West et al., 1997). When compared with Coastal bermudagrass at different harvest ages (3, 4, 5, 6, 7, and 8 wk), Tifton 85 produced 7.1% more DM (4, 500 vs 4 200 kg ha1Similar results were obtained when comparing Alicia bermudagrass with Tifton 85, where hays harvested at 5 and 7 wk from fields receiving poultry litt er (18 t ha ), had significantly greater IVDMD (58.7 vs 54.8%), and had greater NDF digestib ility (55.7 vs. 48% ) and ADF digestibility (41.4 vs. 32.5%). These values show 9% great er DM digestion and 13.3% greater NDF digesti bility for Tifton 85 than Coastal (Mandebvu et al., 1999). 1) and commercial fertilizer (269 kg ha1 of N and 56 kg K2O ha1) (Hill et al., 2001). The authors reported that CP, ADF and NDF were similar among species but IVDMD was greater for Tifton 85 samples at both growth stages (Hill et al., 2001). When compared to s targrass in South Florida, Tifton 85 forage had similar CP (10.2 vs. 10%) and 11.9% greater IVDOM when both were harvested at 4 wk, without receiving fertilization throughout the experiment (Arthington and Brow n, 2005). These results suggest that Tifton 85 bermudagrass is a premium forage relative to other C4Removal of N utrients grasses, and that it can be ado pted for highquality hay production. T he use of forage production in effluent sprayfields can help r educe potential nutrient leaching (Rotz et al., 2002; Pant et al., 2004). Under Florida conditions, C4 grasses managed intensively can be effective options for removal of soil nutrients, particularly N (Woodard et al., 2002) and P (Newman et al., 2009; New man et al.,

PAGE 27

27 2009b). Among the forages available, Tifton 85 has shown promise for use in soil nutrient remediation from impacted sites throughout the Southeast USA. M ultiforage cropping systems that contained Tifton 85 extracted 86% of applied N during the cropping season, which was greater than those based on warm season annuals ( Woodard et al., 2002). Studies in northern Florida suggest that systems based on this forage are appropriate for dairy sprayfields since they extract large amounts of N from the s oils, in addition to producing highyield s of forage with high CP concentration (Macoon et al., 2002). Modeling of N orth Florida farms, where crop models were run for 43 y ear s of daily weather data, also suggest that forage systems containing bermudagrass were among the best options for reducing N leaching (Cabrera et al., 2006). Woodard et al. (2003) studied cornbermudagrass rye ( Secale cereale L.) and corn rhizoma peanut ( Arachis glabrata Benth.) r ye forage rotations, and determined that for N removal, t he system containing Tifton 85 bermudagrass had the lowest NO3N levels and highest N harvest (191 kg ha1Woodard et al. (2007) determined that Tifton 85 was the best warm season component of year round forage systems in N orth Florida dairies for P extraction, with high P removal (67 kg ha ), despite a sustained decline in production after the first of three cycles. 1) a ssociated with high yields (3,800 kg ha1) However previous work (Woodard et al., 2003) found that stand persistence can decline co nsiderably in intensive year round forage systems possibly because of water, nutrient, and light competition issues with the other components of the rotation (i.e., corn and rye).

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28 After reviewing the literature, an important conclusion from these studies is that DM yield nutritive value, and nutrient removal cannot be maximized simultaneously by manipulating harvest interval requiring a compromise between them under any management situation. Given that the responses of forages to defoliation are expresse d differently at different time periods and affect various physiological and morphological processes, it is important to study how warm season grass species perform under different defoliation regimes, and how defoliation affects yield, herbage nutritive v alue, and soil nutrient removal. Understanding these processes can guide the development of forage management practices that fit the ecological and farming conditions of producers in the region, and allow for alternative forage uses to be evaluated for their economic feasibility. F orage Budgets B udgets are the financial layout for a given enterprise, with which the feasibility of alternative production technologies and management practices can be evaluated, aiding the decisionmaking process for resource u se optimization (Olson, 2004). B udgeting options exist that allow producer s to analyze different components and aspects of their businesses, from the wholefarm scale to specific farming activities Enterprise or unit budgets are projections of income and expenses that specify the quantities, price s, and relationships for a given meaningful unit of production, such as a hectare of pasture (James and Eberle, 2000) ; allowing farmers to plan ahead and gain insight into the potential economic outcomes of specif ic activities. Also, by conducting the analysis on a unit (i.e. per hectare) basis, the input use efficiency can be es timated more accurately than if total farm budgets are used (Olson, 2004).

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29 The use of forage budgets is a practice that managers and uni versity extension specialists use throughout the country, providing a framework to estimate the costs and profitability of a given forage production system and greatly enhancing the decisionmaking process of choosing the best cropping alternative or farm management practices (Schuler, 2005; Pflueger, 2005; Miller et al., 2003; Landblom et al., 2005). As with other financial instruments, budgeting strongly depends on using accurate and adequately classified information about the proposed enterprise (Kay et al., 2004). The data used to create these budgets can be placed into two broadly defined categories t hose relating to the physical relationships of transforming materials into products, or input output relationships, and those that refer to the prices of these inputs and outputs (James and Eberle, 2000). When arranging a cost structure, operational (variable) and ownership (fixed) costs need to be considered. Operational costs are those that occur only if production takes place, and vary with the volume o f production during the time period for which the budget is developed. Most forage budgets include fertilizer, agrochemicals (herbicide, insecticide), costs of vegetative establishment (propagating material and incorporation), machinery and labor costs, as well as the price of land rent. In turn, ownership costs refer to those that do not vary during the given time period of the study, even if no production takes place (Simpson, 1989; Kay et al., 2004), and would typically include depreciation, insurance, i nterests and housing costs of machinery and equipment, as well as taxes and other administrative costs (Olson, 2004; AAA E 2000). Because of the large amounts of manure that are generated in confinedhousing dairy farms, it is also important to consider it s potential

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30 use as a nutrient source for forage crops, and thus, analyze the economic impact of its management. Dairy Manure Costs Traditionally, manure has been considered a valuable resource in agricultural systems as a byproduct that has use as fertiliz er for crops (Keplinger and Hauck, 2006). On the other hand, the rapid decline in overall farm numbers in recent decades, accompanied by an increase in operation specialization and size, and the advent of relatively inexpensive synthetic fertilizers and st ricter environmental regulations has led to the increasing view of manure as an undesired waste product (Ribaudo et al., 2003; Keplinger and Hauck, 2006). This situation has forced farmers to pay close attention to all aspects of manure management, from animal nutrition and feeding strategies to handling, application, and cost estimation. Although the value of manure has decreased with time, particularly in relation to commercial fertilizers, it is still widely considered an important source of crop nutrients in many livestock centered farms, including dairy enterprises. Utilization of dairy manures generated on farm for forage production is one such example where producers, particularly in the Southeast, have taken advantage of the availability of this by p roduct in fertilization regimes. This approach reduces the potential leaching of excess N and P (MEQB, 2002; Rotz et al., 2002), and can provide significant amounts of forage that can help reduce feeding costs and nutrient imports into the system (Pant et al., 2004) Although the application of manures for forage production is viewed frequently simply as taking advantage of a waste product (Keplinger and Hauck, 2006), the incurred costs must be incorporated into farm budgets in order to adequately estimate

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31 the economic impact of their utilization in milk production systems (Ribaudo and Agapoff, 2005). Intrinsic characteristics of dairy excreta make their usage for crops more difficult and in some aspects more costly than traditional fertilizers. The low mas s:value ratios of manure markedly increases its handling, transportation and application costs when compared to typical purchased fertilizer (Keplinger and Hauck, 2006). Additionally, use of manure at agronomic rates is complicated by the fact that the ma nure nutrients occur in proportions that do not match crop requirements (Feinerman et al., 2004). Applications based on plant N requirements typically result in a buildup of P (Toth et al., 2006), given the difference in N : P ratios between those found in plant tissue (generally in the 56:1 range) and those supplied by livestock manure (typically approaching 2:1) (Toth et al. 2006; Dou et al., 2002; Elliot et al., 2002). Thus, applications based on plant N requirements may have negative environmental impact s, while those done based on P requirements typically require larger amounts of land for disposal of all farm generated wastes (particularly in operations with high animal densities) and frequently result in insufficient N being applied. Overall, any anal ysis of the fertilizer value of manure depends critically on assumptions about the concentration of N, P and K in manure, crop requirements, commercial fertilizer prices and application costs ( Koehler and Lazarus, 2007) T he two most important factors th at determine the net value of manure are its nutrient content and the distance it needs to be hauled before it is used, with greater nutrient content enhancing manure value and longer transportation distance reducing it (Ribaudo and Agapoff, 2005). Given the number of factors that affect the calculation of manureuse costs, best estimates are obtained utilizing producer specific values, that can capture

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32 the differences in manure production and nutrient content, land available, and crop demands, as well as manure handl ing equipment available, among others ( Koehler and Lazarus, 2007) Least Cost Ration Linear Programming Models for Dairy Cattle Linear programming is a quantitative method that deals with the analysis of optimization problems where the relationships between production factors are lineal (McCarl and Spreen, 1996; Simpson, 1989). Since its development in 1958, its use in agricultural economics has been widespread (Simpson, 1989; Pesti and Seila, 1999), serving as a complement to budgeting and as an analytical tool to analyze the feasibility of livestock enterprises (Simpson et al., 1989 ). In general, linear programming is considered an optimization procedure where a given response variable (e.g., ration cost) is maximized or minimized under a set o f constraints or restrictions (e.g., amount of DM intake, CP, energy required in ration). Use of this approach in determining least cost rations has been widespread in dairy production systems throughout the USA (Eastridge, 2006). One of the most important challenges in feeding dairy cows is finding the optimum balance between starch and fiber to meet their nutritional requirements and maintain rumen health. With the shift towards the use of total mixed rations (TMR) in the past 25 yr, producers increasingly have opted to use computerized systems to control diet composition and cost (VandeHaar and St. Pierre, 2006), many of which are least cost and ration evaluation programs such as the Spartan ration evaluator/balancer from Michigan State University, Corn ell Universitys CPM Dairy Program, or the PCDairy2 software from the University of California, Davis.

PAGE 33

33 Initial studies have found that this type of software constitutes a user friendly and accurate means of formulating rations for lactating dairy cows (Ho ward et al, 1968; Chandler and Walker, 1972; Black and Hlubik, 1980). An additional benefit is that these tools are adaptable to multiple research and producer management questions, such as the feasibility of incorporation of certain concentrates or forages in the ration. Recent studies also have used this application for the evaluation of dairy farm management activities, such as manure disposal costs (Hadrich et al., 2008), adjustment of CP levels in dairy heifer rations (Tozer, 2000), or dairy grazing m anagement (Duru et al., 2007). In the following chapters harvest management strategies for Tifton 85 bermudagrass will be evaluated. T he effects of stubble height and harvest interval will be examined in detail Responses measured and reported include DM production and nutrient removal (Chapter 3) and herbage nutritive value (Chapter 4) In addition, an assessment of the impact on ration cost of incorporating Tifton 85 bermudagrass greenchop as a forage source for lactating dairy cows is presented (Chapter 5) .

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34 CHAPTER 3 HARVEST MANAGEMENT EFFECTS ON FORAGE DRY MATTER PRODUCTION AND NUTRIENT REMOVAL OF TIFTON 85 BERMUDA GRASS Introduction Tifton 85 bermudagrass ( Cynodon spp .) is a n important warm season forage grass for use in the southeastern USA. The greater yields and quality of this grass compared to other Cynodon hybrids make it an ideal forage for livestock farming in the region, particularly for dairy and beef production (West et al., 1998; Hill et al., 2001). Tifton 85 has consistently produced dry matter (DM) yields that have been in the upper tier when evaluated against a number of other grasses under diverse management and environmental conditions (Sistani et al., 2004; Woodard et al., 2007; Marsalis et al., 2007). Also, the above average nutritive value makes it an increasingly accepted subtropical forage option for dairies in the southern USA (Hill et al., 2001). While it has shown greater DM yields than other bermudagrass hybrids such as Coastal (Mandebvu et al., 1999; Marsalis et al., 2007), Tifton 78 (Hill et al., 1993), and Tifton 44 (Hill et al., 2001), as well as seeded bermudagrass varieties including Wrangler, Cheyenne, Sahara, and Giant (Marsalis et al., 2007), the effects of mechanical defoliation on DM yields under sandy soil conditions in Florida have not been documented widely. Harvest interval and stubble height affect DM production and stand persistence (Mislevy and Everett, 1981). In general, infrequent cuttings of hybrid bermudagrasses have been shown to maximize DM yield (Holt and Lancaster, 1968; Hol t and Conrad, 1986; Mandebvu et al., 1999) and lower leaf to stem ratios (Prine and Burton, 1956). The literature indicates that low stubble heights are associated with maximization of

PAGE 35

35 yield ( Ethredge et al., 1973), but it also shows how lower stubbles can affect negatively the persistence of some species (Mislevy and Everett, 1981). The morphological characteristics of Tifton 85, particularly a more upr ight growth habit than Coastal bermudagrass (Burton et al., 1993), may require a different defoliation management approach than the close defoliation widely established for Coastal bermudagrass and other warm season perennial grasses (Holt and Lancaster, 1 968). Additionally, DM yields of warm season perennial grasses and particularly Cynodon species have shown a high potential for removal of N and P ( Newman et al., 2009). Newton et al. (2003) and Woodard et al. (2003) found that Tifton 85 removed 86 and 73% of N applied, respectively. Woodard et al. (2007) concluded that Tifton 85 would be the best warm season option for P removal from dairy effluent sprayfields in Florida after analyzing the P extraction potential of forage systems that included c orn plants ( Zea mays L.), perennial peanut ( Arachis glabrata Benth.), and forage sorghum [ Sorghum bicolor (L.) Moench.] as warm season components. Thus, understanding the effects of harvest interval and stubble height on DM yields is needed to determine the potential for excess soil nutrient removal by Tifton 85, and for establishing management guidelines for long term persistence. Based on the literature, the hypothesis of the study is that longer harvests and shorter stubble heights of Tifton 85 bermudagrass should produce greater DM yields. Specific objectives of this study were to i) quantify the DM production of Tifton 85 bermudagrass in response to harvest intervals and stubble heights and ii) determine the

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36 N and P removal under different harvest interval by stubble height treatment combinations. Materials and Methods Study s ite d escription This study was conducted during 2007 and 2008 on established hayfields of Tifton 85 bermudagrass in North C entral Florida. In 2007, t he study w as located on a commercial dairy farm near Bell in Gilchrist County, within the Suwannee River basin (2943'N and 8251'W). The s oils are excessively drained Kershaw fine sands (thermic, uncoated Typic Quartzipsamment) characterized by a very rapid permeability, slow surface runof f, water table below a depth of 10 m, and gently rolling topography (Soil Service Staff, 200 6 ). Soil pH was 7.4 Mehlich I extractable P, K, Ca, and Mg at the site were classified as either high or very high (Table 31), with values of 597 175 1993 and 220 mg kg1, respectively. Organic matter was 22.5 g kg1. During the period of the study (May to October), the experimental area received applications of solid manure and manure water at rates of 47.2 Mg DM ha1 and 1.7 ML ha1, respectively. These applications totaled to 144 kg ha1 of P and 148 kg ha1In 2008, t he study w as conducted approximately 16 miles south of the first location, also within the Suwannee River basin in N orth C entral Florida (2930'37.38"N, 8248'49.04"W). The soils were also moderately to excessively well drained Otella Candler fine sands ( l oamy, siliceous, semiactive, thermic Grossarenic Paleudalfs) characterized by a rapid permeability, slow surface runoff water table below a depth of 1.4 m, and gently rolling topography (Soil Service Staff, 200 6 ). Soil pH was 6.0 Mehlich I extractable P, K, Ca, and Mg at the site were 83 44 424, and 66 mg kg of N. 1, respectively. Organic m atter was 1 5.4 g kg1. Whereas no fertilizer was applied during

