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1 EFFECTS OF ALUMINUM FROM WATER TR EATMENT RESIDUAL APPLICATIONS TO PASTURES ON MINERAL STATUS OF GRAZING CA TTLE AND MINERAL CONCENTRATIONS OF FORAGES By RACHEL KRISTIN PRATT A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007
2 2007 Rachel Pratt
3 ACKNOWLEDGEMENTS I express my sincere gratitude to Dr. Lee McDowell for his support as the chairman on my committee. His wisdom broadened my understa nding of animal nutrition and his guidance and friendship were priceless. I also acknow ledge Dr. George OConnor for his time on my supervisory committee and to his team for helping with preparation of data. I also thank Dr. Adegbola Adesogan for his time and advice as a member of my supervisory committee. Special thanks are due to Na ncy Wilkinson for her friendshi p, patience, and assistance in the lab, and to Jan Kivipelto and Pamela Mile s who graciously shared their time and knowledge to show me laboratory techniques. Thanks are al so due to Bert Faircloth and his team at the Santa Fe Beef Research Facility for their help with the care of the cattle and with the sample collections. I also thank Megan Brennan for her help with the statistics, Paul Davis and Jerry Wasdin for their help at the start of the study, and Tara Fe lix, for her help in the lab. Finally, I am grateful to my husband and best friend, Theodore Madison, for all of the hard work, dedication, and support that he has given me throughout th is endeavor. His love and encouragement during even the hardest times al lowed me to succeed during the pursuit of this degree.
4 TABLE OF CONTENTS page ACKNOWLEDGEMENTS.............................................................................................................3 LIST OF TABLES................................................................................................................. ..........6 ABSTRACT....................................................................................................................... ..............7 CHAPTER 1 INTRODUCTION................................................................................................................... .9 2 LITERATURE REVIEW.......................................................................................................11 The History of Phosphorus.....................................................................................................11 Phosphorus Metabolism and Requirements............................................................................12 Phosphorus Deficiencies........................................................................................................ .15 Phosphorus Impact on the Land.............................................................................................16 Calcium........................................................................................................................ ...........17 Magnesium...................................................................................................................... .......19 Alumin um....................................................................................................................... ........20 Interactions Between Al and P...............................................................................................23 Water Treatment Residuals.....................................................................................................24 The Pros and Cons of Al-WTR..............................................................................................26 3 EFFECTS OF ALUMINUM FROM WATER TREATMENT RESIDUAL APPLICATIONS TO PASTURES ON MINERAL STATUS OF GRAZING CATTLE AND MINERAL CONCENTRATIONS OF FORAGES......................................................31 Introduction................................................................................................................... ..........31 Materials and Methods.......................................................................................................... .32 Experiment 1 (2005)........................................................................................................32 Experiment 2 (2006)........................................................................................................35 Results and Discussion......................................................................................................... ..36 Performance Results (Experiment 1)...............................................................................36 Performance Results (Experiment 2)...............................................................................36 Performance Discussion..................................................................................................38 Plasma Mineral Results (Experiment 1)..........................................................................38 Plasma Mineral Results (Experiment 2)..........................................................................40 Plasma Mineral Discussion.............................................................................................42 Liver Mineral Results (Experiment 1).............................................................................45 Liver Mineral Results (Experiment 2).............................................................................45 Liver Mineral Discussion................................................................................................47 Bone Mineral Results (Experiment 1).............................................................................47 Bone Mineral Results (Experiment 2).............................................................................49 Bone Mineral Discussion................................................................................................49
5 Forage Mineral Results (Experiment 1)..........................................................................49 Forage Mineral Results (Experiment 2)..........................................................................54 Forage Mineral Discussion..............................................................................................55 Summary and Conclusions.....................................................................................................59 APPENDIX CHEMICAL COMPOSITION OF FORAGES.......................................................62 LIST OF REFERENCES................................................................................................................63 BIOGRAPHICAL SKETCH.........................................................................................................72
6 LIST OF TABLES Table page 3-1 Effect of Aluminum-Water Treatment Residuals (Al-WTR) and P supplementation on Experiment 1 Steer Body Weights (kg)........................................................................373-2 Effect of Aluminum-Water Treatment Residuals (Al-WTR) and P supplementation on Experiment 2 Steer Body Weights (kg)........................................................................393-3 Plasma mineral concentrations as affected by Al-WTR and P supplementation (Experiment 1)................................................................................................................. ..413-4 Plasma mineral concentrations as affected by Al-WTR and P supplementation (Experiment 2)................................................................................................................. ..433-5 Liver Al, Cu, and P concentrations (DMB ) as affected by Al-WTR application to pastures and P supplementation (Experiment 1)................................................................463-6 Liver Al, Cu, and P concentrations (DMB ) as affected by Al-WTR application to pastures and P supplementation (Experiment 2)................................................................483-7 Effects of Al-WTR and P supplementati on on bone mineral concentrations (ash basis) of Ca, P, Mg, and Al (Experiment 1).......................................................................503-8 Effects of Al-WTR and P supplementati on on bone mineral concentrations (ash basis) of Ca, P, Mg, and Al (Experiment 2).......................................................................503-9 Forage minerals as affected by wa ter treatment residuals (Experiment 1)........................523-10 Forage minerals as affected by wa ter treatment residuals (Experiment 2)........................56A-1 Chemical composition of bahiagrass wit hout Al-WTR application for Experiments 1 and 2.......................................................................................................................... .........62
7 Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EFFECTS OF ALUMINUM FROM WATER TR EATMENT RESIDUAL APPLICATIONS TO PASTURES ON MINERAL STATUS OF GRAZING CA TTLE AND MINERAL CONCENTRATIONS OF FORAGES By Rachel Kristin Pratt December 2007 Chairman: Lee McDowell Major: Animal Sciences Amorphous aluminum hydroxides applied to the la nd in the form of drinking water treatment residuals (Al-WTR) can reduce soluble P con centrations in soils and thus can reduce P contamination of the environment. Two experi ments each using 36 grazing Holstein steers were conducted to determine the effects of Al-WTR pasture applications on the mineral status (principally P) and performance of cattle. A second objective was to evaluate the effects of the applied Al-WTR on bahiagrass ( Paspalum notatum ) mineral concentrations. The treatments were replicated 3 times each and were as follows: 1) controlno Al-WTR a pplication with steers receiving free-choice mineral supplement without P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-W TR, and 4) treatment 2 with Al-WTR. Total application of Al-WTR over two years was 75.8 Mg dry weight/h a on the pastures. The major minerals in Al-WTR are 7.8% Al, 0.73% S, 0.30% P and 0.30% Fe. There were no differences (P>0.05) in body weight gain among treatments fo r experiment 1, but for experiment 2, cattle subjected to the Al-WTR treatment without supp lemental P had higher av erage final body weight (P<0.05) than the control treatment that receive d supplemental P (241 vs. 218 kg). In general,
8 there were few treatment effects on mineral concen trations in plasma, liver, and bone. Forage mineral concentrations for both years were gene rally unaffected by treatment but were affected (P<0.05) by collection dates (approximately ever y 28 days throughout the experiment). Most forage samples were deficient in Na, Cu, Se, and Co. At various collection dates, forages were deficient in Ca, P, Fe, and Zn. Forage con centrations of K and Mn were above cattle requirements and Mo concentrations were well be low levels that would affect Cu metabolism. Similar quantities of the Al-WTR applied to past ures herein have prev iously been shown to reduce environmental P contamination to water s ources. Results from the present experiment show that these Al-WTR applications had little e ffect on animal status of P or any other mineral analyzed. Likewise, Al-WTR had minimal effect on forage mineral concentrations. Lack of AlWTR effects on cattle mineral status and production was likely due to low bioavailability of Al from Al-WTR. Therefore, Al-WTR is one eff ective method of reducing P contamination that does not adversely affect forage or cattle mineral concentrations.
9 CHAPTER ONE INTRODUCTION Waste product management has become a majo r concern in recent ye ars. The amount of waste produced by the worlds population far exceed s the places where it can be disposed of. Each industry has its own set of waste manageme nt problems, and the livestock industry is no different. In the United States alone, the livesto ck industry produces 500 million tons of manure each year (Lorentzen, 2004). Animal manure can be disposed of in several ways, but land application is the most prevalent method of disposal and has benefi cial effects. Manure application to the land improves nutrient uptak e because the manure act s as a fertilizer. However, excessive land application of manur e can have negative environmental impacts, owing to excessive phosphorus (P) buildup in the soil. Too often, manure is over applied because of the large amounts of manure produced and the need to dispose of it. Repeated longterm manure application to the la nd leads to accumulation of P in soils (Novak and Watts, 2004). Once the manure and P have saturated the soils P adsorptive capacity, additional P is subject to being washed away by heavy rains into lakes and streams, or leached downward into the groundwater system. This P lost as leaching and runoff can lead to eutrophication, causing the overgrowth of algae, and decrea sing the survival of aquatic plants and animals (Novak and Watts, 2004). In addition, many coas tal soils used in agriculture have been over fertilized, and much of the soil used by large industrial ag ricultural companies ha s reached its maximum capacity for P adsorption (Novak and Watts, 2004). The drinking-water treatment industry has wa ste management issues as well. The major waste products of this industry are aluminum-water treatment residuals (Al-WTR). The Al-WTR are the solid sediments that resu lt after water is coagulated, le aving behind amorphous Al oxides (Dayton and Basta, 2001). Usually these Al-WTR are placed in landfills for disposal. The Al-
10 WTR usually contains 5 to 8% total aluminum (Al). Because Al is highly reactive and chemically binds P, the application on manure containing soils could be one solution for P pollution of water systems by increasing soil P retention capabilities (Penn and Sims, 2002). Prior research from Florida has shown that ame nding soils with Al-WTR increases soil retention and reduces leaching of P (OConnor et al., 2002). Applying Al-WTR to soils high in P could give the livestock industry another weapon for re ducing water pollution as well as enhancing the perception that the industry is wo rking towards solving the proble m. Fortunately, large quantities of Al-WTR are available from holding ponds associ ated with drinking wate r treatment facilities in some areas. Potential drawbacks to the use of WTR to address both the landfill overflow and P eutrophication, however, exist. The WTR may c ontain sufficient Al to constitute enhanced ecological risk for grazing animals, wildli fe, surrounding floriculture, and water systems (USEPA, 2003). Grazing animals can consume up to 10 to 15% of total dry matter as soil and high dietary Al has been shown to influence the mineral status of the animals, including that of Fe, P, and Mg (Field and Purves, 1964; Heal y, 1967; 1968). The objective of this study was to evaluate the effects of moderate ly high Al-WTR application rate on the performance and mineral status of grazing cattle and on the forage minera l content of pasture grass. The hypothesis was that, even at moderately high a pplication rates, Al in the form of Al-WTR is of only limited availability to cattle, and does not negatively impact forage mineral concentrations.