PAGE 37

37 the experiment, the field served as a feed lot for feeder calves during the fall and spring prior to initiation of this experiment. Table 31. Current interpretation for Mehlich 1 soil test results for agronomic and vegetable crops. Very Low Low Medium High Very High -----------------------------ppm -----------------------------P <10 10 15 16 30 31 60 >60 K <20 20 35 36 60 61 125 >125 Mg -<15 15 30 >30 Harvest m anagement and s ampling At both locations, the experimental area was a 3530 m (1050 m2) section of an established Tifton 85 bermudagrass hay field. The staging cut to initiate the experiment occurred on 26 June in both years Experimental units were 62.5 m (14.9 m2), with 2.5 m borders on each side. S ampling units consisted of a 61.25m (7.6 m2) strip from the center of the plot. Plots were harvested according to treatment (Table 32 ) during afternoon hours using a flail type mower. Stubble heights were achieved by adjusting the harvester to the desired height for each experimental unit. Fresh weight was measured, and subsamples of approximately 400to 500g were taken from the harvested material for dry weight determination by oven drying for 48 h at 55C. Samples were ground to pass a 1mm screen in a Wiley mill, and tissue N and P concentrations w ere determined by semiautomated colorimetry (Hambleton, 1977). Nitrogen and P removal (kg ha1) was calculated as the product of DM yield (kg ha1) by herbage tissue concentration ( g kg1 herbage). Additionally a weed assessment was conducted, where summer weeds present in the plots at the time of harvest were removed manually, counted and classified as either grass, broadleaf or Amaranthus sp

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38 Table 3 2 Harvest schedule for Tifton 85 harvest intervals in 2007 and 2008. 21 d 24 d 27 d 35 d Harvest Number 2007 2008 2007 2008 2007 2008 2007 2008 1 17 July (198) 17 July (199) 20 July (201) 21 July (203) 23 July (204) 23 July (205) 31 July (212) 31 July (213) 2 7 Aug. (219 ) 7 Aug. (220 ) 13 Aug. (225) 13 Au g. (226) 20 Aug. (232) 19 Aug. (232) 4 Sept (247) 4 Sept. (248) 3 28 Aug. (240) 28 Aug. (241) 6 Sept. (249) 5 Sept (249) 17 Sept. (260) 15 Sept (259) 9 Oct. (282) 9 Oct. (283) 4 17 Sept. (260) 18 Sept. (262) 1 Oct (274) 30 Sept. (274) 15 Oct. (288) 13 Oct. (287) 5 9 Oct. (282) 9 Oct. (283) 24 Oct. (297) 6 30 Oct. (303) Staging cut was on 26 June in both years. Day of year. Experimental d esign The experiment was analyzed as a randomized complete block design with a split plot arrangement of treatments with three replicates. Stubble heights were 8 and 16 cm and were assigned to main plots. Harvest interval levels were 21, 24, 27, and 35 d and were assigned to subplots, generating a total of eight treatments of stubble height by harvest interval level and a total of 24 experimental units (Figure 3 1). Stubble heights were selected with the goal of simulati ng those used by produce rs (8 cm), and a taller one (16 cm), that may be more appropriate for the growth habit of this grass. The 21, 24, and 27d harvest interval levels were selected to evaluate the effect on D M yield of harvesting before 28d of regro wth, which is likely the interval to be used for greenchop on dairies. The 35d level was selected to represent the longest interval within the recommended range for bermudagrass in Florida (Staples, 2003).

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39 2.5 m 2.5 m 6 m 2.5 m Tall stubble (16 cm) Short stubble (8 cm) Rep I 21 days 27 days 35 days 24 days Rep II Rep III Rep I Rep II Rep III Harvest frequency Figure 31. Experimental layout of defoliation management trial during 2007 and 2008.

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40 Data analysis Data were analyzed using PROC MIXED procedures of SAS (SAS Institute Inc., 2004) In all models, year, stubble height and harvest interval were considered fixed effects ; replicates and their interactions were modeled as random effects Total DM yields were calculated as the sum of DM from each harvest during the growing season. In order to study the seasonal trends in DM yields within each harvest interval, data was analyzed using the repeated measures statement in PROC GLIMMIX. The nature of the harvest interval effect was assessed using orthogonal polynomial contrasts. Because of the unequally spaced harvest interval levels, coefficients wer e obtained using the ORPOLY macro procedure in SAS (SAS Institute, 2004). Mean separation was further accomplished using least square means and the PDIFF option in SAS. All test differences were considered significant at P 0.05, while values at P were further discussed as trends. Results and Discussion Weather c onditions During both years of the study unusually dry conditions were present (Figure 32). In 2007, total rainfall was consi derably lower than the 59yr average (835 vs. 1331 mm, respecti vely), and reached 790 mm for the May through October period. The distribution reflected markedly drier January through Ma y and August periods that received less than 50% of the expected rainfall. In 2008, total rainfall was also considerably lower than the long term (51 yr) average (1031 vs. 1525 mm, respectively), and was only 571 mm for the May through October growing season. The distribution throughout the year also showed considerably drier April through July and September through December periods. The months of April, June and July received less than 55% of the expected rain, while the

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41 A B Figure 32. Monthly r ainfall for the study site in 2007 near Bell, Florida and the 59yr average (A) (SERC C 2008); and for the study site in 2008 near Chiefl and, FL and the 51yr average (B) (SERC C 2009). Bar indicates data collection period. month of May received only 7% of the typical rainfall. Additionally, whereas the month of August received greater than average rain, 45% occurred in a three day span (2427 August). Implications of these rainfall patterns will be discussed for the response variables below.

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42 Total DM y ields Although no year x HARVEST x STUBBLE interaction was detected ( P = 0.42), a significant ( P HARVEST interaction and a year STUBBLE interaction trend ( P = 0.10) were observed for total DM yield (Table 33). Because there were interactions with year, data were further analyzed by year. In both instances, main effects for HARVEST and STUBBLE were found (Table 33). Table 33 Observed significance level ( P value) from mixed models for the effects of harvest interval ( HARVEST ), stubble height ( STUBBLE) and year on total DM yields (Mg DM ha1 ). Year Source of variation 2007 2008 2007 2008 HARVEST < 0 .0001 < 0 .0001 0.0008 STUBBLE 0.0005 0.0474 0.0084 HARVEST *STUBBLE 0.6521 0.3907 0.7080 Year < 0 .0001 Year* HARVEST < 0 .0001 Year*STUBBLE 0.0945 Year* HARVEST*STUBBLE 0.42 00 In 2007, harvest interval had a significant effect on total DM yield ( P linearly from 7.3 Mg ha1 under 21and 24d harvests to 10.8 Mg ha1 for the 35 d interval (Table 34). Stubble height also had a significant effect on DM yield during this year ( P = 0.05), with the 8cm height producing ~9% more DM ha1 than the 16 cm stubble, at 8.8 and 8.1 Mg DM ha1, respectively. In 2008, harvest interval had a significant effect on total DM yield ( P 1 for 21to 27 d harvests, while 35d harvests presented the lowest values at 5.6 Mg ha1. As in 2007, stubble height had a strong effect on DM yield ( P = 0.01); with the short stubble height producing 27% greater yield than the tall stubble, at 7.3 and 5.8 Mg ha1, respect ively.

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43 Table 34 Comparison of DM yield means as affected by harvest interval ( HARVEST ) and stubble height ( STUBBLE) in 2007 and 2008. Means within a treatment variable and year are different if not followed by the same letter, P PC, Polynomial contrast for the effect of harvest interval (L = linear, Q = quadratic, C = cubic); Indicates significant differences at P Indicates significant differences at P Dry matter yield in 2007 showed the general trends reported by Ethredge et al. (1973), Pedreira et al. (1999) and Mandebvu et al. (1999) for hybrid bermudagrasses, where longer periods between defoliation e vent s maximize d DM yield The causes of the unexpectedly low yield observed in 2008 at 35d intervals are unclear and rather seem to contradict most tropical forage research. The low levels of residual N associated with the lack of fertilization were likel y involved in the lower DM yields observed for all harvest intervals in 2008. The greater yields obtained in both years with intervals up to 27 d could generally be associated with the greater light interception by the stand during the growing season (Morgan and Brown, 1983; Pedreira et al., 2000), which would allow more DM accumulation despite fewer harvests. Additionally, the typically greater DM concentration of older herbage compared to younger material could have contributed to the yield increase (Danley and Vetter, 1973). The differences in yields between stubble heights Year Number of Harvests HARVEST (d) 2007 2008 2007 2008 ----Mg ha 1 ----21 7.3 c 6.4 b 6 5 24 7.3 c 6.6 b 5 4 27 8.4 b 7.4 a 4 4 35 10.8 a 5.6 c 3 3 SE 0.39 0.24 PC L** L**, Q**, C* STUBBLE (cm) 8 8.8 a 7.3 a 16 8.1 b 5.8 b SE 0.19 0.31

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44 also follow the trends described in studies across different hybrid bermudagrass es, which suggest that leaving shorter residual stubble heights after defoliation r esults in greater yields throughout the year (Holt and Lancaster, 1968; Ethredge et al., 1973). Seasonal (by harvest) DM yields Analysis of the data by harvest by year shows that there were differences in DM yield between harvest events for all harvest in terval treatments in the study (Table 35 ; Fig. 3 3 and 34). For each harvest interval in 2007, yields were greater initially and lower at the last harvest event each year. In this year there was also a significant harvest event STUBBLE interaction for all harvest interval treatment s except 27 d [21 d ( P d ( P P those from short stubble (Table 36 ). Furthermore, if we take into consideration that total yields u nder short stubble were only ~9 % greater than those under tall stubble (Table 33 ), producers could benefit from obtaining more stable yields throughout the season leaving taller stubble heights. In 2008, significant harvest event by stubble height inte ractions were observed only for 27and 35 d harvests ( P 0.01) (Table 37). While the reasons for the trends observed for 27d are not clear, the proportionally greater decrease of 8cm stubble yields in the last harvest of the 35d treatment appeared to have produced the interaction. Table 35 Observed significance level ( P value) from mixed models of the effects of stubble height ( STUBBLE ) and harvest event (HE) on total DM yield analyzed by harvest interval (HARVEST) in 2007 and 2008. Harvest interval (d) -----21 ----------24 ----------27 ----------35 -----Source of variation 2007 2008 2007 2008 2007 2008 2007 2008 STUBBLE 0.9591 0.0571 0.2075 0.1068 0.0426 0.018 0 0.3545 < 0 .0001 H E < 0 .0001 < 0 .0001 < 0 .0001 0.0004 < 0 .0001 < 0 .0001 < 0 .0001 < 0 .0001 STUBBLE x H E < 0 .0001 0.2713 0.0029 0.4035 0.3764 < 0 .0001 0.0286 0.0012

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45 0 1 2 3 4 5 6 1 2 3 4 5 6DM yield (Mg ha1)21 d Short Tall 0 1 2 3 4 5 6 1 2 3 4 5 24 d Short Tall 0 1 2 3 4 5 6 1 2 3 4DM yield (Mg ha1)Harvest27 d a b c c 0 1 2 3 4 5 6 1 2 3 Harvest35 d Short Tall Figure 33. Dry matter yield response of Tifton 85 bermudagrass to harvest event by harvest interval (HARVEST) in 2007. represents LSM significant differences ( P height harvest interaction was detected ( P letters are different ( P parenthesi s. Standard errors (SE) were 0. 1 1 (21 d), 0.13 (24 d), 0.15 (27 d), and 0.28 (35 d) (198) (219) (240) (260) (282) (303) (212) (247) (282) (201) (225) (249) (274) (297) (204) (232) (260) (288) 8 cm 16 cm 8 cm 16 cm 8 cm 16 cm

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46 0 1 2 3 4 1 2 3 4 5DM yield (Mg ha1)21 d a b c d a 0 1 2 3 4 27 54 81 108 DM yield (Mg ha1)Harvest27 d Short Tall 1 2 3 4 0 1 2 3 4 1 2 3 424 d a b c d 0 1 2 3 4 35 70 105 Harvest35 d Short Tall 1 2 3 Figure 34. Dry matter yield response of Tifton 85 bermudagrass to harvest event by harvest interval (HARVEST) interaction in 2008. represents LSM significant differences ( P harvest when stubble height harvest interaction was detected ( P harvests with different letters are different ( P parenthesis. Standard errors (SE) were 0.18 (21 d), 0. 32 (24 d), 0.1 4 (27 d), and 0. 09 (35 d) (199 ) (220 ) (24 1 ) (262 ) (2 83 ) (203 ) (226 ) (24 9 ) (274) (205 ) (232 ) (2 59 ) (287) (213 ) (248 ) (2 83 ) 8 cm 16 cm 8 cm 16 cm

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47 Table 3 6 Stubble height ( STUBBLE) harvest event effects on DM yield analyzed by harvest interval (HARVEST) in 2007. Harvest event HARVEST (d) STUBBLE (cm) 1 2 3 4 5 6 SE ------------------------Mg ha 1 ----------------------21 8 2.10 a 0.56 b 2.57 a 0.68 a 1.13 a 0.34 a 0.90 16 1.87 a 1.79 a 1.65 b 0.88 a 0.93 a 0.22 a 0.65 24 8 3.25 a 1.20 a 1.91 a 0.81 b 0.52 a 1.09 16 2.72 b 1.21 a 1.32 b 1.35 a 0.33 a 0.85 27 8 3.58 A 2.94 B 1.14 C 1.54 C 1.15 16 2.91 2.59 1.04 1.16 0.96 35 8 5.16 a 4.78 a 1.12 a 2.23 16 3.78 b 5.19 a 1.49 a 1.87 Stubble height means within each harvest interval and harvest event not followed by the same lower case letter are different at P Harvest event means across stubble heights within a row not followed by the same upper case letter are different at P Table 37 Stubble height ( STUBBLE) harvest event effects on DM yield, analyzed by harvest interval (HARVEST) in 2008. Harvest event means across stubble heights within a row not followed by the same upper case letter are different at P Stubble height means within each harvest interval and harvest event not followed by the same lower case letter are different at P Harvest event HARVEST (d) STUBBLE (cm) 1 2 3 4 5 SE ------------------------Mg ha 1 ------------------21 8 1.28 C 1.29 B 2.47 A 2.04 A 0.17 C 0.9 16 0.57 1.06 1.87 2.02 0.03 0.8 24 8 2.32 B 1.34 C 2.92 A 0.56 D 1.0 16 1.57 1.77 2.34 0.34 0.8 27 8 2.65 a 2.26 b 2.73 a 0.62 1.0 16 1.26 b 3.61 a 1.21 b 0.51 1.4 35 8 2.96 a 3.05 a 0.50 1.4 16 2.06 b 2.04 b 0.68 0.8

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48 It would also seem that under these conditions, 35d harvests do not take full advantage of the forages regrowth ca pacity, suggesting that more frequent harvests would produce more DM on a yearly basis. Nonetheless, this would seem to contradict most research dealing with defoliation management of hybrid bermudagrasses and the results obtained in 2007. The low yield observed for 21and 24d intervals in the first two harvests compared to the following two harvests were likely due to the unusually dry conditions present at the start of the growing season; where the months of June and July received less than 55% of the average rainfall. In general, the harvest event trends observed are to be expected, since environmental conditions, such as water and temperature, or daylength, and plant phenological stages vary throughout the year. In both years, harvests occurring duri ng times of adequate moisture from midJune to August tended to have greater yields than those performed later in the year when the days were shorter (Sinclair et al., 2001; Newman et al., 2007). Periods of lower rainfall and temperature that occur in Nort h C entral Florida are can reduce DM yields, while a stronger partitioning of photosynthate to storage organs during the fall period can also reduce herbage DM accumulation (Sinclair et al., 2003). Tifton 85 bermudagrass nutrient r emoval Averaged across years, main effects for STUBBLE were detected for N and P removal ( P 0.016 and P 0.02, respectively; Table 38 ). For both nutrients, stubble heights resulting in the greatest yields also resulted in the highest removal (Table 39 ), with the 8cm stubbl e management removing 29.5 and 3.5 kg ha1 more N and P, respectively, than the 16cm stubble management

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49 Table 38 Observed significance level ( P value) from mixed models of the effects of harvest interval ( HARVEST ) and stubble height ( STUBBLE) on total N and P removal, analyzed by year. N P Effect 2007 2008 2007 2008 2007 2008 2007 2008 HARVEST 0.0002 < 0. 001 < 0. 001 0.0001 < 0.0 01 0 < 0.0 01 0 STUBBLE 0.0016 0.0768 0.0055 0.0175 0.2008 0.0092 HARVEST*STUBBLE 0.7894 0.507 0 0.2494 0.6616 0.5322 0.3594 Year < 0. 001 0 0.0004 Year* HARVEST < 0. 001 0 <0. 001 0 Year*STUBBLE 0.1545 0.2039 Year* HARVEST *STUBBLE 0.2686 0.2601 Table 39. Yield, nutrient concentration, and nutrient removal of Tifton 85 bermudagrass in response to increasing harvest interval ( H ARVEST ) and two stubble heights ( STUBBLE) in 2007 and 2008. Harvest (d) 2007 2008 2007 2008 2007 2008 2007 2008 2007 2008 DM yield N P N removal P removal --kg ha -1 ---% --------% ----kg ha -1 --kg ha --1 --21 7300 c 6400 b 3.2 a 2.6 a 0.31 a 0.30 a 231 c 167 a 23 b 19 b 24 7300 c 6600 b 3.1 a 2.4 b 0.30 ab 0.29 b 222 c 156 b 22 b 19 b 27 8400 b 7400 a 3.1 a 2.3 bc 0.29 b 0.30 a 262 b 170 a 24 b 22 a 35 10800 a 5700 c 2.9 b 2.2 b 0.29 b 0.27 c 310 a 125 c 31 a 15 c STUBBLE (cm) 8 8800 a 7300 a 3.0 2.4 0.29 0.29 221.5 a 23.5 a 16 8100 b 5800 b 3.0 2.3 0.29 0.28 192.0 b 20.0 b Columns with different lower case letters are different at P A year HARVEST interval interaction was detected for both N and P removal ( P 0.01 ; Table 38 ) ; consequently the data were analyzed by year. In both years of the study, main effects for harvest interval we re significant ( P 0.01) for N and P removal In 2007, 21 d harvests removed 231 and 23 kg1 ha1 yr1 of N and P, respectively, while 35d harvests removed 310 and 31 kg1 ha1 yr1 (Table 39 ). Thus, harvest at 35d removed 35% more N and P than harvesting at 21 d intervals.