11 CHAPTER 2 LITERATURE REVIEW The History of Phosphorus The significance of phosphorus (P) in the body and diet has been know n since the 1700s. Even earlier, the disease rickets was common, but not yet associated with P until the 1800s. The essential nature of P in bone developmen t was known in 1769, when bone ash was analyzed, and P was found to be one of the main components of bone material. Phosphorus deficiencies in humans were observed and de scribed as early as 1785 (McDowell, 2003). By 1803, lime phosphate was being fed to children with rickets. The interest in P moved to advances in bone composition, which eventually led to other discov eries of the essentiali ties of P and calcium (Ca). In the early 1900s, Van Niekerk (1978) used P supplementation studies to reveal the cause of bovine botulism and aphosphorosis. He showed that both conditions were the result of a severe P deficiency. Signs included subnormal growth and reproduction and a depraved appetite or pica as illustrated by bone chewin g in cattle. Other countries (Argentina, Brazil, and Senegal) also reported deat h from botulism as a result of bone chewing at different times (Dobereiner et al., 2000). Further, in Piaui, Brazil, an estimated 2 to 3% of approximately 100,000 cattle were dying annually of botulism. Bo tulism, rabies and plant poisoning are the three most important causes of adult cattle mort alities in Brazil today (Dobereiner et al., 2000). In the Gulf Coast area of Texas, Schmidt (1926) reported the prevention of a fatal P deficiency disease of cattle, referred to as creeps, by bone meal and salt supplementation. Becker et al. (1933) classified the disease stiffs or sween ey in Florida and showed it to be caused by a deficiency of P.
12 More recently, a feed table publication in Latin America showed that 73% of all forages evaluated were P deficient (McDowell and Ar thington, 2005). Even today, low P diets and diseases associated with them are problema tic in most tropical regions of the world. Phosphorus Metabolism and Requirements Phosphorus does not occur freely in nature because it is too reactive. Therefore, all of the naturally-occurring P compounds are in bound forms, usually as phosphates. On the earths surface, phosphates always occur in the form of orthophosphates (McDowell, 2003) Even in its bound form, P is the 2nd most abundant mineral element found in the animal body, and 80 to 85% is in bones and teeth (McDowell, 2003). The an imal body could not func tion without P. It controls and is necessary for a wide array of functions in the animals body, including reactions that drive glycolysis and oxida tion of carbohydrates, intestinal ab sorption, lipid transport, and renal excretion (Georgievskii et al., 1981). Phosphorus is also a required part of the nucleic acid molecules, RNA and DNA. In fact, P and the ra te of phosphorylation of the transcription factors affects the rate of nucleic acid transcription and translation, whic h, in turn, affects the rate of protein production (Berner, 1997). Phosphorus plays an importan t role in blood and body fluid buffer systems (Miller, 1985), and is necessary for normal muscle tissue synthesis and milk secretion (McDowell, 2003). It is even further involved in appetite control, a nd in the efficiency of feed utilization, an importa nt facet of animal production (Ternouth and Sevilla, 1990; Underwood and Suttle, 1999). Although P deficiencies are documented in hi story, P problems are easily preventable. Phosphorus is present in all common feedstuffs. A dding seeds that are typical ly higher in P, than are roughages, and seed by-products such as wheat bran and oil meals, can ensure adequate P intake. Feeds containing milk and bone are also high in both P and Ca (McDowell, 2003).
13 Ruminants may have less of a chance of P de ficiency under normal conditions considering that they secrete P naturally in their saliva. Tomas and Somers (1974) suggested, after looking at studies by Australian workers, that salivary glan ds also can play an important role in P homeostasis. They do this by controlling the am ount of P in the gut. Sheep studies provided evidence for this function by ligation of both pa rotid salivary ducts, a procedure that led to a small increase in urinary P excretion and a pr oportional reduction in fecal P excretion (Tomas and Somers, 1974). Therefore, ru minants have a higher renal thre shold for P excretion than do monogastric species, and this can be an a dvantage in P deficient situations. The absorption of Ca and P occurs throughout most of the intestinal tract with the duodenum and jejunum being the most active absorptive sites (McD owell, 2003). This absorption is influenced by many factors includin g: source of P, intestinal pH, animal age, intestinal parasitism and dietary intakes of several other minerals including Ca, Fe, Al, Mn, K, and Mg (MacRae, 1993; McDowell and Arthington, 2005). Large intakes of Fe, Al, and Mg can interfere with the absorption of P by forming insoluble phosphates, chan ging the requirements for the animal entirely (McDowell, 2003). Requirements for P also vary depending on a variety of factors in cluding: age, sex, activity, bioavailability of P, pr otein and energy in the feed, stre ss, interactions between feed ingredients and nutrients, digest ive anatomy, and reproductive stat us of the animal (McDowell, 2003). Therefore, any number of factors can easily affect the absorption of P and the P requirement for the animal. Ruminant animals ha ve a lower requirement for P than monogastrics (NRC, 1985) because ruminants, unlike monogastrics, are able to use phytin P from plants. Only about 1/3 of P in most plants in the form of phytate is actually available for use by nonruminants and, for proper absorption, P must be in the av ailable form (McDowell, 2003). Incomplete
14 uptake by plants can be linked to a variety of fact ors as well. An unavailable chemical form of P in the plant, physical barriers in the plant wall, or an tagonistic substances such as oxalic acid and phytic acid which can bind P, Ca, Fe, Mn, and Zn can all affect the uptake in the plant, thereby affecting the animals food supply (McDow ell, 2003; McDowell and Arthington, 2005). Phosphorus and Ca work together in the body, so their requirements are also linked. A dietary Ca: P ratio between 1:1 a nd 2:1 is assumed to be ideal fo r growth and bone formation as this is approximately the ratio of the two elements in bone. A close ratio is even more critical if P intake is marginal or inadequate (McDowell, 2003). Many factors influence Ca and P absorption, utilization, and metabolism, including adequate levels of one another. The status of Vitamin D is also important to maintain a desirable Ca: P ra tio (McDowell, 2003). In a study of nine Ca:P ratios ranging from 0.41:1 to 14.3:1 tested by Wise et al. (1963), dietar y ratios below 1:1 and over 7:1 caused a decrease in both growth and feed efficiency in animals. Requirements can also be studied on the basi s of P alone. The minimum P requirements recommended by the NRC (2005) may be too high for grazing beef cattle. In a Utah study, no difference in average weight gain s (0.45 kg/day), feed efficiency, or appetite were observed in Hereford heifers fed for 2 years a diet cont aining 0.14% P (66% of N RC recommendation) and comparable heifers receiving the same diet supplemented with monosodium phosphate to provide a total of 0.36% P (Call et al., 1978). W illiams et al. (1991) compared two levels of dietary P (0.12, 0.20%) on various chemical, physic al and mechanical properties of bone in growing beef heifers. In re lation to the requirement, 0.12% P was inadequate as heifers receiving 0.20% P had stronger bone properties and improved overa ll performance. Since there are so many factors influencing the P requirement s for the body, it is difficult to place a normal
15 level on any given species without first looking at the different factor s and interrelationships involved with P. Phosphorus Deficiencies Even with a high renal threshold and available P in common feedst uffs, lack of P is still the most prevalent mineral element deficiency for grazing animals worldwide (McDowell and Arthington, 2005). Some deficienci es can occur from antagonists al one. Certain elements found in low pH tropical soils, such as Fe and Al, can hinder P absorption in the animal. When dietary P becomes low or unavailable, an early physiological response is a decline in inorganic plasma P. Normal plasma P levels in ruminants ar e usually between 4.5 and 6 mg/100 ml. (McDowell and Arthington, 2005) However, when the plasma levels fall, anorexic conditions occur that decrease feed efficiency and slow energy meta bolism in ruminants, such that growth and production levels decline. A significant decline in mineral P concentrations also reduces the ability of animals to properly digest fiber, protein, and carry out nor mal metabolic functions (McDowell, 2003). Deficiencies of P in grazing ruminants have be en reported in 46 tropica l countries in Latin America, Southeast Asia, and Africa. The soil and forages in these livestock-grazing areas of tropical countries can be very low in P (McD owell, 2003). For example, younger grasses may contain 0.3% P, but mature forages may cont ain 0.15% P or less (McDowell, 2003; McDowell and Arthington, 2005). Williams et al. (1990) us ed a noninvasive dual photon absorptiometry technique to show that dietary levels of 0.12 to 0.13 % P lead to bone demineralization in Angus heifers. A heifer fed mature forages with poor mineral supplementation could easily fall below the 0.12% P requirement. When P is deficient, bones can bend and fracture even during normal activities, causing lameness or death (McDowell, 2003)