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50 Overall, these findings coincide with previous research involving Tifton 85. Woodard et al. (2003) studied forage systems on dairy sprayfields in North Florida and found that Tifton 85 as a component of a corn bermudagrass rye forage system removed on average 191 kg ha1 of N in two cuttings at a 3cm stubble. In a similar study, Woodard et al. (2007) reported that Tifton 85 harvested four to five times as a part of a bermudagrass rye forage system removed 33 kg ha1 of P from dairy manure sprayfields receiving an average of 120 kg P ha1 yr1. These authors also reported that Tifton 85 re moved only an average of 8 kg P ha1 when a component of a cornbermudagrass rye system that was harvested twice during the warm season under the same effluent rate. Brink et al. (2004) reported annual removal rates of 220 and 33 kg ha1 yr1of N and P, respectively, for Tifton 85 receiving swine effluent at average rates of 39 and 202 kg ha1 yr1An important consideration when studying the phytoremediation potential of forage grasses is the proportion of nutrients applied that were removed in the herbage. When the amounts of solid manure and manure irrigation water applied during the 2007 growing season are taken into consideration, 35d harvests extracted 22% of P and approximately 2.1 times as much N as was applied. Although the nutrient application data does not take into consideration the amounts already available in the soil from previous appl ications, the results highlight the potentially benefits of using Tifton 85 bermudagrass for excess nutrient extraction. of P and N, respectively. A common conclusion from these studies is that forages with greater DM yields typically removed the most nutrients from sprayfields.

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51 Weed a ssessment Summer weed count data taken on each plot during the 2008 season proved insufficient for further statistical analysis, since very little weed presence was detected. The few observations recorded did not follow any discernible harvest interval or stubble height pattern. Nevertheless, a plot weed coverage estimation conducted in winter (5 Mar. 2009) revealed that experiment al units under the short stubble height had on average 48 16% weed cover, compared to plots with a taller stubble which had 17 6.9% weed cover. Main species present included cudweed ( Gnaphalium sp. ), golden rod ( Solidago sp. ) and an unidentified broadle af in the Brassica genus. Summary and Conclusions These results suggests that the lower residual leaf coverage in plots of shorter stubble height likely allowed more light penetration, increasing the number of weeds germinating from seed. This highlights another potential benefit of harvesting Tifton 85 at higher stubbl e since less weed coverage could lead to fewer herbicide applications, as well as overall greater yields and nutritive value. Tifton 85 bermudagrass is considered a high quality warm season grass for livestock production in the S outheast USA It has been known to produce greater DM yield than other widely grown hybrid bermudagrasses under various environmental and management conditions. Results from the defoliation management trial that test ed the effects of harvest interval (21, 24, 27, and 35 d) and stubble height (8 and 16 cm ) on herbage DM yield lead to the following conclusions: Under 2007 conditions, total yields were consistently greater as the interval increased from 21 and 24 d to 35 d, suggesting that longer periods between harvests maximize total DM yields. In 2008, overall yi elds were probably affected by water stress

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52 and lack of N fertilization, and presented unusually low yields for the 35d harvest interval. Across years, the short stubble height produced more DM than the tall level, although this difference was considerably more pronounced under the water and N restricted conditions in 2008. In terms of seasonality of DM production, in both years greater yields were typically p resent when environmental conditions were most conducive to vegetative growth, particularly in terms of water availability. In 2007, harvest event stubble height interactions were present for all but the 27d level, and while significant differences were found between stubble heights for a given harvest, these were usually not of great magnitude. In addition, tall stubble management tended to result in more consistent yields throughout the season, possibly suggesting a management that may be more benefici al for producers, because of the dependability of yields. In addition, the lower stubble management could hinder persistence through multiple growing seasons due to the high incidence of weeds observed during winter. In 2008, interactions between harvest i nterval and stubble height were observed only for 27and 35d harvests. While the causes of the unusual fluctuations in yields during the initial harvests under 27 d are not clear, they are likely due to the differential effects of water stress and low so il N levels on the treatments. Patterns of removal N and P followed that of DM yield patterns in both years. While no significant harvest interval stubble height interactions were detected, harvest interval by year interactions were detected f or N and P removal. The 35and 27d harvests removed the most N and P in 2007 and 2008, respectively. Stubble height m ain effects were found for both N and P removal, with the short stubble removing 29.5

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53 and 3.5 kg ha1Overall, the results suggest that both harvest interval and stubble affect DM yields and soil nutrient removal of Tifton 85 bermudagrass. While longer intervals and shorter stubble heights seem to increase DM production and excess soil nutrient removal, using taller stubble heights in North Central Florida conditions may be necessary in order to guarantee stand persistence. more N and P, respectively, than the taller stubble. In addition, 35d harvests in 2007 removed 22% of applied P and 2.1 times as much N as was applied in either manure or manure irrigation water, suggesting that Tifton 85 can be a an important tool for phytoremediation in dairy sprayfields.

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54 CHAPTER 4 HARVEST MANAGEMENT EFFECTS OF TIFTON 85 BERMUDAGRASS ON HERBAGE NUTRITIVE VALUE Introduction One of the main goals i n forage production for livestock is to maximize nutritive value. Nutritive value of forages is strongly affected by maturity, season, and management (Moore, 1994). Forage nutritive value declines with time because of the lower leaf to stem ratio and lower protein and energy associated with fiber deposition in mature forage (Jung and Allen, 1995).The challenge remains to maintain high forage nutritive value that meets the nutritional requirements of livestock without compromising yield or stand persistence (Holt and Conrad, 1986). Harvest interval is cr itical in determining herbage nutritive value of bermudagrasses (Mislevy and Everett, 1981), and, i n general, longer harvest intervals of warm season grasses tend to decrease leaf to stem ratios and herbage nutritive value (Monson and Burton, 1982), while stubble height effects tend to be less critical. Research on Tifton 85 bermudagrass management has shown that nutritive value varies with harvest interval and season. Fiber fractions have been found to increas e with age at harvest, causing a reduction in herbage crude protein concentrat ion and digestibility (Mandebvu et al., 1999). Several studies in Florida ( Mislevy and Martin, 2006; Johnson et al., 2001) have found strong seasonality effects on herbage crude protein concentrations, with greater values in these studies occurring early and late in the growing season. In terms of the effects of stubble height on nutritive value of Tifton 85 there is a limited amount of research currently available. While the potential benefits of using Tifton 85 in dairy production have been studied they have been limited to long harvest

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55 intervals ( Ruiz et al., 1995). Further research on Tifton 85 is needed that evaluates stubble height under a range of shorter harvest intervals in order to determine the effects on herbage nutritive value. The objective of this study was to quantify the effects of harvest interval and stubble height on Tifton 85 herbage crude protein (CP), P, in vitro digestible organic matter (IVDOM) and neutral detergent fiber (NDF) Materials and M ethods Study s ite d escription This study was conducted during 2007 and 2008 on established hayfields of Tifton 85 bermudagrass in N orth C entral Florida. In 2007, the study was located in a commercial dair y farm near Bell, Gilchrist County, within the Suwannee River basin (2943'N and 8251'W). In 2008, t he study w as conducted approximately 16 miles south of the first location, also within the Suwannee River basin in North C entral Florida (2930'37.38"N, 8248'49.04"W). Soils at these locations, t he soil chemical analysis and weather description s were detailed in Chapter 3 The e xperimental area was a 35 30m (1050 m2) section of an established Tifton 85 bermudagrass hay field at each site. Experimental units were 14.9 m2 Treatments (6.1 2.5 m), with 2.5 m borders on each side. Treatments were arranged as a split plot experiment in a randomized complete block design with three replicates. Stubble height levels were 8 and 16 cm and were assigned to main plots, while harvest interval levels were 21, 24, 27, and 35 d and were assigned to sub plots, resulting in a total of eight stubble height by harvest interval combinations and a total of 24 experimental units (Figure 2 1). Stubble heights were selected wi th the goal of representing those used by producers (8 cm), and a taller one (16 cm), that may be more appropriate considering the growth habit of Tifton 85. The

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56 2 1 24 and 27d harvest interval levels were selected in order to evaluate the effects on n utritive value of harvesting before 28 d of regrowth, which is the likely range of intervals to be used for greenchop on dairies, while the 35d level was selected to represent the longest interval within the recommended range for bermudagrass in Florida ( Staples, 2003). Herbage sampling and processing Sampling units consisted of a 6.1 1.25 m (7.6 m2Laboratory a nalysis ) strip, harvested with a flail type mower for DM yield calculation. A 400500 g subsample was taken from the fresh harvested material for nutritive value analysis. Samples were dried for 48 to 72 h at 55C in a forced air dryer to constant dry weight. Subsequently, samples were ground using a Willey mill to pass a 1mm screen. Herbage samples were analyzed for CP, P, IVDOM, and N DF. Samples f or N and P analysis were digested using a modification of the aluminum block digestion proc edure of Gallaher et al. (1975) Nitrogen and P in the digestate w ere determined by semiautomated colorimetry (Hambleton, 1977). Crude protein was calculated as N multiplied by 6.25. A modification of the two stage procedure of Moore and Mott (1974) was used to determine IV DOM Neutral detergent fiber was analyzed using the method described by Van Soest et al. (19 91) utilizing the ANKOM filter bag technique (ANKOM Technology, Macedon, NY, USA) Statistical a nalysis Data were analyzed using PROC MIXED procedures of SAS (SAS Institute Inc., 2004) In all models, year, stubble height and harvest interval were considered fixed effects and blocks considered random Total (yearly) nutritive value data were

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57 calculated as means weighted by DM yields. In order to study the seas onal trends in nutritive value within each harvest interval; data was analyzed using the repeated measures statement in PROC GLIMMIX. The nature of the harvest interval effect was assessed using orthogonal polynomial contrasts. Because of the unequally spaced harvest interval levels, coefficients were obtained using the ORPOLY macro procedure in SAS (SAS Institute, 2004). Mean separation was done using the LS MEAN statement of PROC MIXED, and the PDIFF option ( SAS Institute Inc., 2004). Res ponses were analyzed by year and by harvest in order to quantify the effect of harvest event in nutritive value as affected by the treatments All test differences were considered significant at P 0.05 while values at P Results and Discussion Crude protein There were only main effects ( P interval and year on herbage CP concentration (Table 41), however, a trend toward a harvest interval year interaction was found (P = 0. 0 8 ), and results are further described by year. During the 2007 season no differences were found across stubble heights, and c rude protein values averaged 191 g kg1. Similar result s were found by Pedreira et al. (1999) in a study using Florakirk bermudagrass in North Florida. For three postgraze stubble heights (8, 16, and 24 cm), no stubble height effects were detected for herbage CP. Although the study was under grazing conditions, t he lack of differences between the stubble heights sugges ts that total CP concentrations are fairly similar when defoliatin g above an 8cm stubble height.

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58 Table 41. Observed significance level ( P value) from mixed models of the effects of stubble height ( STUBBLE ) and harvest interval (HARVEST ) on Tifton 85 herbage CP, P, IVDOM and NDF concentrations in 2007and 2008. Year Nutrient Source of variation 2007 2008 2007 2008 CP HARVEST <0.0 01 0.0007 0.0006 STUBBLE 0.6257 0.682 0 0.2475 HARVEST*STUBBLE 0.2556 0.1344 0.7373 Year < 0. 001 Year* HARVEST 0.0756 Year*STUBBLE 0.2495 Year* HARVEST*STUBBLE 0.7542 P HARVEST 0.0005 0.0459 0.0006 STUBBLE 0.9055 0.8805 0.2475 HARVEST *STUBBLE 0.1327 0.3803 0.7373 Year 0.2342 Year* HARVEST 0.0318 Year*STUBBLE 0.4374 Year* HARVEST*STUBBLE 0.4425 IVDOM HARVEST < 0. 001 < 0.00 1 0.0014 STUBBLE 0.2474 0.9581 0.1367 HARVEST*STUBBLE 0.0852 0.1163 0.2441 Year <0. 001 Year* HARVEST 0.2018 Year*STUBBLE 0.2161 Year* HARVEST*STUBBLE 0.3205 NDF HARVEST <0. 001 0.0003 0.0002 STUBBLE 0.2905 0.8781 0.184 0 HARVEST*STUBBLE 0.0266 0.0237 0.3332 Year <0. 001 Year* HARVEST 0.0992 Year*STUBBLE 0.2044 Year* HARVEST *STUBBLE 0.8959

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59 Crude protein, however, varied with harvest interval Shorter intervals ( 21to 27d harvest s) showed no differences in total CP concentration in 2007, averaging 194 g kg1; while at longer harvest intervals (35 d), a drop of 7% to 1 80 g kg1 was observed ( Table 4 2 ). D uring 2008, CP was 148 g kg1 averaged across stubble heights. A 15% decline in CP con centration after 21d was observed, falling from 163 to 137 g kg1When the analysis was performed by harvest within years (Figure 41), CP was at or above 1 7 0 g kg at 35 d ( Table 4 2 ). T he overall lower values observed when compared to 2007 are likely associated with the lack of N fertilization. 1 during the first 240 d in 2007 for each of the harvest intervals In 2008, t rends were similar to those in 2007, but CP was overall lower averaging 148 g kg1 across stubble heights and harvests Recent findings by Alderman (2008) studying the regrowth dynamics of T ifton 85 as affected by N fertilization shows differences that exceeded 100 g kg1 in CP concentration between treatments receiving no N fertilizer and those with 135 kg ha1Phosphor us of N per harvest. These findings are similar to those obtained by Vendramini et al. (2008) and Silveira et al. (2007). Also, a stubble height harvest interaction was detected for 27d harvests in 2008 (Figure 4 2). While the exact reason for this pattern is unclear, tall stubble (16 cm) harvests were noticeably more homogenous in CP concentration than short stubble (8 cm) harvests. Year by HARVEST eff ects were found for herbage P concentration ( P 3 ), but there were no year or stubble height main effects (Table 42). In 2007, highest values were obtained for 21and 24d harvests, averaging 3.0 g kg1, while lowest values were for 27and 35d harv ests, with 2.9 g kg1. The differences observed could be due to the dilution of P and other plant nutrients when more DM is accumulated with the onset of

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60 Table 4 2 Comparison of total (year) herbage crude protein (CP) and phosphorous (P ) means as affecte d by harvest interval ( HARVEST ) for 2007 and 2008. Year HARVEST (d) Stubble height (cm) 2007 2008 ---CP (g kg 1 DM) ---21 197 a 163 a 24 191 a 148 b 27 194 a 144 bc 35 180 b 137 c PC L** L**, Q* SE 2.8 3.2 8 190 150 16 192 146 SE 2.9 2.2 ----P (g kg 1 DM) ---21 3.1 a 3.0 a 24 3.0 ab 2.9 b 27 2.9 b 3.0 a 35 2.9 b 2.7 c PC L**, C** L**, Q**, C** SE 0.0 9 0.0 2 Means with a column not followed by the same lower case letter are different at P 0.05; PC= polynomial orthogonal contrast; L, Q and C represent linear, quadratic and cubic effects, respectively. and ** represent significant differences at the P 0.05 and P 0.01 levels, respectively. maturity. In 2008 the results show no clear trend in herbage P concentration, with 21and 27d harvests obtaining the highest values at 3.0 g kg1. In terms of harvest interval it should be noted that while statistical differences were found, the values obtained sugge st that in biological terms the differences are not important Herbage P concentrations found were similar or higher than those reported for other bermudagrasses ( McLaughlin et al., 2004) and Tifton 85 specifically (Woodard et al., 2007; Brink et al., 200 4 ) In both years, soils presented very high Mehlich I extractable P levels (Chapter 3) and consequently it can be considered that P deficiency was not present. Thus, the small differences found indicate that Tifton 85 tends to keep fairly stable herbage P c oncentration across defoliation regimes.

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61 100 120 140 160 180 200 220 240 1 2 3 4 CP (g kg1)Harvest27 d a b b ab 100 120 140 160 180 200 220 240 1 2 3 4 5 6 CP (g kg1)21 d a a a b b a 100 120 140 160 180 200 220 240 1 2 3 4 5 24 d 100 120 140 160 180 200 220 240 1 2 3 Harvest35 d a b b Figure 4 1. Crude protein (CP) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2007. Harvests with different low er case letters are different at P 0.05. Day of year is presented for each harvest in parenthes i s. Standard errors (SE) were 6.8 (21 d), 6.2 (24 d), 4.7 (27 d), and 4.4 (35 d) (198) (219) (240) (260) (282) (303) (201) (225) (249) (274) (297) (204) (232) (260) (288) (212) (247) (282)

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62 50 70 90 110 130 150 170 190 1 2 3 4 5CP (g kg1)21 d b ab a c d 50 70 90 110 130 150 170 190 1 2 3 424 d b a a c 50 70 90 110 130 150 170 190 1 2 3 4 CP (g kg1)Harvest27 d Short Tall 50 70 90 110 130 150 170 190 1 2 3 Harvest35 d Figure 42 Crude protein (CP) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2008. represents significant differences ( P harvest event interaction was detected ( P low er case letters are different at P Standard errors (SE) were 5 .1 (21 d), 6.4 (24 d), 5.8 (27 d), and 4.3 (35 d) (199 ) (220 ) (24 1 ) (262 ) (2 83 ) (203 ) (226 ) (24 9 ) (274) (205 ) (232 ) (2 59 ) (287) (213 ) (248 ) (2 83 ) 8 cm 16 cm

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63 In v itro d igestible o rganic m atter There were significant harvest interval main effects for IVDOM (P 0. 01) as well as year main effects (P 0.0 1) (Table 41). Since there were also trends indicating a stubble height harvest interval effect (P = 0.0 9 ), the interaction is further discussed. These trends show that there were only differences between stubble heights under 21d intervals, where the 8cm height produced 588 g kg1of IVDOM compared to 565 g kg1 under the 16cm stubble (Table 43). The reason for this difference is unclear. Polynomial contrasts indicate that IVDOM declined linearly with increasing harvest interval across stubble heights, from an average of 577 g kg1 at 21 d to 513 g kg1When the analyses were conducted by harvest in 2007 for 21d harvest interval IVDOM varied less for taller stubbles than short (Figure 43). For 21 d, tall stubble had significantly lower IVDOM ( average of 593 g kg at 35 d a reduction of approximately 11% (Table 43). These data support the literature indicating that forage digestibility declines with maturity. Reductions in leaf to stem ratio and the accumulation of secondary cell wall are associated with maturity in tropical grasses (Buxton and Redfearn, 1997) 1) during the first t wo harvests of the seaso n, while the short stubble height had the l owest value in the last harvest, at 355 g kg 1. On th e other hand, the trend for 24 d was reversed; tall stubble had the highest digestibility during the start of the season ( average of 671 g kg1) and the lowest (520 g kg1) at the end. It should be noted that the majority of the differences observed were in the 5 to 10% range, suggesting that Tifton 85 maintained a relatively consistent digestibility over time for this harvest interval The exception would be the final harvest of the 21 d interval where the tall stubble had 38% more digestibility than the shorter stubble. Both 27and 35d intervals showed no differences among harvests, suggesting

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64 Table 43. Comparison of total (year) in vitro digestible organic matter (IVDOM) means as affected by the stubble height harvest interval interaction. Stubble height (cm) HARVEST (d) 8 16 --IVDOM (g kg 1 DM) --21 588 a 565 b 24 558 a 571 a 27 549 a 549 a 35 520 a 505 a PC L* L* SE 7. 2 --NDF (g kg 1 DM) --21 670 b 686 a 24 685 a 680 a 27 696 a 698 a 35 702 a 702 a PC L** L** C SE 3. 3 Means within a row followed by different lower case letters are different at P 0.05 *, ** represent s significant differences at the P and P 0.01 level s, respectively PC= polynomial orthogonal contrast for harvest effect across stubble. L represents linear effects. that IVDOM for longer regrowth intervals varies little throughout the season. In 2008, when analyses were conducted by harvest (Figure 44), lowest IVDOM was observed in harvests at the beginning and the end of the growing season, except for 21 d harvests that had greater IVDOM in the first three harvests. Although the 35d harvest interval showed a stubble height harvest event interaction, the differences were in the 5 to 8% range, and also exhibited declining trends in IVDO M towards the end of the season. During this time, less favorable growing conditions, more dead material, and possibly lower leaf to stem ratios in plants could lower digestibility. These results also support those from several studies with bermudagrasses (Monson and Burton, 1982; Mislevy and Martin, 2006; Marsalis et al., 2007) and with Tifton 85 bermudagrass (Mandebvu et al., 1999; Johnson et al., 2001) in the Southeast USA.

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65 0 100 200 300 400 500 600 700 800 1 2 3 4 5 6 IVDOM (g kg1)21 d Short Tall 0 100 200 300 400 500 600 700 800 1 2 3 4IVDOM (g kg1)Harvest27 d 0 100 200 300 400 500 600 700 800 1 2 3 4 5 24 d Short Tall 0 100 200 300 400 500 600 700 800 1 2 3 Harvest35 d Figure 4 3 In vitro digestible organic matter (IVDOM) response of Tifton 85 bermudagrass to harvest event by harvest interval levels in 2007. represents significant differences (P 0.05) between stubble heights for a given harvest when stubble height har vest event interaction was detected (P 0.05). When no interaction was present, harvests with different low er case letters are different (P 0.05). Day of year is presented for each harvest in parenthesis. Standard errors (SE) were 16.8 (21 d), 20.1 (24 d), 36.1 (27 d), and 18.5 (35 d) (198) (219) (240) (260) (282) (303) (201) (225) (249) (274) (297) (204) (232) (260) (288) (212) (247) (282) 8 cm 16 cm 8 cm 16 cm

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66 0 100 200 300 400 500 600 700 1 2 3 4 5 IVDOM (g kg1)21 d a a a b b 0 100 200 300 400 500 600 700 1 2 3 4 24 d a b c c 0 100 200 300 400 500 600 700 1 2 3 4IVDOM (g kg1)Harvest27 d a b b c 0 100 200 300 400 500 600 700 1 2 3 Harvest35 d Short Tall Figure 44 In vitro digestible organic matter (IVDOM) response of Tifton 85 bermudagrass to harvest event by harvest interval level s in 2008. represents significant differences (P harvest when stubble height harvest event interaction was detected (P present, harvests with different lower case letters are different at P harvest in parenthesis Standard errors (SE) were 12.3 (21 d), 10.1 (24 d), 11.5 (27 d), and 9.2 (35 d) (199 ) (220 ) (24 1 ) (262 ) (2 83 ) (203 ) (226 ) (24 9 ) (274) (205 ) (232 ) (2 59 ) (287) (213 ) (248 ) (2 83 ) 8 cm 16 cm

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67 Neutral detergent fiber Fiber concentration measured by NDF presented stubble height harvest interval interaction effects ( P ). Neutral detergent fiber was 16 units greater for the 16 cm than the 8 cm stubble height at 21 d (Table 4 3). No differences were observed among stubble heights for all other harvest intervals in the study. P olynomial contrasts across stubble heights suggest that NDF concentration increases with increasing harvest interval and maturity. Harvests at 21 d had an average NDF concentration of 678 g kg1, while those done at 35 d intervals were 3.4% greater, averag ing 718 g kg1. Although the reasons for greater NDF concentrations under 16 cm vs. 8 cm stubble heights for 21d harvests are unclear, the greater NDF values observed under longer harvest intervals coincides with research in forage management. Overall, longer regrowth periods are associated with greater secondary plant cell wall deposition and reduced digestibility (Buxton and Redfearn, 1997). Additionally, with longer intervals between harvests we can typically expect leaf to stem ratios to lower, since m ore DM is accumulated in stems than in leaves with increasing maturity, raising the proportion of lignified tissue in herbage (Buxton and Redfearn, 1997). These results are also consistent with previous findings for Tifton 85 by Mandebvu et al. (1999), whi ch also found an increase in NDF concentration from 21to 35d harvests, while Johnson et al. (2001) reported values that were in the 745 to 788 g kg1 Summary and C onclusions range, and that only showed differences between 7and 35d harvest intervals. Results from the defoliation management trial that tested the effects of harvest interval (21 24, 27 and 35 d) and stubble height (8 and 16cm stubble) on herbage nutritive value lead to the following conclusions:

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68 Across years, total CP concentration was highest at 21 d but lowest at 35 d intervals. In 2008, CP declined as interval between harvests increased beyond 21 d while a decline was only detected at 35d harvests in 2007. No differences were detected due to stubble height in either year. Seasonally, more variability in CP levels was detected in 2008 than in 2007, likely a consequence of the lower soil nutrient levels and more marked water stress conditions in 2008. It should be noted that overall, CP levels were highest in 2007 and decreased only for the longest harvest interval ( 35 d ) further highlighting the benefits of supplying fertilization and irrigation. Phosphor us concentration was affected by harvest intervals i n both years. Nonetheless, levels remained fairly stable and corresponded to values reported in other bermudagrass studies ( Pierzynski and Logan, 1993; Woodard et al., 2007) suggesting a narrow variation of P concentration in herbage tissue. Concerning di gestibility, a stubble height harvest interval interaction trend was present due to differences between stubble heights at the 21d harvest interval. In addition, IVDOM decreased gradually and at similar rates from 21to 35d intervals across years No significant differences were found between stubble heights in either year. In general, t he relatively low variability of IVDOM values observed across harvest intervals and stubble heights suggests that under contrasting growing conditions, Tifton 85 bermudagrass can produce dependably high digestible herb age for lactating dairy cow use. In terms of fiber analysis trends suggest that in creasing harvest interval from 21 to 35 d increases NDF concentrations, which can be expected since with increased maturity more secondary cell wall accumulates. As with IVDOM, no stubble height main

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69 effects were found in either year. Overall, it should also be noted that the magnitude of the increase in NDF concentration across harvest intervals when present, never surpassed 4%, indicating that even when significant differences were found, these were relatively small. This homogeneity throughout the season is an important advantage for producers utilizing Tifton 85 in dairy cow rations; no major adjustments in formulation wou ld need to be made in order to maintain optimum NDF diet levels.

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70 CHAPTER 5 ECONOMIC ANALYSIS OF TIFTON 85 GREENCHOP INCORPORATION INTO DAIRY RATIONS Introduction Dairy production in Florida is centered around confined housing systems, which depend on purchased concentrate feeds and forages to meet the nutritional demands of the herds (Pitman, 2007) Currently, feed ing represents approximately 75% of the operational expenditures of dairies in the state, with an estimated 80% of these costs going into purchased feedstuffs (USDA NASS, 200 9 ). Because of the importance of feeding on dairy profitability, producers are seeking alternative feedstuffs, as well as management and cropping options that can help reduce costs. Hay production in Florida during the warm season months is strongly influenced by the high temperatures and humidity that can negatively affect drying and baling activities, increase dry matter (DM) losses and negatively impact forage nutritive value (Scarborough et al., 2005). Thus, livestock systems that depend on mechanically harvested forages produced onfarm are generally interested in developing alternative forage utilization methods. Harvesting for hay, silage, and haylage allows producers to store forages for feeding at times when her bage availability can be limiting Conserving forage however can be challenging to implement effectively because of forage drying issues under frequent precipitation and the costs involved in establishing and maintaining the infrastructure necessary for si lage or haylage production. A possible alternative is using forages as greenchop which is a management practice where the herbage is mechanically harvested and fed fresh to livestock. This approach can avoid the dry matter and nutritive value losses inher ent in hay or ensiled forages. Additionally, production costs under this management can be lower, not only because of reduced

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71 field losses, but also due to the reduced co sts incurred as less machinery, infrastructure, and their related activities (i.e., baling, storing) are required. To determine the feasibility of using greenchop in the rations for milking herds, the cost of producing greenchop and the feeding requirements of different lactating dairy cows must be considered. While budgets project the inc ome and expenses for a unit of production, such as a hectare of forage for greenchop, least cost ration formulation programs can estimate the combination of forages and other feedstuffs that can minimize feed costs while meeting the requirements of the dai ry animals. These programs can be adapted to different feedstuffs, prices and nutrient profiles, as well as different animal requirements, making them a powerful and dynamic tool for feeding management (Tozer, 2000). The main objective of this analysis was to assess the economic impact of incorporating Tifton 85 bermudagrass greenchop in lactating dairy cow rations. Specific objectives were i) to determine the establishment and production costs of Tifton 85 under different harvest interval practices, and ii ) to determine the least expensive combination of forages, including Tifton 85 greenchop harvest interval scenarios, and concentrate feeds available to producers in the state. The hypothesis of the study is that Florida dairy farmers can reduce the cost of lactating dairy cow rations by utilizing locally harvested, warm season perennial grasses such as Tifton 85 greenchop. Materials and Methods Tifton 85 bermudagrass greenchop p roduc tion c ost In order to develop the production cost of Tifton 85 greenchop, establishment and production budgets were developed. Greenchop management activities differ from

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72 those of hay production, since the herbage is simply harvested and transported fresh to livestock, and no field drying, baling, or storing activities are requir ed. This reduces machinery operating and ownership costs, as well as labor requirements. One difference with this management strategy is that a forage wagon is included in greenchop operations to collect the material that is harvested by the rotary mower. This implement is usually pulled behind the harvesting equipment, or is operated by a truck that runs parallel to the harvester. Within the establishment budget developed, costs of vegetative planting of bermudagrass using above ground stems were obtained from custom operators in North Florida and South Georgia, given that this is an activity that is not frequently done directly by producers. The cost of this activity also is considered in the production budgets, included as a 10yr prorated cost of establ ishment. Thus, the cost of establishing the stand is divided by the expected life of the stand (years) and allocated to the production budgets as fixed costs. This value serves as a base estimate for stand survival of vegetatively propagated bermudagrasses although well maintained stands could last considerably longer. Because of the interest in determining the effects of producing Tifton 85 greenchop under different harvest management options, production budgets were calculated with three, four, and five harvests per season, corresponding to 35, 27 24, and 21d harvest intervals as suggested by the agronomic trial results (Chapters 3 and 4 ). The differences in costs between these different harvest intervals reflect the increased machinery and labor use when more harvests are done.