16 The most devastating economic result of P defi ciency is reproductive failure. Failure to reproduce is associated with loss of body wei ght and body condition, which are the result of decreased intake of feed. The decreased intake of feed could be caused by decreased appetite, impaired locomotion, or both. More research is needed to establish whether reduced reproduction is caused by lack of P or if it is mediated through decr eased body condition instead (Dunn and Moss, 1992). Animals deficient in P have been known to go two to three years without calving, a huge economic loss for the cattle industr y (McDowell, 2003). Phosphorus Impact on the Land There is increasing public demand to reduce P transport to water bodies at risk of eutrophication from agricultural Pinputs. One major agricultural input is the land application of animal manure (Agyin-Birikorang et al., 2007). Although there are rules and regulations in place to reduce the amount of manure spread on la nd each year, many operations go unchecked, causing major environmental concerns. The manure does positively affect the nutrient quality of the soil in the long run, acting as a fertilizer, but the majority of P applied to the land as manure often is converted to insoluble forms in the surface horizon of the soil. The accumulated P is subject to erosion or runoff following heavy rains a nd transport to surface wa ter. Regulations on manure application rates are placed in order to avoid the P pollution of surface waters (Dayton and Basta, 2001; OConnor et al., 2002; Dayton et al., 2003 ). According to recent environmental research, the sheer mass of manure generated by la rge animal facilities po ses risk to ground and surface water ( Lorentzen, 2004) The EPA suggests that farming creates 455 million metric tons of manure each year (Lorentzen, 2004). Many states have passed more st rict rules on the land application of animal manure. In Maryland, for example, all P applications must abide by the Water Quality Act of 1988, which dictates soil testing of P and de termines to the degr ee of soil saturation w ith P, and if manure
17 application can be permitted. In Virginia, food animal practices ar e closely scrutinized, particularly the poultry industry. In Delaware, manure can usually be applied onc e every three years to comply with soil P limitations (Penn a nd Simms, 2002) However, in California, lax enforcement of the law has led to an overabundan ce in the pollutant count in several bodies of water with both P and N. Leaching and runoff fr om manure enriched soils is thought to be the primary cause. The reality is that this type of manure utilization is a matter of convenience, availability, and profitab ility rather than providing the optimal nutrients for the flora or concern for the ecosystem (Farm Press, 2004). Both N and P are constituents within animal waste products, and are harmful pollutant s, yet federal, state, and county standards differ in the applicable uses and concentrations of manure fo r land, resulting in conf usion as to how manure should be properly applied. The National Resour ce Conservation Service (NRCS) has attempted to control over-fertiliz ation by implementing nutrient management plans. In most cases, though, the manure application rates for nutrient manage ment plans are based on the N needs of the crops. When the amount of manure applied to cropland is based on crop N needs and not on the amount of P needed, over-applica tion of P may occur. (Shirmohammadi and Ritter, 2000). Calcium Together, Ca and P are the most abundant mine rals in the animals body. Combined, these two minerals make up 70% of the minerals found in the body (McDowell, 2003). Calcium, by itself, is the most abundant mineral element in th e animal (1-2%), and 99% of Ca occurs in bone and teeth. The remainder, constituting the physiol ogically active pool of free Ca, is found in the extracellular fluid and within cells (McDowell, 2003). Calcium is important to many of the processes necessary for life to f unction properly. For example, Ca is essential for normal blood clotting. The Ca ion must be present for prothrom bin to form thrombin, which then reacts with fibrinogen to form the blood clot, fibrin (McDow ell, 2000). Calcium also plays a role as a
18 cofactor in many enzymatic reactions, acting as an activator or stabilizer of enzymes (Peo, 1976) and is necessary for the secretion of a num ber of hormones and hormone-releasing factors (Arnaud and Sanchez, 1996). Dietary Ca can act as a defense mechanism by decreasing gastrointestinal lead (Pb) ab sorption and thereby reducing the risk for Pb poisoning in the body (Ballew and Bowman, 2001) or as a contributor to the regulation of the cell cycle (McDowell, 2003). Regulation of Ca and P occurs as a result of the hormone 1,25-di hydroxycholecalciferol, parathyroid hormone, and calcitoni n. Normal levels of all de pend on factors such as bodily excretion, bone deposition, resorp tion, and intestinal ab sorption (McDowell, 2003). If Ca and P needs are not met through the diet, tetany can occu r as the animal draws Ca and P from the bone in order to maintain its normal blood concen trations (McDowell and Arthington, 2005). However, animals will also absorb Ca from thei r gut according to need, and they can alter the efficiency of absorption to meet a change in requirement. The ARC (1980) documented that young sheep have a high Ca requirement and absorb Ca at a higher rate than do mature animals with a low requirement. In contrast to that of Ca the percentage of P absorbed is not so closely tied to the needs of the animal (ARC, 1980). Theref ore, when dietary Ca is relatively low, most of the Ca absorption is by activ e transport (Goodrich et al., 1985). Serum Ca concentration also varies little in spite of larg e changes in dietary Ca because of the bodys internal method of endocrine regulation. Blood cells are almost entir ely devoid of Ca, but h ealthy plasma contains from 9 to 12 mg per 100 ml in most species, and in all species, feces are the primary path for Ca excretion (McDowell, 2003). Calcium is generally abundant in most fo rages (McDowell, 2003). Non-legume roughages such as grass hay and mature range forages have average Ca concen tration (0.31-0.36%), and
19 legume forages such as alfalfa and clover hay contain 1.2 to 1.7% Ca (NRC, 2005). When there is insufficient dietary intake of Ca and the needs of Ca are high, as in a lactating dairy cow, a Ca deficiency called milk fever can occur. Milk fever in dairy cows is caused by a temporary imbalance between Ca availability and high Ca demand following the onset of lactation (Oetzel, 1996). Despite much research, milk fever inciden ce has remained steady in the United States at 8 to 9% (Goff, 1989). Magnesium Magnesium is the 2nd most plentiful cation of intracellula r fluids and is widely distributed among plant and animal tissues with some 70% of total body Mg present in bones (McDowell and Arthington, 2005). As a major macromineral, Mg has a very important role as an essential ion in many fundamental reactions in intermediary me tabolism and also as an activator of enzymes. In fact, Mg is vitally involved in the metabolism of carbohydrates and lipids as a catalyst of a wide array of enzymes which requ ire this element for optimal activity. Magnesium is involved in at least 300 enzymatic steps in intermediary metabolism (Shils, 1996). It is also involved in certain steps of protein synthesis through its acti on on ribosomal aggregation, its roles in binding messenger RNA to 70S ribosomes and in the synthesi s and degradation of DNA. Furthermore, Mg plays an important ro le in neuromuscular tr ansmission and activity (McDowell and Arthington, 2005). Many dietary factors influence Mg absorption as well as Mg requirement s, and include: K, Ca, P, Al, Fe, Na, protein, fat, organic aci ds, carbohydrate type, i onophores, Mg status, and frequency of feeding (Fontenot et al., 1989). In mature ruminants, the reticulorumen is the principal site of Mg absorption (Thomas and Potter, 1976). As a regulation mechanism, the proportion of Mg absorbed declines with incr easing dietary levels (H eaton, 1960), and the Mg status of the animal alters Mg absorption (McA leese et al., 1961). Minima l requirements of Mg
20 for growth of grazing livestock can generally be met by pastures and diets containing 0.10 to 0.15% (McDowell, 2003). Henry and Benz (1995) repor ted that apparent availability of Mg in fresh grasses or grass hays varied greatly from -4% to +66%. Seemingly, most practical diets contain adequate Mg to promote op timal performance (McDowell, 2003). The serious metabolic disorder in cows, know n as lactation tetany or grass tetany, was shown to be associated with subnormal serum Mg values (McDowell, 2003). For diagnosis, the ranges in serum or plasma Mg level (mg/100 ml) for cattle and sheep are as follows: normal values, 1.8-3.2; slight hypomagnesemia 1.2-1.8; and severe hypomagnesemia 1.2 or less (NCMN, 1973). Hypomagnesemia te tany in sheep is almost exclus ively a disease of the first 8 weeks of lactation with ewes nur sing twins being the most susceptib le. The incidence is highest 1-4 weeks after lambing (Herd, 1966). In Austra lia, a high incidence of hypomagnesemia tetany in breeding ewes has been corr elated with periods of rapid winter growth of pastures (Underwood and Suttle, 1999). Fertiliz ation can also be a factor in the incidence of grass tetany. In general, high N fertilization results in lower serum Mg concentration a nd a higher incidence of grass tetany (Kemp, 1983). Grass tetany is endemi c in some countries, affecting only a small proportion of cattle (1 to 2%). However, individu al herds may report incidence of tetany as high as 20% (McDowell and Arthington, 2005). Th e incidence of nonclinical hypomagnesemia, although not usually characterized by death, is far greater than grass tetany, and the economic consequences of lowered production can be substantial. Aluminum Aluminum is the third most abundant element in the earths crust, followed by silicon and oxygen. It is also the most common metal f ound in the earths crust (OConnor et al., 2002). Aluminum and P are similar, not in their essentia lity per se, but in their reactive nature. Given that Al is highly reactive, it doe s not normally appear in its el emental form, and instead it is
21 bound to other elements or compounds like P in nature (McDowell, 2003). Considered by some to be a trace element, Al is not actually need ed by the body and is considered to be a toxic element in most cases. It is generally not c onsidered to be an essential element and has no critical levels but may possibly be required in female rodents (McDowell, 2003). Yet, Al may still perform some positive functions when utiliz ed as a cofactor in some processes. For example, Al promotes the reaction between cytochrome c and succinic dehydrogenase (Horecker et al., 1939) and has been shown to be a cofactor for the activation of gu anine nucleotide-binding regulating protein by fluoride for the stimulation of anenylate cyclase activity (Sternweis and Gilman, 1982). However, it is not at this time known to be invol ved in these reactions in the human body. Most of the time, Al causes problems for th e body. Aluminum can accumulate in the body whenever uptake exceeds the disposal of this metal via urinary biliary excretion (Greger and Sutherland, 1997). It would appear that the major pathway for th e elimination of any absorbed or systematically administered Al is the kidneys (Alfrey, 1986). Toxic accumulations most often result from large oral intakes, contaminated pa renteral solutions, or in individuals with renal insufficiency. Aluminum toxicity has been clearl y demonstrated in patients with renal failure (Flaten et al., 1996). The mechanisms by which Al exerts its toxicity are not well understood, although Al has been shown to interfere with a variety of biological and enzymatic processes (Alfrey, 1986). Garrel et al. (2000) suggested that the deleterious eff ect of Al may be to decrease the level of antioxidant enzymes through an interaction w ith DNA, which would then alter the ability of cells to be effectively protected from oxidative stress. Regarding its sk eletal toxicity, Al has been shown to be deposited in the mitochondria of osteoblasts and to inhibit formation of bone
22 phosphates as well (Lieberherr et al., 1982). Additionally, Al toxic ity can alter the regulation of calbindin, a vitamin D-dependent protein (Cox and Dunn, 2001). Al ong with other toxic effects, research has shown that excess Al can form complexes with P and other minerals affecting their utilization prior to absorption, th ereby affecting mineral metabolism post absorption (Valdivia et al., 1982). Other toxic effects of Al include abil ity to inhibit cell extension and division and interference with plant mineral nutrition (Matsumoto et al., 1977). Because Al binds to DNA in plant cell nuclei, it can limit template activit y, which would further explain much of the deleterious effects of Al on plant metabolism (Matsumoto et al., 1977). In humans, Al has three potential toxic effects: (1) a local e ffect in the gastrointestinal tract, (2) the potential to cause pulmonary damage if inhaled, and (3 ) a capacity to exert systemic toxicity if absorbed or parenter ally administered. The latter effect can also be broken down further into neural and skeletal toxicities. Aluminum can bind to brain calmodulin and change calbindins configuration and its interaction with other pr oteins (Siegel and Hang, 1983). Regarding its skeletal toxici ty, Al has been shown to deposit between mineralized and unmineralized bone at the calci fication front preven ting tetracycline labeling. This would suggest that it might locally pr event further mineralization of osteoid (Malony et al., 1982). Further, Al has been shown to inhibit bone phosphates (Lieberherr et al., 1982). Aluminum, especially in association with ci trate, has been shown to inhibit crystal growth, which might also interfere with mineralization. So me suggest that inhibition of glycolysis and phosphorylation is the most toxic reaction caused by Al (Sorensen et al., 1974). Aluminum has also been shown to displace Mg from ATP with the resulting stabili zation of ATP, thereby preventing phosphate transfer by Na+, K+ -ATPase (Harrison et al., 1972; Lai et al., 1980). All phosphate-transferring systems involving ATP and Mg may be biologic al targets for Al (Sorensen et al., 1974).
23 The maximum tolerable levels of Al for liv estock include: cattle and sheep, 1000 ppm; swine, poultry, and sheep, 200 ppm (NRC, 2005). Soil Al concentrations can range from 1-30% but are typically 0.5-10% by weight (OConnor et al., 2002). Since grazing animals can consume up to 10% of their daily intake as soil, Al toxicity is a major concern for many causative factors leading to decreasing animal health and profitabilit y. Ingestion of soil containing Al has been implicated as a causative factor of gra ss tetany (Dennis, 1971; Allen and Robinson, 1980). With the increase of acid rain from pollutants in the air, Al has been rendered more soluble in surface waters and has a greate r potential for causing plant toxicity as well (Johnson et al., 1984). Interactions Between Al and P Aluminum may interact with essential elemen ts, namely P, Ca, Mg, and fluoride (F), and adversely affect their metabolism in animals (Alle n, 1984). With the unstable, reactive nature of Al and P, as well as their abundance in most soils, interactions between these minerals may increase dietary requirements for P and cause toxic and/ or deficient impli cations with Al and P, respectively. It is not uncommon to find high amounts of Al complexes in tropical sandy soils that bind soil P and make it unavailable for plant uptake (M cDowell, 2003). In some cases, soil Al may be in a less available chemical form than that of the inorganic salts and t hus have less effect on P availability (Robinson et al., 1984). Nevertheless, land applicati on of highly soluble Al salts, e.g. Al chloride (AlCl3) and other Al compounds are used to combat P runoff and leaching. Many researchers suggest that excess dietary Al interferes with P utilization by forming unavailable complexes in the gastrointestinal tract (Jones, 1938; Storer and Nelson, 1968). For example, Rosa et al. (1982) repor ted that increases in dietary P in sheep increased feed intake while it was decreased by adding Al and Fe. Increased dietary levels of Fe and Al in sheep diets
24 resulted in a decrease in ADG from 157 to 97 g/d in high Fe diets and from 159 to 95 g/d in high Al diets. When additional P was added to di ets containing high Fe and Al, average daily gain (ADG) losses were minimized. The rationale for this response was that the diet being fed was borderline to deficient in P eith er at 0.17% to 0.23% (NRC, 1985). Additionally, plasma P levels increased with high Fe and decrea sed with high Al diets (Rosa et al., 1982). What seems to be happening in the body is that an insoluble complex of Al and P is formed in the digestive system of the animal, binding P and making it unavailable to the animal. This has been seen in sheep fed high levels of Al, and signs of P deficiency resu lted (Valdivia et al., 1982 ). Rosa et al. (1982) concluded that excessive bioavaila ble dietary Al increases P requi rements. Animals are not the only ones to suffer either. Crop yields could be negatively impacted if too much P is bound to Al or if increases in heavy metal contents are realized within th e soil as well (Novak and Watts, 2004). Water Treatment Residuals Water treatment residuals (WTR) are by-product s of water purificati on procedures. They are rich in metals like Al and Fe, though the ex act composition can vary due to the process in which they are made and the age and dryness of the WTR (Dayton et al ., 2003; Ippolito et al., 2003). Several authors (Elliott et al., 2002; Basta et al., 2003; Lind, 2003; Novak and Watts, 2004) have suggested that WTRs can serve as low-cost soil amendments to reduce environmental impacts of various oxyanions, not ably P and As. However, these drinking-water treatment plant facilities use different water sources and different ch emicals, and the WTR produced can have widely different elemental compositions and P so rption capacities (Makris and OConnor, 2007) During the water treatment proce ss, a chemical, called a coagulate, is added to the water. This causes a reaction and forms a flocculent prec ipitate, which coats small particles, such as
25 clays making them more likely to be removed by se dimentation or filtrati on. Aluminum, iron, or calcium sulfate coagulates may be added to unfilte red water, which is then circulated with vigor to uniformly disperse the product. The product th en reacts readily with alkaline products within the water and produces a hydroxide solid, which has entrapped impurities (Dayton and Basta, 2001; Brady and Weil, 2002; Ippolito et al., 2003; Water Resources, 2005). In the basic pH environment of a typical drinking-w ater treatment facility, Fe or Al salts added in the raw water hydrolyze to form Fe or Al hydroxides. This pr ocess of coagulation a nd sedimentation usually precedes filtration in a water treatment plant, an d serves to reduce turbidity and increase the efficacy of bacterial removal by filtration (D ayton and Basta, 2001; Brady and Weil, 2002; Ippolito et al., 2003; Water Resources, 2005). Poorly P-sorbing soils are abundant in sout heastern United States These sandy (coarsetextured) soils are characterized by low P-sorb ing capacities, and are often accompanied by high water tables. This combination of characteristics makes such soils vulnerable to P losses and negative water quality impacts (Makris and OC onnor, 2007). Highly reacti ve Al could be one solution to managing the P pollution but with possible harmful side -effects. There is a better answer. More than 2 million Mg of Al-WTR are generated from dri nking-water treatment facilities in the U.S. every day (Prakash and Sengupta, 2003), making Al-WTR a suitable substitute for highly reactive Al compounds to reduce the P pollution problem. These Al-WTR can be disposed: a) directly to the receiving st ream; b) to sanitary sewers; c) to a landfill, assuming that the residual contai ns no free-draining water and does not have toxic characteristics as defined by the Toxicity Characteristic Le aching Procedure (TCLP) test; and d) by land application (Chwirka et al., 2001) Al-WTR are specifically ex empt from the 40 CFR Part 503 land disposal regulation for biosolids (USEPA 1996) Thus, Al-WTR can be land-applied