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73 Determination of machinery c osts Operating and ownership costs for the machinery were estimated using spreadsheet based machinery cost calculator developed by researchers at the University of Minnesota (Lazarus, 2009 ). The spreadsheet uses American Society of Agricultural and Biological Engineer (ASABE) formulas and coefficients to calculate depreciation, maintenance and repair, fuel, insurance, interest and housing costs for the required operations and machines. One important consideration that Lazarus (200 9 ) utilizes in calculating costs is that depreciation is classified as an operating expense, with the justification that to some extent, these costs are userelated since increased usage decreases years of life and potenti al salvage value. Although this approach is somewhat contrasting to traditional cost allocation schemes that considered depreciation to be an exclusively fixed cost (AAA E 2000), it has been adopted widely by extension economists in calculating farming budgets in the United States, such as those of the University of Wisconsin (Schuler, 2005), South Dakota State University (Pflueger, 2005) Iowa State University (Miller et al., 2003) and North Dakota State University (Landblom et al., 2005), among others. In put, land and labor costs used in the spreadsheet are those t hat best reflect conditions in North C entral Florida. These included diesel prices at $ 0.66 per liter (average price for Levy County gas stations in October 2009), and utilizing the average price for unskilled agricultural field workers in Florida at $9. 18 per hour (USDA NASS, 200 9 c). While dairy farm size in Florida is variable (DeVries et al., 2006), area was adjusted to 202 ha (~ 500 acres ) a value that approaches the average pasture and crop a rea reported. Assumptions on time of year and number of passes over each unit area of land varied depending on activity requirement and harvest schedule, and are

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74 specified in each budget. Land rent values were set at $44.46 ha1(~ $ 18 acre1Developing budgets based on results from agronomic t rials ) corresponding to those reported for Florida in 200 9 (USDA NASS, 200 9 ). Additionally, insurance and housing were calculated at 1.5% of average machinery or equipment investment, lubrication costs were estimated at 10% of fuel costs, while no sales tax or inflation rate was included. Fertilization costs used in the study reflect the fertilization management applied during each year of the agronomic trials (Chapter s 3 and 4 ). Thus, 2007 greenchop production budgets included manure application costs to match the 144 kg ha1 of P and 148 kg ha1 of N applied via solid manure and manure irrigation water during the length of the growing season (May to October). In 2008, greenchop production budgets were calculated with no fertilization. While prior applications of manure or commercial fertilizer may have contributed to plant nutrition during the study in both years, they were not included in the fertilization costs because of a l ack of adequate data on the amounts applied and their availability to plants. Establishment fertilization rates were those in the UF IFAS recommendations for bermudagrass (Mylavarapu et al., 2009), that suggest a split application of 112 kg ha1Calculation of m an ure and i rrigation cost for forage production budget of N. Fert ilizer prices used w ere obtained from averages of three retailers in the area of study in November 200 9 and corresponded with $0. 93, $ 0 5 3 and $1.15 per kg of N (average of prices of u rea, a mmonium n itrate and a mmonium sulfate), P ( d iammonium p hosphate) a nd K (uriate of p otash), respectively. Cost of liquid slurry dairy manure application was estimated using the spreadsheet based method developed by Koehler et al. (2009), which incorporates the

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75 variable (i.e. labor, fuel) and fixed costs (machinery depreciation) related to hauling, transporting and spreading manure. Data inputs used reflect the liquid manure applications equivalent to 144 kg ha1 of P and 148 kg ha1 of N during the 2007 season, calculated for 202 ha (~500 acres) of land by rapid broadcast. Since m anure nutrient concentration and availability can vary widely depending on animal factors (i.e. type dairy cow, diet fed, and production level), environmental conditions (i.e. soil type, temperature, soil water status) and manure handling (Van Horn et al., 2003) values were selected from a range of reported values (Zublena et al., 1997) Thus, concentrations of total N, and K2O per 1000 gal were set to 45 2 5 27 with 7080 90 (%) availability coefficients, respectively. Nitrogen and P2O5As with other farming activities, estimation of irrigation costs is highly variable and is best done utilizing actual farm operating and fixed costs. Because of the possible sources of variation and the lack of adequate farm level data to calculate the cost of irrigation during the 2007 season, values were taken from hybrid bermudagrass hay production budgets developed by the University of Georgia ( Lacy and Morgan, 2008), adapted with current fuel ($ 0.66 L coefficients were those estimated for north Florida conditions from producer data by Van Horn et al., (2003) The K availability coefficient was that used by Koehler et al. (2009). 1) and Florida labor costs (9.18 h1Least cost ration linear program m odel ) Irrigation cost was estimated for a center pivot system using a diesel powered pump, applying 127 mm of water per ha during the growing season. To evaluat e the feasibility of incorporating Tifton 85 greenchop in lactating dairy cow rations, a least cost ration linear program model was developed using the Solver

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76 ( 5 1) ( 5 2 ) function of Microsoft Excel. In algebraic terms, the linear program model used had the followin g form: w here Y = ration cost per cow per day, cj = feedstuff j cost, xj = quantity of feedstuff j aij = quantity of nutrient i in ingredient j and h1 = required amount of nutrient i in the ration. The equality or inequality signs are determined by the nutrient of interest. Equation 5 1 represents the objective function of the model, which in our case seeks to minimize the cost of the ration (Y), which is reached by the sum of the product of the quantity and cost of the selected feedstuffs that combined meet a series of nutritional constraints (Equation 5 2) Thus, data inputs to the model can be grouped broadly into: a) lactating dairy cow requirements, b) feedstuff nutritive profile and cost, and c) greenchop nutritive value and cost. In order to test the potential use of greenchop for a wide range of lactating dairy cow nutritional requirements, 12 different scenarios were evaluated, using NRC (2001) nutrient requirements of dairy ca ttle guidelines for 12 lactating Holstein dairy cows, classified by different stages of lactation and production levels : cows in 1st and 3rd lactation, at 60 and 120 d into milk and producing 18, 36 and 54 kg d1 of milk (Table 5 1 ). Thus, the daily dry matter intake (DMI) crude protein (CP), P, Ca, K and net energy for lactation (NE L ) requirements were set as constraints to the model. Maximum allowable limits of CP and P (10% above NRC recommendation), also

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7 7 Table 5 1 Nutritional requirements of lactating Holstein dairy cows used in linear program model Corresponds to 3.5% Fat Corrected Milk with 3% True Protein concentration. Adapted from nutrient requirements of dairy catt le (NRC, 2001) Animal Lactation Age Body Weight Da ys in Milk Milk Production Actual DMI NEL CP diet Ca P K identification # (months) (kg) (d) (kg d -1 ) (kg d -1 ) (Mcal d -1 ) (% DM) (g d -1 ) (g d -1 ) (g d -1 ) 1 1 26 560 42 18 14.4 21.7 15.2 89.3 54.7 194 2 1 26 560 42 36 19.6 34.1 18.8 121.5 74.5 221 3 1 26 560 42 54 24.8 46.5 20.2 153.8 94.2 248 4 1 28 560 110 18 16.6 21.7 14.1 102.9 63.1 194 5 1 28 560 110 36 22.7 34.1 15.2 140.7 86.3 221 6 1 28 560 110 54 28.7 46.5 16.7 177.9 109.1 248 7 3 52 682 42 18 15.9 23.1 15.2 98.6 60.4 198 8 3 52 682 42 36 21.1 35.6 18.8 130.8 80.2 225 9 3 52 682 42 54 26.3 48 .0 20.2 163.1 99.9 252 10 3 54 682 110 18 18.4 23.1 14.1 114.1 69.9 198 11 3 54 682 110 36 24.4 35.6 15.2 151.3 92.7 225 12 3 54 682 110 54 30.5 48 .0 16.7 189.1 115.9 252

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78 were included to avoid excess feeding. Urea was set at a maximum of 1% of ration DM, to avoid nutritional imbalances. Amount of forage in ration was set to a minimum of 30% of the ration for all levels of milk production, while the maximum proportion of forage in diets was set at 70, 60 and 50% for cows producing 18, 36 and 54 kg d1Table 52 Selected constraint levels utilized in linear program model. of milk, respectively. Silage was limited to 60% of the total forage component. Restrictions on maximum amounts of specific concentrate ingredients were incorporated to assure that nutritional constraints are met and to reflect current producer practices in the region (Table 52). Range Constraint (% in diet) Low High Proportion of Forage 3 0 70 Proportion of Silage in Forage c omponent 60 Allowable excess Phosphorus 10 Allowable excess Crude Protein 10 Allowable Urea 1 Soybean hulls 5 Wheat bran 10 Wheat middlings 10 Brewers grains 5 Citrus pulp 10 Gluten feed 10 Corn grains 10 Hominy 12.5 Molasses 5 Maximum proportion of forage in diets was set at 70, 60 and 50% for cows producing 18, 36 and 54 kg d-1 of milk, respectively. Costs of ration ingredients were those quoted for bulk quantities (~905 kg) of readily available feedstuffs in Florida from Suwannee Valley Feeds LLC for November 2009 (Table 53), and include an extra 20% that is estimated for transportation and handling costs. Nutritive value data for feedstuffs were obtained from nutrient

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79 Table 5 3 Prices of readily available feedstuffs to dairy producers in Florida Price Bulk Price on Farm Major feed ingredients ($905 kg -1 ($ kg ) -1 ($ kg ) -1Tifton 85 hay (16.71%CP) ) 8 5 0.0939 0.1127 Alfalfa hay 22 0 0.2431 0.2917 Brewers grains (25% DM) 28 0.0309 0.0371 Citrus pulp 15 2 0.1679 0.201 6 Corn grain 1 85 0.2044 0.2453 Corn gluten feed 1 55 0.171 3 0.2055 Corn silage (33% DM) 45 0.0497 0.059 7 Cottonseed 170 0.187 9 0.2254 Distillers grains 178 0.1967 0.2360 Hominy 1 50 0.165 8 0.1989 Molasses 16 5 0.182 3 0.218 8 Rye silage 8 5 0.0939 0.1127 Sorghum silage (33% DM) 3 2 0.0354 0.0424 Soybean hulls 1 15 0.127 1 0.152 5 Soybean meal 3 60 0.3978 0.477 4 Wheat midds 1 40 0.1547 0.1856 Includes an extra 20% for transportation and handling costs. Prices taken from Suwannee Valley Feeds LLC (November, 2009 ) requirements of dairy cattle (NRC, 2001) tables, and were classified as concentrate, silage, or forage (nonsilage). The final component of the model is that related with the production cost and nutritive value of Tifton 85 greenchop. Data from greenchop defoliation management field trials conducted in 2007 at a North Central Florida dairy sprayfield and in 2008 in an established hayfield were incorporated into the model (Chapters 3 and 4). Treatments in the trial were the combination of two stubble height s (8 and 16 cm) and four harvest intervals (21, 24, 27, and 35 d). Based on results of the trials, budgets were calculated for greenchop production under the four harvest intervals averaged across stubble heights. Thus, the information added to the model w ere yields (kg DM ha1), crude protein concentration (CP; % DM), phosphorus concentration (% DM), net energy

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80 ( 5 3 ) for lactation (NEL; Mcal kg1) and cost ($ kg1NEL Mcal kg1 = 0 0245 TDN(%) 0 12 ) per harvest interval. Crude protein is essential for dairy cow nutrition, since when absorbed from the digestive tract it provides the amino acid building blocks for the synthesis of proteins that are vital to the maintenance, growth, reproduction and lactation of dairy cattle (NRC, 2001). Net energy for lactation is the representation of the energy required for maintenance and milk production of dairy cows. It is calculated as a function of the total digestible nutrients (TDN) of the forage or feedstuff, which in turn depends on the crude protein, ether extract, ash and non fiber carbohydrate fraction (NRC, 2001) The current equation used by NRC (2001) for the estimation of NEL from TDN is as follows: Total diges tible nutrients were not determined analytically for the Tifton 85 samples taken in either 2007 or 2008. Thus, TDN (%) was estimated based on the relationship suggested by Moore (1994), which considers TDN to be numerically equivalent to IVDOM (%) if the ether extract fraction is negligible, as is the case with most tropical forages. Calculated NEL values for harvest interval means are presented in Table 517. Results and Discussion Tifton 85 bermudagrass establishment b udget The budgets formulated for establishment of Tifton 85 for use as greenchop are not different from those developed for other hybrid bermudagrasses. Analyzing the cost structure, it should be noted that most of the expenditures went to planting and fertilization, essentially because of the high costs of inputs (commercial fertilizer and vegetative planting material) and the high machinery requirement for these activities

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81 (Table 54). Overall, planting accounted for approximately 44% of total costs, wh ereas fertilization represented 32%. Th e proportion of total establishment costs allocated to planting and fertilization coincide with those calculated for hybrid bermudagrasses in north Florida in 2006 ( Hewitt 2006) and Georgia in 2008 (Lac y and Morgan, 2008). Producers interviewed at the study sites al so confirmed these findings, highlighting that fertilization and plating related costs are one of the most important items to consider when establishing forages, and further stress the importance of adequate nutrient management and utilization of alternative fertilizer sources. Tifton 85 b er mudagrass greenchop production budgets Overall, when analyzing the activities required to produce hybrid bermudagrasses as greenchop or hay, we find that the former requires less use of machinery and implements than the latter, since after the forage is cut, under greenchop use the material is taken directly to the livestock, whereas when used for hay additional activities must be undertaken in the field to assure the material is adequately dried, baled and stored. Although the comparison may not be entirely justified, since hay can be used at other times when no fresh material is available, harvesting warm season grasses as greenchop could be advantageous, given its lower production costs and apparentl y lower field losses. Comparing production budgets in both years, the costs of producing greenchop in 2007 (Tables 55, 5 7 and 59) were over four times greater than in 2008 (Tables 511, 5 13 and 515), because no fertilizer or irrigation were used. Within each year, the difference in costs between harvest intervals was related solely to the increase or decrease in machinery, labor and associated costs.

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82 Table 5 4 Establishment budget for Tifton 85 bermudagrass using vegetative tops. Activities Month Unit Quantity Unit Cost ($) Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Primary Tillage Disc plow (TD HD 9 m fold) April Pass ha 2.00 1 12.42 24.85 Tractor 360 4WD (313 PTO) April Pass ha 2.00 1 2.99 5.98 Labor April Pass ha 2.00 1 1.33 2.67 Secondary Tillage Leveling disc ( TD 7 m rigid) April Pass ha 2.00 1 5.09 10.18 Tractor 160 MFWD April Pass ha 2.00 1 3.53 7.06 Labor April Pass ha 1.00 1 1.88 1.88 Planting Vegetative material June k g ha 1346 1 0.15 197.60 Planting custom June Pass ha 1.00 1 197.6 0 197.60 Weed control Weedmaster (Dicamba+2,4 D amine) June L 7.56 3.79 28.65 Application (Boom sprayer 15 m ) June Pass ha 1.50 1 10.08 15.12 Tractor 60 HP PTO June Pass ha 2.00 1 1.51 3.01 Labor June Pass ha 2.00 1 0.62 1.24 Fertilization Nitrogen (7 10 d AP ) June kg 33.64 0.93 31.23 Nitrogen (30 d AP) July kg 78.50 0.93 72.86 Phosphorus (P2O5; 7 10 d AP) June kg 44.86 0.75 33.70 Potassium (7 10 d AP) June kg 28.03 1.55 43.37 Potassium (30 d AP) July kg 28.03 1.55 43.37 Lime (includes spreading) June Mt 908.00 0.07 59.28 Fertilizer spreader (12 m ) June July Pass ha 2.00 1 2.03 4.06 Tractor 60 HP PTO June July Pass ha 2.00 1 0.59 1.19 Labor June July Pass ha 2.00 1 1.14 2.27 Total Operating Costs $ 806.22 Ownership Costs Implement Disc Plow ha 1.0 9.48 9.48 Leveling Disc ha 1.0 3.09 3.09 Boom Sprayer 15 m ha 1.0 1.19 1.19 Fertilizer spreader 12 m ha 1.0 1.11 1.11 Tractor Tractor 360 4WD (313 PTO) ha 1.00 3.73 3.73 Tractor 160 MFWD ha 1.00 1.78 1.78 Tractor 60 HP PTO ha 1.00 0.44 0.44 General overhead (10% Op Costs) $ 806.22 0.10 80.62 Total Ownership Costs 101.44 Total Cost (Operative + Ownership costs) 907 .96 Includes spreading, incorporation and firming. Includes interest, insurance and housing. After planting.

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83 Consequently, t his caused the price per unit wei ght of greenchop to vary only from 0.083 to 0.124 $ kg DM1 in 2007 (Tables 56, 5 8 and 510), and from 0.028 to 0.036 $ kg DM1 Least cost linear program model r esults in 200 8 (Tables 512, 514 and 516) As with the case of the establishment budgets, manure fertilization was the activity that had the highest associated costs across harvest intervals in 2007, averaging 30% of total production costs. Irrigation costs were also considerably high, amounting to 18% of total costs It is important to note that calculating costs in 2008 without use of fertilizer or irrigation was done to reflect the experimental conditions from which the agronomic data was obtained, and that reaching comparable yields or nutritive value, and a healthy stand in subsequent years without use of fertilizer would be unlikely. Thus, a gronomic fertilizer prices are important determinants of forage production profitability, and can constitute strong incentives for producers to utilize alternative fertilizer sources, such as cattle manure. Nonetheless, the economic, environmental and agronomic effects of using cattle manure for Tifton 85 nutrition should be studied further. Of special concern are the amounts of P being applied, particularly when manure is appl ied to m eet crop N requirements. Manure applications can be a n important nonpoint source of excess P that can leach and reach bel ow ground water sources; emphasizing the importance of closely monitoring soil nutrient levels, manure nutrient concentration and appl ication methods to ensure that the resource is used as best as possible without causing important environmental impacts. Data on greenchop yield, nutritive value and production cost for both years of the field trials are summarized in Table 517. These values were those used in the model,

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84 Table 5 5 Production costs of Tifton 85 bermudagrass greenchop with 3 harvests per season (35 d interval ) and dairy manure as fertilizer source during 2007. Activities Month Unit Quantity Unit Cost ($) Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Irrigation May October ha mm 127 .00 1.29 164.87 Weed control 2,4 D amine ( 0.48 kg/L ) June L 5.69 2.66 15.12 Application (Boom sprayer 15 m ) June Pass ha 1.00 1 0.35 0.35 Tractor 60 HP PTO June Pass ha 1.00 1 0.62 0.62 Labor June Pass ha 1.00 1 0.89 0.89 Fertilization Manure spreading Custom May Pass ha 1.00 1 256.41 256.41 Harvest Rotary mower/conditioner ( 4 m ) May Sept. Pass ha 3.00 1 1.93 5.78 Tractor (75 HP) May Sept. Pass ha 3.00 1 2.12 6.37 Forage wagon May Sept. Pass ha 3.00 1 0.79 2.37 Labor May Sept. Pass ha 3.00 1 2.64 7.93 Land rent ha 1.00 44.46 44.46 Total Operative Costs $ 522.45 Ownership Costs Implement Rotary mower/conditioner ( 4 m ) ha 1.00 0.61 1.51 Forage wagon ha 1.00 0.13 0.32 Boom Sprayer ( 15 m ) ha 1.00 1.19 1.19 Machinery Tractor (75 HP) ha 1.00 0.59 0.59 Tractor 60 HP PTO ha 1.00 0.44 0.44 Irrigation ha 1.00 222.30 222.30 Establishment Cost (10 yr prorate) ha 0.10 907.96 90.80 General overhead (10% Op. Costs) $ 0.10 522.45 52.25 Total Ownership Costs $ 369.39 Total Production Cost (Operative + Ownership costs) 891.85 Includes interest, insurance and housing. Table 5 6 C ost of DM, crude protein and net energy for lactation using T85 greenchop with 3 harvests per season (35d harvest interval ) during 2007. Harvest Interval (35 d) Total dry matter yield, kg DM ha 1 yr 10800 1 Cost of greenchop, $ kg 1 0.08 3 DM Average cost of CP in greenchop, $ kg 1 0. 459 CP Average cost of Mcal in greenchop, $ kg 1 0.0 7 1 NEL with the cost structure derived from the forage budgets developed for each defoliation interval (21 d with five harvests, 24 and 27 d with four, and 35 d with three). Thus, costs

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85 Table 57. Production costs of Tifton 85 bermudagrass greenchop with 4 harvests per season (24 and 27d interval ) and dairy manure as fertilizer source during 2007. Activities Month Unit Quantity Unit Cost ($) Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Irrigation May October ha mm 127 .00 1.29 164.87 Weed control 2,4 D amine ( 0.48 kg/L ) June L 5.69 2.66 15.12 Application (Boom sprayer 15 m ) June Pass ha 1.00 1 0.35 0.35 Tractor 60 HP PTO June Pass ha 1.00 1 0.62 0.62 Labor June Pass ha 1.00 1 0.89 0.89 Fertilization 0.00 Manure spreading Custom May Pass ha 1.00 1 256.41 256.41 Harvest Rotary mower/conditioner ( 4 m ) May Sept Pass ha 4.00 1 1.53 6.13 Tractor (75 HP) May Sept Pass ha 4.00 1 2.15 8.60 Forage wagon May Sept Pass ha 4.00 1 0.79 3.16 Labor May Sept Pass ha 4.00 1 2.64 10.57 Land rent ha 1.00 44.46 44.46 Total Operative Costs $ 528.46 Ownership Costs Implement Rotary mower/conditioner ( 4 m ) ha 1.00 1.51 1.51 Forage wagon ha 1.00 0.32 0.32 Boom Sprayer ( 15 m ) ha 1.00 1.19 1.19 Machinery Tractor (75 HP) ha 1.00 0.59 0.59 Tractor 60 HP PTO ha 1.00 0.44 0.44 Irrigation ha 1.00 222.30 222.30 Establishment Cost (10 yr prorate) ha 0.10 907.96 90.80 General overhead (10% Operating Costs) $ 0.10 528.46 52.85 Total Ownership Costs $ 369.99 Total Production Cost (Operative + Ownership costs) 898.45 Includes interest, insurance and housing. Table 5 8 C ost of DM, crude protein and net energy for lactation using T85 greenchop with 4 harvests per season (24and 27 d harvest interval ) during 2007. Harvest interval (d ) 24 27 Total dry matter yield, DM yield, kg ha 1 yr 7300 1 8500 Cost of greenchop, $ kg 1 0. 123 DM 0. 10 5 A verage cost of CP in greenchop, $ kg 1 0. 64 4 CP 0. 54 5 Ave rage cost of Mcal in greenchop, $ kg 1 0. 093 NEL 0.0 82 for 2007 were calculated incorporating manure application and irrigation, while those of 2008 used the budgets developed without fertilizer or irrigation. For this reason, within

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86 Table 5 9 Production costs of Tifton 85 bermudagrass greenchop with 5 harvests per season (21 d interval ) and dairy manure as fertilizer source during 2007. Activity Month Unit Quantity Unit Cost ($) Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Irrigation May October ha mm 127 .00 1.29 166.73 Weed control 2,4 D amine ( 0.48 kg/L ) June L 5.69 2.66 15.12 Application (Boom sprayer 15 m ) June Pass ha 1.00 1 0.35 0.35 Tractor 60 HP PTO June Pass ha 1.00 1 0.62 0.62 Labor June Pass ha 1.00 1 0.89 0.89 Fertilization Manure spreading May Pass ha 1.00 1 256.41 256.41 Harvest Rotary mower/conditioner ( 4 m ) May Sept. Pass ha 5.00 1 1.43 7.16 Tractor (75 HP) May Sept. Pass ha 5.00 1 1.75 8.77 Forage wagon May Sept. Pass ha 5.00 1 0.79 3.95 Labor May Sept. Pass ha 5.00 1 2.64 13.21 Land rent ha 1.00 44.46 44.46 Total Operative Costs $ 533.10 Ownership Costs Implement Rotary mower/conditioner ( 4 m ) ha 1.00 1.51 1.51 Forage wagon ha 1.00 0.32 0.32 Boom Sprayer ( 15 m ) ha 1.00 1.19 1.19 Machinery Tractor (75 HP) ha 1.00 0.59 0.59 Tractor 60 HP PTO ha 1.00 0.44 0.44 Irrigation ha 1.00 222.30 222.30 Establishment Cost (10 yr prorate) ha 0.10 907.96 90.80 General overhead (10% Operating Costs) $ 0.10 533.10 53.31 Total Ownership Cost 370.46 Total Production Cost (Operative + Ownership costs) 903.56 Includes interest, insurance and housing. Table 5 10. Cost of DM, crude protein and net energy for lactation using T85 greenchop with 5 harvests per season (21d harvest interval ) during 2007. Harvest Interval (21 d) Total dry matter yield, kg DM ha 1 yr 7300 1 Cost of greenchop, $ kg 1 0. 124 DM Average cost of CP in greenchop, $ kg 1 0. 629 CP Average cost of Mcal in greenchop, $ kg 1 0. 09 1 NEL each scenario, the differences between production costs of defoliation treatments were due to differences in number of harvests and the associated machinery, implement,

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87 Table 511. Production budget for Tifton 85 bermudagrass greenchop with 3 harvests per season (35d harvest interval ) during 2008. Activities Month Unit Quantity Unit Cost ($) Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Weed control 2,4 D amine ( 0.48 kg L 1 June ) L 5.69 2.66 15.12 Application (Boom sprayer 15 m ) June Pass ha 1.00 1 0.35 0.35 Tractor 60 HP PTO June Pass ha 1.00 1 0.62 0.62 Labor June Pass ha 1.00 1 0.89 0.89 Harvest Rotary mower/conditioner ( 4 m ) May Sept. Pass ha 3.00 1 0.78 5.78 Tractor (75 HP) May Sept. Pass ha 3.00 1 0.86 6.37 Forage wagon May Sept. Pass ha 3.00 1 0. 32 2.37 Labor May Sept. Pass ha 3.00 1 1.07 7.93 Land rent ha 1.00 18 .00 44.46 Total Operative Costs $ 101.17 Ownership Costs Implement Rotary mower/conditioner ( 4 m ) ha 1.00 1.51 1.51 Forage wagon ha 1.00 0.32 0.13 Boom Sprayer (15 m) ha 1.00 1.19 1.19 Machinery Tractor (75 HP) Tractor 60 HP PTO ha 1.00 0.59 0.59 ha 1.00 0.44 0.44 Establishment Cost (10 yr prorate) ha 0.10 907.96 90.80 General overhead (10% Op Costs) $ 0.10 101.17 10.12 Total Ownership Costs $ 104.96 Total Production Cost (Operative + Ownership costs) 206.14 Includes interest, insurance and housing. Table 5 12. C ost of DM, crude protein and net energy for lactation using T85 greenchop with 3 harvests per season (35d harvest interval ) during 2008. Harvest Interval (35 d) Total dry matter yield, DM yield, kg ha 1 yr 5700 1 Cost of greenchop, $ kg 1 0.0 36 DM Average cost of CP in greenchop, $ kg 1 0. 26 3 CP Average cost of Mcal in greenchop, $ kg 1 0.0 33 NEL input and labor costs. Results in 2007 suggest that treatments that obtained the highest DM yields in the trial also had the lowest cost per unit weight of greenchop harvested. This appeared

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88 Table 5 13. Production budget for Tifton 85 bermudagrass greenchop with 4 harvests per season (24 and 27 d harvest intervals ) during 2008. Includes interest, insurance and housing. Table 5 14. Cost of DM, crude protein and net energy for lactation using T85 greenchop with 4 harvests per season (24and 27 d harvest interval ) during 2008. Harvest interval (days) 24 27 Total dry matter yield, DM yield, kg ha 1 yr 6600 1 7400 Cost of g reenchop, $ kg 1 0.0 32 DM 0.0 28 A verage cost of CP in greenchop, $ kg 1 0. 21 8 CP 0. 200 Ave rage cost of Mcal in greenchop, $ kg 1 0.0 2 7 NEL 0.02 5 to have a strong effect on the selection of the greenchop treatments to be included in rations W hile nutritional differences among the greenchop treatments were present, the magnitude of the difference does not seem to be biologically important, particularly for cows that are receiving supplements and concentrate feed. Since no fertilization or Activities Month Unit Quantity Unit Cost ($) Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Weed control 2,4 D amine ( 0.48 kg L 1 June ) L 5.69 2.66 15.12 Application (Boom sprayer 15 m ) June Pass ha 1.00 1 0.35 0.35 Tractor 60 HP PTO June Pass ha 1.00 1 0.62 0.62 Labor June Pass ha 1.00 1 0.89 0.89 Harvest Rotary mower/conditioner ( 4 m ) May Sept. Pass ha 4.00 1 1.53 6.13 Tractor (75 HP) May Sept. Pass ha 4.00 1 2.15 8.60 Forage wagon May Sept. Pass ha 4.00 1 0.79 3.16 Labor May Sept. Pass ha 4.00 1 2.64 10.57 Land rent ha 1.00 44.46 44.46 Total Operative Costs $ 107.17 Ownership Costs Implement Rotary mower/conditioner ( 4 m ) ha 1.00 1.51 1.51 Forage wagon ha 1.00 0.32 0.32 Boom Sprayer (15 m) ha 1.00 1.19 1.19 Machinery Tractor (75 HP) ha 1.00 0.59 0.59 Tractor 60 HP PTO ha 1.00 0.44 0.44 Establishment Cost (10 yr prorate) ha 0.10 907.96 90.80 General overhead (10% O p. Costs) $ 0.10 107.17 10.72 Total Ownership Costs $ 105.56 Total Production Cost (Operative + Ownership costs) 212.74

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89 Tabl e 5 15. Production budget for Tifton 85 bermudagrass greenchop with 5 harvests (21 d interval ) per season during 2008. Activities Month Unit Quantity Unit Cost Total Cost $ ha -1 Operative Costs Soil Test April 1.00 17.29 17.29 Weed control 2,4 D amine ( 0.48 kg L 1 June ) L 5.69 2.66 15.12 Application (Boom sprayer 15 m ) June Pass ha 1.00 1 0.35 0.35 Tractor 60 HP PTO June Pass ha 1.00 1 0.62 0.62 Labor June Pass ha 1.00 1 0.89 0.89 Harvest Rotary mower/conditioner ( 4 m ) May Sept. Pass ha 5.00 1 1.25 6.27 Tractor (75 HP) May Sept. Pass ha 5.00 1 1.75 8.77 Forage wagon May Sept. Pass ha 5.00 1 0.79 3.95 Labor May Sept. Pass ha 5.00 1 2.64 13.21 Land rent ha 1.00 44.46 44.46 Total Operative Costs $ 110.93 Ownership Costs Implement Rotary mower/conditioner ( 4 m ) ha 1.00 1.51 1.51 Forage wagon ha 1.00 0.32 0.32 Boom Sprayer (15 m) ha 1.00 1.19 1.19 Machinery Tractor (75 HP) ha 1.00 0.59 0.59 Tractor 60 HP PTO ha 1.00 0.44 0.44 Establishment Cost (10 yr prorate) ha 0.10 907.96 90.80 General overhead (10% O p. Costs) $ 0.10 110.93 11.09 Total Ownership Costs $ 105.94 Total Production Cost (Operative + Ownership costs) 216.87 Includes interest, insurance and housing. Table 5 1 6 C ost of DM, crude protein and net energy for lactation using T85 greenchop with 5 harvests per season (21d harvest interval ) during 2008. Harvest Interval (21 d) Total dry matter yield, kg DM ha 1 yr 6400 1 Cost of greenchop, $ kg 1 DM 0.0 34 1 Average cost of CP in greenchop, $ kg 1 0. 208 CP Average cost of Mcal in greenchop, $ kg 1 0.0 27 NEL irrigation costs occurred in 2008, ration costs of producing milk using Tifton 85 greenchop harvested at different regrowth intervals were very similar and lower in cost than in 2007. In addition, this appears to have made the incorporation of greenchop