26 without having to meet metal (including As) lim itations of the Part 503 regulation, which will allow for easier, less-expensive application Also the disposal cost of non-hazardous Al-WTR is low; estimated at < $50/Mg (Meng et al., 2001). Therefore, land applicaton of Al-WTR can be a cost-effective treatment for effec tively sorbing excess levels of labile P (or other oxyanions, e.g., As, Mo, Se) in soils. The high amorphous Al or Fe content of the Al-WTR would be expected to increase a soils P-sorption cap acity (Elliott et al., 1990). The physical and chemical characteristics of Al-WTR are quite similar to top soils (Haustein et al., 2000). Elliott and Dempsey (1991) tested Fe and Al-WTR and showed that mean total metal concentrations of heavy meta ls Cr, Ni, Pb, and Zn were within the common range for soils, implying that total metal soil concentrations will remain largely unaffected by Al-WTR application at typical lo ading rates. Work by OConnor et al. (2002) showed that a CaWTR was much less effective in sorbing P th an a Feand an Al-W TR. X-ray diffraction analysis of Feand Al-WTR suggests that am orphous Al or Fe hydroxide s dominate the Al-and the Fe-WTR, respectively, with no apparent crys talline components. Oxalate-extractable Al values are typically 80-90% of total Al of Al -WTR, which supports the amorphous model of AlWTR (Makris and OConnor, 2007), and allows for the uptake of P. Gallimore et al. (1999) concluded that the amorphous, rather than the to tal Al content of Al-WTR determines their effectiveness in reducing runo ff-P (Makris and OConnor, 2007). The Pros and Cons of Al-WTR High dietary Al has been shown to influence st atus of Fe, Zn, P, Mg, and bone ash in sheep (Rosa et al., 1982). Research at th e University of Florida conclude d that increases in dietary Al levels reduced feed intake, gains and P plasma concentrations in sheep (Rosa et al., 1982). The Al given to these animals was in the form of AlCl3. The impact of additional Al was not positive for animal gains as ADG was 105 and 148 g/d for t hose consuming a high Al or low Al diet,
27 respectively. When additiona l dietary P was given, ADG increased, but not to the level in animals not consuming any Al (Rosa at al., 1982). This indicates the prob lem with using Al in such a reactive form. In addition, other mineral pl asma concentrations were also impaired with increased dietary Al. Magnesium content was depressed in the kidneys and bone of those animals receiving high dietary Al (Rosa et al., 1982). Similar results have also been documented at Rutgers University in avian species. Young chicks and mallard ducks fed high Al diets (as AlCl3) had a high incidence of P binding, lowered P serum levels, depressed growth, lowered tibia weights and lower bone minera lization (Capdevielle et al., 1998). Al-WTR may seem like the end-all solution to P polluti on, but some researchers are skeptical. Also, laboratory and greenhouse data suggest that application rates as high as 25 T/A are required to control P sol ubility in highly P-impacted soils (OConnor et al., 2002). Regardless, the use of Al-WTR and metal-bindi ng by-products could be one solution to the accumulation of P on the top layer of soil, which leads to nonpoint pollution during heavy rains (Penn and Sims, 2002). Research from Florida ha s shown that amending soils with Al-WTR can increase soil P retention and dramatically redu ce its leaching potential (Elliott et al., 2002; OConnor et al., 2002). Al-WTR ar e particularly effective in c ontrolling soluble P in acid sandy Florida soils of limited P sorption capacity (Ellio tt et al., 2002). In particular, Al-WTR would benefit sandy soils low in organic material. Sa ndy soils tend to provi de little P retention capabilities and P loss is likely. Soils that are saturated with P may also benefit from Al-WTR application. Phosphorus-saturated soils are unabl e to hold additional P, which can result in P ground water contamination (Penn and Sims, 2002). Other research shows that added Al in the form of Al-WTR may help depr ess P losses by increasing soil P retention capabi lities (OConnor et al., 2002; Penn and Sims, 2002). Phosphorus adsorption capacity was increased by 20 times
28 with the use of Al-WTR when compared to high Al clay (Haustein et al ., 2000). Gallimore et al. (1999) applied an Al-WTR to poultry litter-am ended soils, and reduced soluble P in surface runoff. Haustein et al. (2000) documented decr easing P concentrations in runoff from fields excessively high in soil test P following amendm ent with an Al-WTR (rates up to 18 Mg/ha). Moreover, Peters and Basta (1996) significantly re duced (~50% of the initi al values) soil testextractable P concentrations of an acidic and calcareous soil inc ubated with high loading rates of two different Al-WTR (~60 and 200 Mg/ha). Codli ng et al., 2000 incorporated either Feor Albased WTR into poultry litter-amended soils a nd significantly reduced P-leaching. Similarly, surface-applied Al-WTR had little effect on P av ailability to wheat in a greenhouse study, but incorporation into the entire soil significantly decr eased P availability (Cox et al., 1997). Elliott et al. (2002) showed that either Feor Al-WTR reduced P leac hing in a low P-sorbing FL sand amended with dewatered biosolids and tr iple superphosphate (TSP) fertilizer. More studies are now available that compare the differences in AlCl3 with Al-WTR. In a recent study at the University of Florida, lamb ADG, BW, and intakes were unaffected by dietary Al-WTR (P>0.05) when compared to the control. However, lambs fed 2,000 ppm Al from AlCl3 had reduced growth and lower ADG (P<0.05) than other treatments (VanAlstyne et al., 2005). The Al-WTR did not appear to negatively affect performance of growing sheep. The apparent P absorption data strengthens the idea that Al in the form of Al-WTR is less available to the animal than the Al in AlCl3. Additionally, plasma P and tissue mineral levels, with the exception of brain Al, were not altered with the admini stration of Al from Al-WTR. Under these experimental conditions, dietary administration of Al from Al-W TR did not cause physiological tissue damage. Overall, it was demonstrated that Al from Al-WTR does not negatively impact a
29 growing lambs health or performance and could be administered at leve ls as high as 8,000 ppm Al without causing detrimental e ffects (VanAlstyne et al., 2005). One question asked by many environmentalists is whether the fixed P will ever dissociate from the Al-WTR. In the past, insufficient data were available on the lo ng-term stability of P retained by Al-WTR, or soils ame nded with Al-WTR, or metal salts, and the long-term stability of immobilized P was a major concern of stat e and federal regulator s (Makris and OConnor, 2007). A 6.5 year field study of Al-WTR effectiv eness in reducing water extractable P in two soils with excessively high soil test P leve ls was conducted (Jacobs and Teppen, 2000, ; AgyinBirikorang et al., 2007; Makris and OConnor, 2007). Soil samples taken each year for up to 6.5 years after an initial Al-WTR application showed sustained reduction (up to 63% initial values) of water-soluble P levels in the Al-WTR-amended plots. Potential Al-WTR particle di ssolution, particularly under ac idic conditions, is a concern with respect to Al-WTR field applications in humid regions. Aluminum-based Al-WTR particle dissolution in soils or aqueous suspensions mi ght not only release si gnificant quantities of potentially toxic Al, but allow previously immobilized P to be released to the environment (Makris and OConnor, 2007). Long-term (80 d) e quilibrations of Al-WTR were conducted in unbuffered 0.01 M KCl solutions (Makris and OC onnor, 2007). Soluble Al concentrations of untreated (no P added) Al-WTR were below th e instruments (ICP-AES) detection limit (0.03 mg Al/L). Overall, the amount of KCl-extractable Al concentrations rele ased from Al-WTR within 80 d was minimal (<0.1% of oxalate-e xtractable Al) (Makri s and OConnor, 2007). Agyin-Birikorang and OConnor (2007) also concl uded in an artificial Al-WTR aging study that WTR application is capable of reducing P concentr ations in P-impacted soils, doing so for a long
30 time, and that within the commonly encountered range of pH values for agricultural soils WTRimmobilized P should be stable.
31 CHAPTER THREE EFFECTS OF ALUMINUM FROM WATER TR EATMENT RESIDUAL APPLICATIONS TO PASTURES ON MINERAL STATUS OF GRAZING CA TTLE AND MINERAL CONCENTRATIONS OF FORAGES Introduction There is an increasing public demand to re duce the amount of phosphor us (P) transported to water bodies due to the risk of eutrophication, mainly from ag ricultural P-inputs, including the land application of animal manure. Extensive efforts have been focused on finding ways to reduce soluble P in manure-impacted soils. Alumin um (Al) binds to P and application of Al could be one potential solution to the problem. However, applica tion of Al to the land can also result in ingestion by livestock and potential ha rm to animals. Under grazing conditions, cattle typically consume 10 to 15% of their DM inta ke as soil (Field and Purves, 1964; Healy, 1967; 1968). However, this work was done with cool season grasses and may not directly apply to tropical grasses. Ingestion of hi ghly available dietary Al (e.g. AlCl3) by cattle and other livestock may result in a P deficiency. Notably, Al toxicity is often observed as a P deficiency (Valdivia et al., 1982). High amounts of bioavail able Al can also impact the status of Fe, Mg, and Zn in animals (Rosa et al., 1982). In sheep, for exampl e, ingestion of soluble dietary Al suppressed voluntary feed intake, feed efficiency, plasma P, animal growth, and gains. However, when additional P was offered, the nega tive effects were less severe. Aluminum water treatment resi duals (Al-WTR) are the by-produc ts of a water purification procedure. They may be one solution to the P problem, in that the Al in the product will bind with P, thus preventing leaching into groundwater. Prior research from Florida has shown that amending soils with Al-WTR increases soil rete ntion and reduces leachi ng of P (OConnor et al., 2002). Unlike AlCl3, the bioavailability of Al in Al-WTR is generally low and thought to be harmless (OConnor et al., 2002).