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90 T able 5 17. Relevant information from Tifton 85 greenchop field trials and production cost. DM yield (kg ha 1Phosphorus ) (% of DM) CP (% of DM) NEL (Mcal kg 1Cost ) ($ kg 1 DM) Harvest interval (d) 2007 2008 2007 2008 2007 2008 2007 2008 2007 2008 21 7300 6400 0.31 0.30 19.7 16.3 1.36 1.23 0.124 0.034 24 7300 6600 0.31 0.29 19.1 14.8 1.32 1.21 0.123 0.032 27 8500 7400 0.30 0.30 19.4 14.4 1.29 1.17 0.105 0.028 35 10800 5700 0.29 0.27 18.0 13.7 1.16 1.11 0.083 0.036 from lower yielding but higher nutritive value harvest intervals (i.e. 21d intervals) economically feasible. Across all forage types and greenchop regrowth intervals tested in both years, ration cost increased with milk production level (Table 518 ). This was likely due to t he greater DM intake energy and protein requirements of highproducing cows. When all forage options were available in the model without restrictions, the least expensive Tifton 85 greenchop treatment (i.e. harvest interval) was selected above purchas ed Tifton 85 hay or alfalfa hay in both years for all the dairy cow profiles in the study. The likely reason for these sel ections is the considerably lower cost of greenchop DM, energy and protein (Table 51 9 ). Forage DM cost of 21and 24d greenchop treatm ents in 2007 were 10 and 9% greater in cost than purchased Tifton 85 hay, respectively (Table 51 9 ) On the other hand, 27and 35d treatments were 7 and 35% lower in cost than Tifton 85 hay in the same year When compared with purchased alfalfa hay, the most ex pensive greenchop treatment (21 d) was over two times lower in cost. In 2008, all greenchop treatments were lower in cost than either purchased alfalfa or Tifton 85 hays as dietary forage sources Even the most expensive greenchop option (35 d) was

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91 Table 5 18. Average cost of daily rations for lactating dairy cows grouped by production level formulated with different forages. Milk Production Level (kg d 1 ) Forage source (non silage) 18 36 54 ----------($ cow 1 day 1 ) --------T85 greenchop (21d) 2007 1.81 2.84 4.06 2008 1.39 2.36 3.59 T85 greenchop (24d) 2007 1.81 2.84 4.07 2008 1.39 2.36 3.60 T85 greenchop (27d) 2007 1.75 2.77 3.99 2008 1.37 2.35 3.60 T85 greenchop (35d) 2007 1.66 2.68 3.92 2008 1.44 2.44 3.70 Alfalfa 2.51 3.71 5.05 Tifton 85 hay 1.79 2.84 4.11 at least 3 times lower in cost than Tifton 85 hay; with values rising to an 8fold difference in cost when compared to alfalfa hay, under current commodity prices. As a protein source, the highest yielding greenchop regrowth treatment in 2007 (35 d) was 37% lower in cost than Tifton 85 hay and 2.5 times lower in cost than alfalfa hay; while under 2008 conditions, protein provided by greenchop was at least three and e ight times lower in cost than either alfalfa hay or Tifton 85 hay, respectively (Table 519). Nonetheless, care must be taken when balancing rations on CP alone, since this considers all protein sources equal and disregards the actual amounts of metabolizable proteins and essential amino acids (i.e. lysine and methionine) present in feedstuffs. As expected, greenchop provided less NEL per dollar than corn silage during 2007. Even with the very low production costs in 2008, NEL from greenchop was only 33% lower in cost than that in corn silage. Also, across both years and harvest intervals,

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92 Table 51 9 Average cost of forage DM, crude protein and net energy ( NEL ) for lactation in purchased forages and T85 greenchop treatments. Purchased forages T85 greenchop Corn silage Alfalfa hay T85 hay Sorghum Silage ---21 d ------24 d ------27 d ------35 d ---Nutrient 2007 2008 2007 2008 2007 2008 2007 2008 DM, $ kg 1 0.060 0.292 0.112 0.042 0.124 0.034 0.123 0.032 0.105 0.028 0.083 0.036 -------------------------------------$ kg 1 nutrient in kg forage DM --------------------------------Crude Protein 0.72 1.62 0.63 0.47 0.6 3 0. 21 0.64 0. 22 0. 55 0. 20 0. 46 0. 26 NE L 0.04 0.26 0.10 0.04 0.09 0.03 0.09 0.03 0.08 0.0 3 0.07 0.03

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93 purchased alfalfa hay and Tifton 85 hay were more expensive sources of NEL than greenchop (Table 519) These low NEL costs suggests that Tifton 85 bermudagrass greenchop treatments have the potential to at least partially substitute other highquality purchased forages in dairy rations, such as corn silage, alfalfa hay or Tifton 85 hay; coinciding with previous findings by Wes t et al. (1997) and Mandebvu et al. (1998) that suggested that Tifton 85 can be an alternative to using alfalfa hay or corn silage. Greenchop treatments selected by the program in 2007 (35 d) indicate that for dairy production, harvest intervals that maximized DM yields were most profitable for inclusion in dairy rations (Table 520). It is also important to mention that this treatment was generally among the lowest in terms of CP and NEL, although the decline observed in these parameters as harvest intervals increased was generally small (Table 517). This suggests that for formulating rations for lactating dairy cows (under the 2007 cost structure), the small decline in nutritive value at tributed to longer harvest intervals of Tifton 85 greenchop does not offset the greater DM yields obtained, possibly because the rations already include high energy (e.g. corn silage) and protein (e.g. brewers grains) feedstuffs. This hypothesis can be supported by results from dairy grazing trials. When working with heavily supplemented dairy cows, Fontaneli et al (2005) found that T ifton 85 was of equal or superior economic value than pearl millet, a highquality summer annual grass, because of its long er growing season, high DM yields, lower costs and reduced benefits of feeding greater quality forages to cows receiving conce n trates. Also, Fike et al ( 2003) found that cows grazing T ifton 85 pastures produced 29% more milk per unit land area than those grazing rhizoma peanut, a high

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94 Table 5 20. R ation costs of least cost linear program model using Tifton 85 greenchop harvested in 2007 and 2008 growing seasons. Dairy Cow Profile Forage source 1 2 3 4 5 6 7 8 9 10 11 12 Mean ----------------------------------------------($ cow 1 day 1 ) ------------------------------T85 greenchop (21 d) 2007 1.60 2.72 4.00 1.84 2.80 3.96 1.77 2.84 4.13 2.04 3.01 4.14 2.90 2008 1.27 2.30 3.55 1.40 2.27 3.51 1.35 2.41 3.66 1.55 2.45 3.62 2.44 T85 greenchop (24 d) 2007 1.60 2.73 4.01 1.84 2.79 3.97 1.77 2.85 4.14 2.04 3.00 4.14 2.91 2008 1.27 2.31 3.56 1.39 2.28 3.52 1.35 2.41 3.67 1.54 2.43 3.63 2.45 T85 greenchop (27 d) 2007 1.55 2.66 3.94 1.77 2.71 3.90 1.70 2.78 4.06 1.96 2.91 4.04 2.83 2008 1.26 2.30 3.56 1.37 2.28 3.52 1.34 2.41 3.67 1.52 2.41 3.63 2.44 T85 greenchop (35 d) 2007 1.50 2.60 3.87 1.68 2.60 3.83 1.61 2.71 4.00 1.86 2.80 3.96 2.75 2008 1.33 2.40 3.66 1.42 2.37 3.62 1.42 2.51 3.78 1.57 2.48 3.74 2.53 Alfalfa hay 2.27 3.61 4.99 2.53 3.60 4.95 2.43 3.77 5.15 2.80 3.87 5.11 3.76 T85 hay 1.63 2.77 4.06 1.80 2.75 4.02 1.73 2.89 4.19 1.99 2.95 4.15 2.91 and are l owest cost options in 2007 and 2008, respectively

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95 quality summer perennial legume, because of its high dry matter yields tolerance to grazing and high nutritive value. In 2008, greenchop was selected over purchased forage options, although the greenchop treatment selected depended on the production level of the dairy cow (Table 5 21). The model selected greenchop harvested at 27d intervals for cows producing 18 kg milk d1, while rations for cows producing 54 kg milk d1 were formulated using greenchop harvested at 21 d. For the intermediate milk producing level (36 kg milk d1), the model selected 21d greenchop as the most feasible alternative for all profiles except for profile 11, which refers to 3rdOverall, average ration cost for high producing cows (54 kg d lactation cows at 110 days into milk production. Overall, t he results suggest that because of the low production costs of Tifton 85 bermudagrass during 2008, the higher nutritive value of greenchop harvested at 21 d offset its slightly higher DM costs (+ $0.006) compared to the lowest cost harvest interval, 27 d. 1 of milk) when greenchop was included ranged from $3.60 to $4.07 cow1 day1 (average = $3.79), resulting in an average cost reduction of 25 and 8% when compared to rations formulated using purchased alfalfa hay or Tifton 85 hay, respectively (Table 518 ). In addition, ration costs for low producing cows (18 kg d1The reductions in ration costs observed are important for dairy profitability in Florida, since rising feed costs have been identified as one of the mos t important issues currently facing dairy producers in the state (Giesy et al., 2008). Currently, feed of milk), were lowered on average by 52 and 12% by using greenchop instead of alfalfa or Tifton 85 hay, respectively.

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96 Table 521. R ation profile and costs of least cost linear program model using Tifton 85 greenchop harvested in 2008 for selected cow profiles Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 T85 greenchop (21 d) 36.0 30.0 36.0 30.0 36.0 30.0 30.0 T85 greenchop (27 d) 42.0 42.0 42.0 42.0 36.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 10.0 10.0 10.0 10.0 Gluten feed 2.3 1.7 2.5 2.4 2.3 2.3 2.4 2.4 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Cotton seed 0.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.2 0.1 0.1 0.2 0.2 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 69.1 70.6 72.0 69.1 70.7 72.0 69.1 70.6 71.9 69.1 70.6 72.0 NEL (Mcal) 21.7 34.1 46.5 23.6 34.1 46.5 23.1 35.6 48.0 26.2 36.1 48.0 Calcium 0.78 0.62 0.72 0.80 0.65 0.74 0.79 0.62 0.72 0.80 0.65 0.75 Phosphorus 0.36 0.36 0.34 0.38 0.38 0.36 0.37 0.36 0.35 0.38 0.38 0.37 Potassium 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 Ration cost $ day -1 cow 1 1.26 2.30 3.55 1.37 2.27 3.51 1.34 2.41 3.66 1.52 2.41 3.62 Except NEL that is measured as Mcal. represents approximately 75% of operational costs, with an estimated 80% going into purchased feedstuffs (USDA NASS, 2009b). Thus, any reductions in this important component of the farming system can translate into large economic gains for producers, if animal health, milk yield and quality are not affected. Conclusions and Recommendations Tifton 85 greenchop production is a forage management practice that requires fewer management practices than harv esting for hay or silage production. This

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97 translates into lower production costs, since less machinery, inputs and labor are required. From an agronomic perspective, fewer yield losses can be expected under this form of utilization, since the forage is not left to dry in the field, as in hay production, or placed in silos or other structures for preservation for further use. While the comparison between haying and ensiling and greenchop may not be justified completely since they can have different purposes in feeding management, harvesting Tifton 85 bermudagrass as greenchop is a potentially attractive alternative during the summer growing season. In terms of production cost (per unit of DM weight), differences existed between the budgets calculated with di fferent harvest intervals. Overall, more harvests imply more machinery, input and labor costs, and not always lead to increased yields or biologically significant differences in nutritive value. Also, given the high proportion of costs that go into fertili zation, the source (manure vs. inorganic fertilizer) can be an important consideration for producers wishing to maximize the use of the resources at their dispos al to reduce feeding costs. With the lower production costs and high nutritive value that can be obtained with managing Tifton 85 as greenchop, it is not surprising that its use can reduce the cost of formulating rations for lactating dairy cows. This is mainly due to its high DM production and nutritive value, which make it a relatively inexpensiv e source of energy for lactation and protein, compared to other widely used purchased forage options. In addition, greater amounts of forage can be fed to dairy cows using Tifton 85 greenchop than with the other alternatives in the study, suggesting that t his forage management practice can be a viable alternative in Florida dairies.

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98 Further research is warranted, particularly to understand the long term effects of this management on stand persistence, as well as evaluating the effects of fertilizer source. Animal trials would also be critical to determine if high milk production levels can be sustained using rations formulated with significant proportions of Tifton 85 greenchop since previous research has show that silage from bermudagrass harvested at 35 d regrowth intervals can reduce milk yields compared to cows fed elephantgrass silage or corn silage (Ruiz et al., 1995) Also, comparative economical analysis of this forage use should be made with other cropping systems and feeding alternatives.

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99 CHAPTER 6 SUMMARY AND CONCLUSI ONS Defoliation management of forages is one of the most important activities that producers control to obtain high yields and quality. Harvest interval and stubble height are known to affect the accumulation of DM, the herbage nutrit ive value and the stand persistence of hybrid bermudagrasses, but more information is needed to help guide harvest management practices for producers in Florida. Thus, studies were conducted during 2007 and 2008 to determine the effects of harvest interval and stubble height on DM yields, soil N and P removal and herbage nutritive value of Tifton 85 bermudagrass. In addition, a least cost ration formulation linear program was developed in order to assess the economic impact of incorporating Tifton 85 greenc hop in lactating dairy cow rations. In terms of DM yields, year by stubble height and year by harvest interval interactions were detected. Across years, the 8 cm stubble height produced more DM than the 16 cm level, although this difference was greater un der the water and N restricted conditions in 2008, where the short stubble produced 30% more DM than the tall stubble, compared to a 9% difference between heights in 2007. In 2007, total yields were consistently greater as the harvest interval was reduced from 21 to 35 d (linear effect) suggesting that longer periods between harvests maximize DM yields. In contrast, during 2008 yields showed a cubic response to harvest interval with the highest values observ ed for 27 d and lowest under 35d intervals. Al so, DM yields varied throughout the year in response to varying environmental conditions. Overall, greater yields were typically present when conditions were most conducive to vegetative growth, particularly in terms of water availability. While harvest

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100 ev ent stubble height interactions were present in both years, the differences between stubble heights for a given harvest event tended to be of a lower magnitude in 2007 than in 2008. In addition, DM yields obtained by leaving 16cm stubble tended to be mo re consistent throughout the season, possibly suggesting a management that may be more beneficial for producers, because of greater dependability of yields. Removal of N and P was highest for treatments with high DM yields in both years Consequently, 35and 27 d harvests removed the most N and P in 2007 and 2008, respectively. Stubble height main e ffects were found for N and P removal with shorter stubble heights removing more N and P Furthermore, 35d harvests in 2007 removed 22% of applied P and 2.1 times as much N as was applied in either manure or manure irrigation water, suggesting that Tifton 85 can be a an important tool for phytoremediation in dairy sprayfields. Across both years of the study, herbage nutritive value tended to decline with long er harvest intervals, while appearing to be fairly homogenous between the stubble heights tested, even when grown under contrasting fertilization and soil moisture regimes. Also, total crude protein concentration was lowest at 35 d intervals, although valu es dropped only after 27 d in 2007, while in 2008 the decline began after 21d harvests. Seasonally, more variability in CP concentrations was detected in 2008 than in 2007, likely a consequence of the lower soil nutrient levels and more marked water stres s conditions. It also should be noted that overall, CP concentrations were highest under 2007 conditions than in 2008, further highlighting the benefits of supplying fertilization and irri gation. In relation to phosphor us concentration, although differences were found among harvest intervals in both years concentrations remained fairly stable,

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101 and corresponded to values reported in other bermudagrass studies. Concerning digestibility, IVDOM decreased linearly and at sim ilar rates from 21to 35d intervals in both years. Nonetheless, the decline in digestibility between these harvest intervals did not surpass 11% Additionally, no differences were found between stubble heights in either year. Although some harvest events stubble height interactions were detected within harvest interval the variation in digestibility was relatively low for the most part In general, IVDOM w as greater and more stable in 2007, suggesting that greater nutrient availability and better soil moisture f avor forage digestibility. Also the low variability observed across stubble heights and harvest intervals throughout the season suggests that across different growing conditions, Tifton 85 bermudagrass can produce dependably highly digestible her bage that could help meet the nutritional requirements of lactating dairy cows. Neutral detergent fiber concentrations increased with decreasing harvest interval from 21 to 35 d and were greater for 16cm stubble than 8cm stubble at 21d harvests While the reasons for the difference between stubble heights at 21d harvests is unclear, the differences among harvest intervals could be explained by a greater accumulation of secondary cell wall components, a larger proportion of senescing or dead material, or a reduction in leaf to stem ratio with the onset of maturity Overall, the increase in NDF concentration with longer harvest intervals when present, was relatively small. This homogeneity between intervals can be an important advantage for producers ut ilizing Tifton 85 in lactating dairy cow rations, since no major adjustments in formulation would need to be made in order to maintain optimum NDF diet

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102 concentrations although the NEL concentration will likely decline between 21and 35 d intervals. When compared to other harvest options, greenchop production requires fewer activities than harvesting for hay or silage production. This translates into lower production costs, since less machinery, inputs and labor are required. Also feeding freshly cut forage avoids the yield losses associated with conserved forages. However, utilizing forages as greenchop does little to solve forage availability issues in seasons of low forge production. Nonetheless, Tifton 85 bermudagrass used as greenchop is a potentially attractive alternative during the summer growing season. In terms of production cost s (per unit weight), more harvests per season resulted in more machinery, input and labor costs, and did not always result in significant improvements in nutritive value. Also, given the high proportion of costs that go to supplying crop nutrients, the source of fertilizer can be an important consideration for producers wishing to lower production costs Producers should take advantage of the readily available manure. Comp ared to the purchased forage options available to producers in the state based on 2009 prices incorporating onfarm grown Tifton 85 greenchop can reduce ration costs for a wide range of lactating dairy cows. This is mainly due to its high DM production and nutritive value, which make it a relatively inexpensive source of energy and protein for lactation, suggesting that this forage management practice can be a viable alternative in Florida dairies.