32 Two experiments were conducted to determine the effects of pastur e application of AlWTR on mineral status (primarily P) and performance of grazi ng cattle. A second objective was to evaluate the effects of the applied Al-WTR on forage mineral concentrations. Materials and Methods Two experiments were carried out in consecu tive years, 2005 and 2006, to study the effects of Al-WTR on cattle mineral stat us and performance and forage mineral concentrations. The second experiment (2006) involved a different group of cattle and additional application of AlWTR at the same location. All animal procedures were conducted within the guidelines of and approved by the University of Florida Institutional Animal Ca re and Use committee (No. E037). Experiment 1 (2005) Yearling Holstein steers (n=36) were utilized in a 148 d experi ment at the Santa Fe Beef Research Unit, a 648 ha operation owned by the Un iversity of Florida, located in Alachua County (north central FL). The experiment began on June 1st and ended October 26th, 2005. The steers weighed 306.7 34.5 kg at d 0. The cattle were not dewormed before the trial, but received a free-choice complete mineral salt prior to the beginning of the trial so that they would not be salt-starved and thus, be accustomed to eating free-choi ce minerals early in the study. Steers were allotted (three/ pasture) to one of tw elve 0.81 ha bahiagrass ( Paspalum notatum ) pastures on d 0 and provided ad libitum water and grazing access. The chemical composition of forages can be found in Appendix A. Soil series that exis t at this location are Millhopper sand, Bonneau fine sand and Gaines ville sand. Experimental pastures were randomly allotted to one of four treatments with three replications per treatment. Half of the twelve pastures received Al-WTR at a rate of 22.8 Mg dry weight/ha from the Bradenton, FL, water treatment plant. Bradenton, FL water treatment pl ant was chosen based on the reactivity of the Al-WTR at this location in previous studies, a nd this rate of Al-WTR is also consistent with
33 previous studies (Makris and OConnor, 2007). The Al-WTR product contained 0.30% Fe, 7.8% Al, 0.11% Ca, 0.024% Mg, 0.30% P, 0.004% Mn, 0.73% S, 0.006% Cu, 0.002% Zn, and approximately 70% solids. The treatments were 1) control-no Al-WTR application with steers receiving commercial free-choice mineral supplem ent but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR. The mineral supplement was provided in covered minera l feeders located in ea ch pasture. Mineral supplement was offered every 28 days in 11.34 kg in crements starting on d 0 and continuing to d148. Pastures were clipped to a height of 0.01 m and Al-WTR was surface applied to the pastures from one to two days prior to grazi ng using a spreader truck. All pastures were fertilized with 190 kg N/ha as ammonium nitrate before Al-WTR application. Weights, blood, and liver biopsies were take n at d 0, d 84, and d 148. Bone biopsies were obtained on d 148. Blood samples (jugular venipunc ture) were collected (10 mL) with a 20 x 1 vacutainer needle (Vacutainer; Becton Dickinson, Franklin La kes, NJ) into evacuated tubes containing sodium heparin. Immediately after co llection, blood was centri fuged for 20 min. at 700 x g, and plasma was then extracted. Plasma was kept on ice at th e collection site, and subsequently transported to the University of Florida for further preparation and analysis. Plasma was frozen at -20 C upon arrival at the laboratory. Stored plasma samples were thawed and deproteinated using 10% trichl oroacetic acid (Miles et al., 2001). Plasma was analyzed for Al, Ca, Cu, Mg, P, and Zn. Liver biopsies were obtained in vivo using the aspiration liver biopsy technique (Miles et al., 2001). Liver samples (0.1-0.8g DM) were placed on filter paper to remove the excess blood, placed in a sterile plastic bag, and sealed. Bags were cooled on ice until transportation to the laboratory where they were frozen at -20 C until time of analys is. Liver samples were thawed,
34 dried, weighed, ashed, and solubilized in HNO3 (Miles et al; 2001). Liver samples were analyzed for Al, Cu, and P. Bone samples were collected us ing an electric drill and trep hine (1.5 cm) as described by Miles et al. (2001). Bone samples were sealed in sterile plastic bags and kept on ice, then frozen until the time of analysis. Bone samples were th awed, washed with saline, cleaned of all soft tissue, dried, and fat extracted with petroleum ether before ashing. Bone samples were then analyzed for Al, Ca, P, and Mg as described in M iles et al. (2001). Forage samples were taken on d 0 and approxima tely every 28 d thereafter for five mo. Two composite forage samples were taken from each 0.8 ha pasture using a transect technique. Subsamples of each composite sample were ta ken from the beginning, middle, and end of the pastures, no closer than 10 m from the fences. The subsamples were cut to a height of 3-5 cm to simulate observed grazing height and were collect ed at different areas of the pasture to more closely mimic what the animals appeared to cons ume. The forage samples were clipped using a stainless steel knife, and placed into clean pa per bags on location. Samples were cut with stainless steel scissors and placed into clean pa per bags on location. Samples were transported to the laboratory where they were dried in an oven at 60 C for 48 hr and subsequently ground, using a Wiley Mill, with a 1-mm stainless steel sieve. Ground samples were stored in air-tight plastic bags until analysis. Samples were prepared and digested according to Miles et al. (2001). Forage samples were analyzed for Al, Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn. Cobalt and Mo were analyzed on samples collected in three of the five months (May, August, and November). Selenium was analyzed for one-third of the samples collected each month. For all samples, Ca, Cu, Fe, K, Mg, Mn, Na, and Zn were determined by atomic absorption spectrophotometry (Perkin-Elmer Model 5000, Perk in-Elmer Corp., Norwalk, CT). To ensure
35 the quality of data, the calibra tion standards were prepared s imultaneously and the standard curves were recalibrated in the middle and at the end of each set of samples analyzed. In addition, to ensure the overall re liability of the analytical methods certified National Bureau of Standards (NBS) reference materials (citrus leaves SRM-1572; bovine liver SRM-1577a) were acquired from the National Institute of Sta ndards and Technology (NIST; Gaithersburg, MD) and included as standards. Colorimetric de termination of P was accomplished using a method described by Harris and Popat (1954). Selenium was determined using fluorometric procedures (Whetter and Ullrey, 1978). Aluminum concentra tions were analyzed by inductively coupled plasma-atomic emissions spectroscopy (ICP-AES) (Perkin-Elmer Plasma 3200, Perkin-Elmer, Wellesley, MA). Cobalt and Mo were determin ed at a private lab (A dvanced Environmental Laboratories, Inc., Gainesville, FL) using ICP-AE S. Data were analyzed for treatment effects using PROC MIXED og SAS (SAS for Windows v9; SAS Inst., Inc. Cary, NC) for a completely randomized design with a 2x2 arrangement of treat ments. A repeated measures statement was included. Post hoc testing was done to determine sampling date effects with the PDIFF statement of SAS. Contrasts (control vs Al-WTR, no P vs. P, and the interaction) were used for mean separation. Significance was declared at P < 0.05. Experiment 2 (2006) Yearling Holstein steers (n=36) were utilized in a second expe riment (145 d) at the same location used for Experiment 1. The experi ment began on May 23rd and ended October 15th, 2006. Steers weighed 169 8.8 kg at d 0. Steers were dewormed with Dectomax (Pfizer Animal Health, Cambridge, MA) and fed mineral salts before the start of the trial. The same treatments used in experiment 1 were examined. An additional 53 Mg dry weight/ha from the Bradenton, FL water treatment plant was applied to th e same pastures that received Al-WTR in 2005. The total 2-year load of WTR was 75.8 Mg dry weight/ha on the
36 pastures. The second application of Al-WTR was applied to the pastures 5 to 19 d prior to initiation of grazing. All pastures were fertilized with 190 kg N/ha as ammonium nitrate before Al-WTR application. Weights, blood, and liver biopsies were take n at d 0, d 70, and d 145. Bone samples were taken on d 145. Forage samples were taken at d 0 and approximately every 28 d thereafter for six mo. Blood, liver, bone, and forage samples we re analyzed for the same minerals, minus Co and Mo, and utilized the same experimental pr ocedures as Experiment 1. All other animal management, sample preparations, and statistical evaluations were the same as those reported for Experiment 1. Results and Discussion There were no interactions between P and Al-WTR during Experiments 1 and 2. Performance Results (Experiment 1) The experimental pastures provided adequate forage throughout the experiment. The steers consumed the free-choice mineral supplemen t throughout the experiment and the average consumption varied from 34 to 55 g/animal/d am ong treatments. Increases in body weight were observed as the experiment progressed for all treatments except in treatment 2, when the body weight decreased from d0 to d84 (Table 3-1). The greatest increases (P<0.05) occurred from d 84 to d 148 in all treatments. Average daily gain s were generally low for all treatments, ranging from 0.17 to 0.23 kg/d, with no treat ment differences (P>0.05). Performance Results (Experiment 2) There were no treatment differences (P>0.05) in BW of the steers, except at experiment termination, where in treatment 2, cattle had lowe r weights (P<0.05) than treatment 3 (Table 32). Average daily gains (ADG) ranged from 0.39 to 0.48 kg/d. The experimental pastures provided
37 Table 3-1. Effect of Aluminum-water treatmen t residuals (Al-WTR) and P supplementation on Experiment 1 Steer Body Weights (kg) 1-3 Day Trt 0 70 145* Mean SD 1 307a 309a 343b 320 20.2 2 312a 307a 340b 320 17.8 3 307a 310a 332b 316 13.7 4 302a 302a 335b 313 19.1 SD 4.14 3.69 4.95 3.40 a,b Means with same letters within rows are not different (P>0.05). 1 Data represent treatment least square means and standard deviations. 2 Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR. 3 Animals received free-choice mineral suppleme nt with the following minerals: Ca, 16-18%; P, 8% (treatments 2 and 4 only); NaCl, 2327%; Mg, 2%; Fe, 1%; Co, 50 mg/kg; Cu, 500 mg/kg; I, 50 mg/kg; Mn, 2000 mg/ kg; Se, 26 mg/kg; and Zn, 4000 mg/kg. 4 Average mineral consumption for each treatment was as follows: 1) 48 g/animal/d; 2) 67 g/animal/d; 3) 53 g/anim al/d; 4) 62 g/animal/d.
38 adequate forage and the steers consumed fr ee-choice mineral supplement in amounts varying from 48 to 67 g/animal/d throughout the experiment As the experiment continued, increases in body weight (P<0.05) were observed for all treatments. Performance Discussion In general, differences in animal performa nce among treatments were limited throughout the experiment in both years. The study show ed few losses in weight, which seems to be attributed to the proper amounts of dietary P supplied, as well as ot her nutrients. In experiment 2, steers receiving the complete mineral supple ment, including P, had lower BW gains than steers grazing Al-WTR pastures and receiving a P-free mineral supplement. Cattle from experiment 2 had higher ADG values rangi ng from 0.39 to 0.48 kg/d, compared with ADG values for steers in experiment 1 ranging from 0.17 to 0.23 kg/d. Possible explanations for the higher gains in experiment 2 incl ude lower starting we ights, deworming before the experiment, and higher daily consumption of supplemental minera ls. In both experiments, application of AlWTR to pastures of grazing ruminants to cont rol environmental P was not detrimental to the animal when considering BW alone. Plasma Mineral Results (Experiment 1) Plasma Ca and Mg were the only macromineral concentrations affected by collection date of sampling (P<0.05), and no plasma macromin erals showed a difference among treatments (Table 3-3). Plasma Ca decreased (P<0.05) from d84 to the end of the experiment in treatment 1, but were in the normal range (>8mg/dL) during th e entire experiment. The other treatments had no collection date differences in plasma Ca. In plasma Mg, a collection date effect was found only for treatment 1 (P<0.05). Magnesium levels increased (P<0.05) from d0 to d84 and then decreased (P<0.05) at the end of the experiment (T able 3-3). However, no treatment effects were
39 Table 3-2. Effect of Aluminum-water treatmen t residuals (Al-WTR) and P supplementation on Experiment 2 Steer Body Weights (kg) 1-3 Day Trt 0 70 145* Mean SD 1 175a 182b 232c 196 31.1 2 159a 170b 218c 182 31.4 3 178a 186b 241c 202 34.3 4 165a 176b 235c 192 37.6 SD 8.81 7.00 9.75 8.41 a,b Means with same letters within rows are not different (P>0.05). At experiment termination, treatment 2 was lower (P<0.05) than treatment 3. 1 Data represent treatment least square means and standard deviations. 2 Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR. 3 Animals received free-choice mineral suppleme nt with the following minerals: Ca, 16-18%; P, 8% (treatments 2 and 4 only); NaCl, 2327%; Mg, 2%; Fe, 1%; Co, 50 mg/kg; Cu, 500 mg/kg; I, 50 mg/kg; Mn, 2000 mg/ kg; Se, 26 mg/kg; and Zn, 4000 mg/kg. 4 Average mineral consumption for each treatment was as follows: 1) 48 g/animal/d; 2) 67 g/animal/d; 3) 53 g/anim al/d; 4) 62 g/animal/d.
40 shown at any time and no other treatments showed collection date effects. Magnesium plasma concentrations ranged from 2.30 mg/dL to 2.70 mg/dL and were considered to be in the normal range (>1.7 mg/dL). There were no treatment or collection date differences in plasma P concentrations (P>0.05). Phosphorus levels ra nged from 5.42 mg/dL to 6.68 mg/dL and were in the normal range above the critical level of 4.5 mg/dL throughout experiment 1 (Table 3-3). Zinc was the only micromineral to show differe nces (P<0.05) in date of collection throughout experiment 1, but there were no treatment differen ces (P>0.05) (Table 3-3). In treatments one and three, Zn levels increased gradually from the start of the treatment until the end of the experiment. In treatment four, Zn levels increased (P<0.05) from d84 until d148 (1.84 to 2.10 g/mL, repectively). Zinc plasma concentrations never reached a level n ear that suggested as a deficiency (<0.60 g/mL). Plasma Cu concentrati ons were not affected by treatment (P>0.05) or date (P>0.05) throughout the experiment (Table 33). Across treatments, mean plasma Cu levels ranged from 0.77-0.99 g/ml and were above the cr itical concentration of 0.65 g/mL. There were no treatment or collection date differen ces (P>0.05) among treatments in plasma Al concentrations (Table 3-3). Most of the samp les analyzed for Al were 0.02 g/mL, with a detection limit of 0.02 g/mL. Plasma Mineral Results (Experiment 2) Calcium and Mg plasma concentrations were again the only macrominerals to show an effect by collection date (P<0.05), and no plas ma macrominerals had a difference (P>0.05) among treatments (Table 3-4). Calcium increased significantly (P<0.05) from d0 to d70 in all 4 treatments and remained higher than at d0 until the end of experiment 2. Plasma Ca never reached a deficient conc entration (<8 mg/dL).
41 Table 3-3. Plasma mineral concentrations as affected by Al-WTR and P supplementation (Experiment 1)1,2 Trt Day 0 Day 84 Day 148 Means SD Ca m g /dL 1 12.0a 12.5a10.5 b 11.7 1.05 2 12.1 11.8 11.4 11.8 0.37 3 12.2 11.7 11.7 11.9 0.30 4 12.4 11.7 11.6 11.9 0.45 SD 0.17 0.39 0.55 0.10 Mg, mg/dL 1 2.30a 2.70b 2.07a 2.36 0.32 2 2.47 2.50 2.44 2.47 0.03 3 2.40 2.42 2.33 2.38 0.05 4 2.53 2.65 2.38 2.52 0.14 SD 0.10 0.13 0.16 0.08 P, mg/dL 1 6.65 6.11 5.42 6.06 0.62 2 6.44 6.27 5.49 6.07 0.51 3 5.89 6.02 6.68 6.20 0.42 4 6.07 5.61 5.51 5.73 0.30 SD 0.35 0.28 0.60 0.20 Al, g/mL 1 0.02 0.02 0.02 0.02 0.00 2 0.01 0.02 0.02 0.02 0.00 3 0.02 0.02 0.02 0.02 0.00 4 0.02 0.02 0.02 0.02 0.00 SD 0.01 0.00 0.00 0.00 Cu, g/mL 1 0.89 0.81 0.77 0.82 0.06 2 0.94 0.82 0.77 0.84 0.09 3 0.99 0.82 0.84 0.88 0.09 4 0.93 0.80 0.89 0.87 0.07 SD 0.04 0.01 0.06 0.03 Zn, g/mL 1 1.79a 1.85ab 2.04b 1.89 0.13 2 1.65 1.82 1.75 1.74 0.09 3 1.73a 1.89ab 2.02b 1.88 0.15 4 1.84a 1.84a 2.10b 1.93 0.15 SD 0.08 0.03 0.16 0.08 a-c Means with same letters within rows are not different (P<0.05). 1 Data represent treatment means and overall standard deviations. 2 Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR.
42 Magnesium concentrations increased from d0 to d70 in the first three treatments and then continued at high levels to the end of experiment 2 (Table 3-4). No collection date effects were shown in Mg concentrations in treatment 4. No treatment effects were shown (P>0.05) at any time in plasma Mg. Plasma Mg concentrations ranged from 1.73 to 2.34 mg/dL and some values were considered to be slightly below the normal range of 1.8-3.2 mg/dL. Serum P was not affected (P>0.05) by treatment or collection date and concentrations were above critical levels (>4.5mg/dL) throughout the experiment. Phosph orus levels ranged from 4.66 to 5.67 mg/dL (Table 3-4). Plasma Zn did not show differences (P>0.05) among treatments, but was lower (P<0.05) for the final date of collection for all treatments th an the previous two collections (Table 3-4). In treatment 3, plasma Zn was higher (P<0.05) on d70 than on d0 or d145. Plasma Cu concentrations did not show any treatment di fferences (P>0.05) throughout the experiment (Table 3-4). Across treatments, plasma Cu le vels ranged from 0.72-0.97 g/ml. In treatments 1 and 2, without Al-WTR, Cu levels did increa se at d70, and then decreased at d145 (P<0.05). Plasma Cu was in the normal range (>0.65 g/m L) throughout the experiment. There were no treatment or collection date differences for plasma Al concentrations; with all samples analyzing 0.02-0.03 g/mL. Plasma Mineral Discussion Plasma macrominerals (Ca, Mg, and P) were high er, in general, in experiment 1. Yet, the microminerals (Al, Cu, and Zn) were generally higher in experi ment 2. Currently, there is no evidence to explain this finding. Cunha et al. (1964) reported that values of 10-12 mg/dL of Ca in plasma are normal for healthy cattle, with deficiency occurring at levels below 8 mg /dL. Later, the NRC (1996)
43 Table 3-4: Plasma mineral concentrations as affected by Al-WTR and P supplementation (Experiment 2)1,2 Trt Day 0 Day 70 Day 145 Means SD Ca m g /dL 1 9.03a 11.1 b 10.4 b 10.2 1.06 2 8.44a 9.74b 10.2b 9.45 0.90 3 8.39a 10.5b 10.2b 9.71 1.15 4 9.19a 10.7b 10.5b 10.1 0.81 SD 0.41 0.57 0.15 0.35 Mg, mg/dL 1 2.01a 2.33b 2.34b 2.23 0.15 2 1.73a 2.15b 2.29b 2.06 0.24 3 1.80a 2.25b 2.24b 2.10 0.21 4 2.14 2.20 2.26 2.20 0.05 SD 0.19 0.08 0.04 0.08 P, mg/dL 1 5.26 5.08 4.99 5.11 0.14 2 4.66 4.96 5.06 4.89 0.21 3 5.17 5.67 5.01 5.28 0.34 4 4.94 5.75 5.60 5.43 0.43 SD 0.27 0.40 0.29 0.23 Al, g/mL 1 0.02 0.02 0.02 0.02 0.00 2 0.03 0.03 0.03 0.03 0.00 3 0.02 0.02 0.02 0.02 0.00 4 0.02 0.02 0.02 0.02 0.00 SD 0.01 0.01 0.01 0.01 Cu, g/mL 1 0.72a 0.90b 0.81ab 0.81 0.09 2 0.76a 0.97b 0.74a 0.82 0.13 3 0.78 0.90 0.83 0.84 0.06 4 0.77 0.76 0.84 0.79 0.04 SD 0.03 0.09 0.05 0.02 Zn, g/mL 1 1.88a 2.13a 1.47b 1.83 0.33 2 2.10a 2.21a 1.58b 1.96 0.34 3 1.97a 2.42b 1.45c 1.95 0.49 4 2.01a 2.19a 1.48b 1.89 0.37 SD 0.09 0.13 0.06 0.06 a-c Means with same letters within rows are not different (P<0.05). 1 Data represent treatment means and overall standard deviations. 2 Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR.