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103 Dairymen could potentially decrease feeding cost by substituting a portion of the rations with onfarm grown Tifton 85 greenchop, and in the process reduce nutrient inputs and remove excess N and P from dairy sprayfields.

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104 APPENDIX RESULTS OF LEAST COST RATIONS FORMULA TED WITH TIFTON 85 BERMUDAGRAS S GREENCHOP HARVESTED AT DIFFERENT HARVE ST INTERVALS Table A 1 Ingredients and costs of rations formulated for selected lactating dairy cows usin g T85 greenchop harvested at 21d intervals (2007) Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 T85 greenchop (21 d) 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 2.3 10.0 2.4 10.0 2.3 10.0 2.4 8.6 Gluten feed 2.2 2.4 2.2 3.8 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 70.7 72.0 73.0 70.7 72.1 73.1 70.7 72.0 73.0 70.7 72.1 73.1 NEL (Mcal) 21.9 34.1 46.5 25.2 35.4 46.5 24.1 35.6 48.0 27.9 38.1 48.6 Calcium 0.62 0.56 0.54 0.62 0.62 0.61 0.62 0.57 0.55 0.62 0.62 0.62 Phosphorus 0.40 0.37 0.32 0.40 0.42 0.38 0.40 0.39 0.33 0.40 0.42 0.42 Potassium 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.28 Ration cost $ day -1 cow 1 1.60 2.72 4.00 1.84 2.80 3.96 1.77 2.84 4.13 2.04 3.01 4.14 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactation, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lact ation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 110 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1.

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105 Table A 2. Ingredients and costs of rations formulated for selected lactating dairy cows u sing T85 greenchop harvested 24d intervals (2007) Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 T85 greenchop (24 d) 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 2.3 10.0 2.4 10.0 2.3 10.0 2.4 8.5 Gluten feed 2.2 2.4 2.2 3.8 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 70.7 72.0 73.0 70.7 72.1 73.1 70.7 72.0 73.0 70.7 72.1 73.1 NEL (Mcal) 21.7 34.1 46.5 25.1 35.3 46.5 24.0 35.6 48.0 27.8 37.9 48.4 Calcium 0.62 0.55 0.54 0.62 0.62 0.61 0.62 0.57 0.55 0.62 0.62 0.62 Phosphorus 0.40 0.37 0.32 0.40 0.42 0.37 0.40 0.38 0.33 0.40 0.42 0.42 Potassium 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.28 Ration cost $ day -1 cow 1 1.60 2.73 4.01 1.84 2.79 3.97 1.77 2.85 4.14 2.04 3.00 4.14 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactation, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Hols tein in 3rd lactation, at 110 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1.

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106 Table A 3 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 27d intervals (2007) Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 T85 greenchop (27 d) 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 2.3 10.0 2.4 10.0 2.3 10.0 2.4 8.5 Gluten feed 2.2 2.4 2.2 3.8 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 70.7 72.0 73.0 70.7 72.1 73.1 70.7 72.0 73.0 70.7 72.1 73.1 NEL (Mcal) 21.7 34.1 46.5 24.9 35.1 46.5 23.9 35.6 48.0 27.6 37.7 48.2 Calcium 0.62 0.55 0.54 0.62 0.62 0.61 0.62 0.57 0.56 0.62 0.62 0.62 Phosphorus 0.39 0.37 0.32 0.39 0.42 0.37 0.39 0.38 0.33 0.39 0.42 0.42 Potassium 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.28 Ration cost $ day -1 cow 1 1.55 2.66 3.94 1.77 2.71 3.90 1.70 2.78 4.06 1.96 2.91 4.04 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactat ion, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 11 0 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1

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107 Table A 4 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 35d intervals (2007). Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 T85 greenchop ( 35 d) 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 2.3 10.0 2.4 10.0 2.3 10.0 2.4 10.0 Gluten feed 2.2 2.4 2.2 2.4 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 70.7 72.0 73.0 70.7 72.1 73.1 70.7 72.0 73.0 70.7 72.1 73.1 NEL (Mcal) 21.7 34.1 46.5 24.4 34.5 46.5 23.4 35.6 48.0 27.1 37.1 48.0 Calcium 0.60 0.54 0.54 0.62 0.62 0.60 0.62 0.56 0.55 0.62 0.62 0.62 Phosphorus 0.38 0.36 0.32 0.39 0.42 0.37 0.39 0.38 0.32 0.39 0.42 0.38 Potassium 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 Ration cost $ day -1 cow 1 1.50 2.60 3.87 1.68 2.60 3.83 1.61 2.71 4.00 1.86 2.80 3.96 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactat ion, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 11 0 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1

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108 Table A 5 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 21d intervals (2008). Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 T85 greenchop ( 21 d) 42.0 36.0 30.0 42.0 36.0 30.0 42.0 36.0 30.0 42.0 36.0 30.0 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 10.0 0.0 1 0.0 10.0 10.0 Gluten feed 2.3 1.7 2.5 2.4 2.3 2.3 2.5 2.4 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.2 0.2 0.1 0.2 0.2 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 69.1 70.6 72.0 69.2 70.7 72.0 69.1 70.6 71.9 69.2 70.7 72.0 NEL (Mcal) 21.7 34.1 46.5 24.1 34.1 46.5 23.1 35.6 48.0 26.7 36.7 48.0 Calcium 0.79 0.62 0.72 0.80 0.65 0.74 0.80 0.62 0.72 0.80 0.65 0.75 Phosphorus 0.37 0.36 0.34 0.38 0.38 0.36 0.38 0.36 0.35 0.38 0.38 0.37 Potassium 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 Ration cost $ day -1 cow 1 1.27 2.30 3.55 1.40 2.27 3.51 1.35 2.41 3.66 1.55 2.45 3.62 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactat ion, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 11 0 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1

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109 Table A 6 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 24d intervals (2008). Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 T85 greenchop ( 24 d) 42.0 36.0 30.0 42.0 36.0 30.0 42.0 36.0 30.0 42.0 36.0 30.0 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 1 0.0 10.0 10.0 10.0 Gluten feed 2.3 2.0 2.4 2.4 2.3 2.2 2.4 2.4 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 69.1 70.6 71.9 69.1 70.6 72.0 69.1 70.6 71.9 69.1 70.6 72.0 NEL (Mcal) 21.7 34.1 46.5 23.9 34.1 46.5 23.1 35.6 48.0 26.5 36.4 48.0 Calcium 0.79 0.62 0.72 0.81 0.65 0.74 0.81 0.62 0.72 0.81 0.66 0.76 Phosphorus 0.36 0.35 0.34 0.38 0.38 0.36 0.38 0.35 0.34 0.38 0.38 0.37 Potassium 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 Ration cost $ day -1 cow 1 1.27 2.31 3.56 1.39 2.28 3.52 1.35 2.41 3.67 1.54 2.43 3.63 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactat ion, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 11 0 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1

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110 Table A 7 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 27d intervals (2008). Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 28.0 24.0 20.0 T85 greenchop ( 27 d) 42.0 36.0 30.0 42.0 36.0 30.0 42.0 36.0 30.0 42.0 36.0 30.0 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 0.4 10.0 10.0 10.0 10.0 Gluten feed 0.0 1.9 0.5 0.0 2.4 2.4 0.0 2.3 2.2 0.0 2.4 2.4 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 69.1 70.6 72.0 69.1 70.6 72.0 69.1 70.6 71.9 69.1 70.6 72.0 NEL (Mcal) 21.7 34.1 46.5 23.6 34.1 46.5 23.1 35.6 48.0 26.2 36.1 48.0 Calcium 0.78 0.63 0.72 0.80 0.64 0.73 0.79 0.62 0.72 0.80 0.65 0.75 Phosphorus 0.36 0.35 0.34 0.38 0.37 0.36 0.37 0.36 0.35 0.38 0.38 0.37 Potassium 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 1.56 1.47 1.39 Ration cost $ day -1 cow 1 1.26 2.30 3.56 1.37 2.28 3.52 1.34 2.41 3.67 1.52 2.41 3.63 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactat ion, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 11 0 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1

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111 Table A 8 Ingredients and costs of rations formulated for selected lactating dairy cows using T85 greenchop harvested 35d intervals (2008). Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 28.0 24.0 32.5 28.0 24.0 32.5 28.0 24.0 32.5 28.0 24.0 32.5 T85 greenchop ( 35 d) 42.0 36.0 17.5 42.0 36.0 17.5 42.0 36.0 17.5 42.0 36.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 2.3 10.0 10.0 2.1 10.0 10.0 Gluten feed 2.2 2.4 2.3 0.2 2.2 2.4 2.3 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 4.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.2 0.1 0.2 0.3 0.1 0.2 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 69.1 70.7 73.0 69.1 70.6 73.1 69.1 70.7 73.0 69.1 70.6 73.1 NEL (Mcal) 21.7 34.1 46.5 23.2 34.1 46.5 23.1 35.6 48.0 25.7 35.6 48.0 Calcium 0.79 0.67 0.54 0.82 0.65 0.60 0.80 0.66 0.55 0.82 0.66 0.62 Phosphorus 0.35 0.33 0.31 0.38 0.37 0.36 0.37 0.33 0.32 0.38 0.38 0.37 Potassium 1.56 1.46 1.27 1.56 1.47 1.27 1.56 1.46 1.27 1.56 1.47 1.27 Ration cost $ day -1 cow 1 1.33 2.40 3.66 1.42 2.37 3.62 1.42 2.51 3.78 1.57 2.48 3.74 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactat ion, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lactation, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 11 0 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1.

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112 Table A 9 Ingredients and costs of rations formulated for selected lactating dairy cows using alfalfa hay Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 Alfalfa hay 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 1.8 5.9 2.4 6.5 1.9 6.0 2.4 6.6 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 9.9 12.5 12.5 5.0 12.5 12.5 4.9 12.5 12.5 5.0 12.5 12.5 Cotton seed 0.5 6.4 5.9 0.4 6.3 5.8 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 0.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.2 0.1 0.1 0.1 0.2 0.2 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 68.7 69.9 71.2 68.2 70.0 71.3 68.2 69.9 71.2 68.2 70.0 71.3 NEL (Mcal) 21.7 34.1 46.5 24.2 34.3 46.5 23.2 35.6 48.0 26.8 36.8 48.0 Calcium 0.64 0.54 0.52 0.63 0.62 0.60 0.63 0.55 0.53 0.63 0.62 0.62 Phosphorus 0.37 0.36 0.35 0.38 0.42 0.40 0.38 0.37 0.36 0.38 0.42 0.41 Potassium 1.37 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 Ration cost $ day -1 cow 1 2.27 3.61 4.99 2.53 3.60 4.95 2.43 3.77 5.15 2.80 3.87 5.11 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactation, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lacta tion, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 110 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1.

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113 Table A 10 Ingredients and costs of rations formulated for selected lactating dairy cows using purchased Tifton 85 hay Cow profile Ingredients 1 2 3 4 5 6 7 8 9 10 11 12 Forage -------------------------------------% in ration ---------------------------------Corn s ilage 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 45.5 39.0 32.5 Tifton 85 hay 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 24.5 21.0 17.5 Total forage in ration 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 70.0 60.0 50.0 Concentrate Brewers grain 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Citrus pulp 2.3 10.0 2.4 10.0 2.3 10.0 2.4 10.0 Gluten feed 2.2 2.4 2.2 2.4 Corn grains 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Hominy 9.9 12.5 12.5 5.0 12.5 12.5 5.2 12.5 12.5 5.0 12.5 12.5 Cotton seed 0.5 6.4 5.9 0.4 6.3 5.8 Soybean hulls 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Wheat middlings 5.0 5.0 5.0 5.0 5.0 4.7 5.0 5.0 5.0 5.0 5.0 Urea 0.1 0.2 0.3 0.1 0.1 0.1 0.2 0.3 0.1 0.1 Total Concentrate 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 30.0 40.0 50.0 Ration Nutritive Profile Crude p rotein 15.2 18.8 20.2 14.1 15.2 16.7 15.2 18.8 20.2 14.1 15.2 16.7 TDN 71.2 72.0 73.0 70.7 72.1 73.1 70.7 72.0 73.0 70.7 72.1 73.1 NEL (Mcal) 21.7 34.1 46.5 24.1 34.2 46.5 23.1 35.6 48.0 26.7 36.7 48.0 Calcium 0.60 0.54 0.54 0.62 0.62 0.60 0.62 0.55 0.55 0.62 0.62 0.61 Phosphorus 0.37 0.36 0.32 0.39 0.42 0.36 0.39 0.37 0.32 0.39 0.42 0.37 Potassium 1.37 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 1.39 1.32 1.27 Ration cost $ day -1 cow 1 1.63 2.77 4.06 1.80 2.75 4.02 1.73 2.89 4.19 1.99 2.95 4.15 Except NEL that is measured as Mcal. Cow 1 is a Holstein in 1st lactation, at 42 days in milk producing 18 kg milk d-1; Cow 2 is a Holstein in 1st lactation, at 42 days in milk producing 36 kg milk d-1; Cow 3 is a Holstein in 1st lactation, at 42 days in milk producing 54 kg milk d-1; Cow 4 is a Holstein in 1st lactation, at 110 days in milk producing 18 kg milk d-1; Cow 5 is a Holstein in 1st lacta tion, at 110 days in milk producing 36 kg milk d-1; Cow 6 is a Holstein in 1st lactation, at 110 days in milk producing 54 kg milk d-1; Cow 7 is a Holstein in 3rd lactation, at 42 days in milk producing 18 kg milk d-1; Cow 8 is a Holstein in 3rd lactation, at 42 days in milk producing 36 kg milk d1; Cow 9 is a Holstein in 3rd lactation, at 42 days in milk producing 54 kg milk d-1; Cow 10 is a Holstein in 3rd lactation, at 110 days in milk producing 18 kg milk d-1; Cow 11 is a Holstein in 3rd lactation, at 110 days in milk producing 36 kg milk d-1; Cow 12 is a Holstein in 3rd lactation, at 110 days in milk producing 54 kg milk d-1.

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125 BIOGRAPHICAL SKETCH Jos Alejandro Clavijo Michelangeli (a.k a. Pepe) was born in the town of Maracay n orth central Venezuela in 1982. He spent his early years living in Montreal, Canada from 1986 to 1991 and Gainesville, FL from 1995 to 1996 with his family. He settled back in his hometown to finish middle and high school at the Unidad Educativa Calicantina, graduating in the 2000 class. That same year he began his undergraduate degree as an Agronomical Engineer at the Universidad Central de Venezuela. As an undergraduate, he was a teaching assistant in Statistics and Experimental Design, an ecotourism guide working for national and international birdwatching companies, an intern in an environmental consulting agency and a cattle ranching consortium, and an assistant in several research programs spanning molecular biology, ento mology and ornithology. Upon graduation in 2006, he continued to work in ecotourism and ornithology research until he began his Master of Science degree in agronomy at the University of Florida in January 2008, under the mentorship of Dr. Yoana Newman. During this time, he has been a research assistant in the forage extension program, and participated as a student research assistant in the Ornithology Laboratory of the Florida Museum of Natural History during 2008. Upon completing his MSc degree, Pepe will pursue a PhD degree focusing on natural resource policy. After his graduate studies, he plans on working for governments or nongovernment organizations developing sustainable landuse policies for developing nations.