44 mentioned that blood Ca concentration is not a g ood indicator of Ca stat us, because levels are maintained between 9-11 mg/dL by homeostati c mechanisms (parathyroid hormone, calcitonin, and the active form of vitamin D), which regu lates Ca absorption, reabsorption, and resorption from bone. Plasma Ca levels stayed above the deficient range in both experiments. Plasma P concentrations were higher in e xperiment 1 than experiment 2 ( 6.02 vs. 5.18 mg/dL). Plasma P concentrations consisten tly below 4.5 mg/dL indicate a P deficiency (McDowell, 2003). In both experi ments, P levels were normal to low, but never reached a level of deficiency at any point. Therefore, the Al in the Al-WTR did not complex with P enough to cause a deficiency in the cat tle in either experiment. Serum Mg values are often used to assess th e Mg status of animals (Miller et al., 1972). Underwood (1981) considered the normal range of serum Mg in cattle to be 1.8-3.2 mg/dL, and found serum Mg concentrations below 1.7 mg/d L in cattle suffering from hypomagnesemic tetany. McDowell and Arthington (2005) consider the critical level in serum to be 1 to 2 mg/dL. Magnesium levels ranged from 1.73 to 2.70 mg/dL for both experiments, and never reached a deficient range. Plasma Zn results showed no treatment effects in either years. It ha s been suggested that deficiency occurs when plasma levels are below 0.6-0.8 g/mL (McDowell, 2003). All of the plasma samples remained well above the Zn critical range for both experiments. The Cu concentrations in various fractions of blood are regularly used when evaluating the Cu status in ruminants. Plasma Cu concentratio ns were not affected by collection date in any of the treatments for both experiments. The critical level for plasma is estimated to be 0.65 g/mL (McDowell and Arthington, 2005). In both experime nts, the Cu concentrations stayed in the normal range.
45 For both experimental years there were no treatme nt or date differences (P>0.05) in plasma Al concentrations. In both experiments, the Al plasma concentrations were very low (0.02 g/mL, on average), indicating that the Al in Al-WTR may be unava ilable to the animal and safe to use on pastures to reduce the P environmental problem. Liver Mineral Results (Experiment 1) In experiment 1, Cu ranged from 171.1-393.5 mg /kg DMB (Table 3-5). There were also changes (P<0.05) in liver Cu as the experime nt progressed, and differences among treatments were shown pre-experiment. However, there was no treatment effect (P>0.05) in liver Cu. In treatments two and four, liver Cu increased from d0 to d84 and then decreased to concentrations not different than d0. During experiment 1, liver Cu never fell below the critical level (>25 to 75 mg/kg DMB). Liver Al values ranged from 67.3 to 185 mg/kg (Table 3-5). For treatments 1, 3 and 4, liver Al was higher (P< 0.05) at d84 compared to d0 and d148. Aluminum concentrations were higher (P<0.05) for treatment 2 than treat ment 4 at d0 (67.3 vs. 126 mg/kg, respectively). There were no other treatment differences in liver Al. Liver P (P>0.05) was not affected by treatm ent during the experiment. In treatment 4, liver P concentrations increased from d0 to d84. There we re no collection date effects in treatments 1-3. Phosphorus concentrations range d from 0.82 to 0.95% in experiment 1 (Table 35). Liver Mineral Results (Experiment 2) Similar to experiment 1, liver mineral concen trations of Cu were in the normal range (Table 3-6). There were no treatment or collectio n date differences (P<0.05) for these liver Cu or Al concentrations. In e xperiment 2, Cu liver concentr ations ranged from 303.9-378.9 mg/kg DMB (Table 3-6). Liver Al concentrations ra nged from 138 to 162 mg/kg. There were no other treatment or collection date effects s een during the experiment for liver Al.
46 Table 3-5. Liver Al, Cu, and P concentrations (DMB) as affected by Al-WTR application to pastures and P supplementation (Experiment 1)1,2 Trt Day 0 Day 84 Day 148 Means SD P, % 1 0.82 0.95 0.89 0.89 0.07 2 0.79 0.93 0.93 0.88 0.08 3 0.78 0.91 0.90 0.86 0.07 4 0.67a 0.95b 0.92b 0.85 0.15 SD 0.07 0.02 0.02 0.02 Al, mg/kg* 1 100a 138b 114a 117 19.2 2 126a 141a 81.3b 116 31.1 3 115a 185b 99.8a 133 45.4 4 67.3a 141b 104a 104 36.9 SD 25.5 22.5 13.7 11.9 Cu, mg/kg* 1 246 314 327 295 43.3 2 240a 393b 281a 305 79.6 3 342 316 238 299 54.4 4 171a 376b 264a 270 103 SD 70.3 40.7 37.4 15.4 a,b Means with same letters within rows are not different (P<0.05). Pre-experiment differences (P< 0.05) were: 1) Al was different for treatments 2 and 4; 2) Cu was different for treatments 3 and 4. 1 Data represent treatment means and overall standard deviations. 2 Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR.
47 Liver P was lower (P<0.05) at d70 in treatment 3 than in tr eatments 1, 2, and 4. Liver P also increased (P<0.05) thr oughout the experiment for trea tment two only. Phosphorus concentrations ranged from 0.77 to 1.06% in experiment 2 (Table 3-6). Liver Mineral Discussion On average, mineral concentrations (P, Al, and Cu) in experiment 2 were higher than experiment 1. There were fewer collection date eff ects seen in year 2 for all minerals analyzed. In healthy ruminants, liver Cu concentr ations should be between 100-400 mg/kg DMB (McDowell, 2003); the criti cal levels in liver are estimated to be 25-75 mg/kg DMB (McDowell and Arthington, 2005). In both experiments, liver Cu concentrations were in the normal range, with year 1 concentrations remain ing slightly lower than year 2. Although liver concentrations of Al and P are not good indicato rs of mineral status, the minerals were assessed mainly to look at possi ble treatment differences. As with liver Cu, differences were seen in Al a nd P during the experiment, usually reflecting the change in season. Liver Al levels were too low to cause any toxic effects in both experiments. Liver Al in both experiments was slightly above 4.1 mg/kg; this is based on limited analysis reported for several species (Alfrey, 1986). The differences in liver Al during the experime nt did not give any significant conclusions about any long-term treatment effect. Bone Mineral Results (Experiment 1) There were no treatment differences (P>0.05) or collection date trends in bone P, Mg, Ca, and Al mineral concentrations at experiment term ination (Table 3-7). Bone P was slightly below the average concentration of 17% (ash basis) for all treatments, but not low enough to be considered a deficiency (Tab le 3-7). Bone Mg was normal throughout the experiment, ranging from 0.63% to 0.75%. Bone Ca was normal (>37.6 %), ranging from 42.41% to 47.73%, with no treatment effects shown. Bone Al con centrations ranged from 87.0 to 130 mg/kg.
48 Table 3-6. Liver Al, Cu, and P concentrations (DMB) as affected by Al-WTR application to pastures and P supplementation (Experiment 2)1,2 Trt Day 0 Day 70 Day 145 Means SD P, %* 1 0.93 0.99 0.97 0.96 0.03 2 0.85a 1.01ab 1.06b 0.97 0.11 3 1.01 0.77 1.00 0.93 0.14 4 0.95 0.99 0.88 0.94 0.06 SD 0.07 0.11 0.08 0.02 Al, mg/kg 1 144 138 157 146 9.71 2 145 148 156 150 5.69 3 148 157 157 154 5.20 4 151 142 162 152 10.0 SD 3.16 8.26 2.71 3.42 Cu, mg/kg 1 364 379 364 369 8.67 2 312 309 409 343 56.5 3 341 328 304 342 18.8 4 351 327 327 335 13.9 SD 22.1 30.1 45.9 14.9 a,b Means with same letters within rows are not different (P<0.05). On d70 for liver P, treatment 3 was lo wer (P<0.05) than the other treatments. 1 Data represent treatment means and overall standard deviations. 2 Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR.
49 Bone Mineral Results (Experiment 2) No treatment or collection date differences (P >0.05) were seen duri ng the course of the experiment in any of the measured Ca, P, Mg and Al concentrations. Bone P ranged from 12.11 to 12.53%, below the critical range of 17% (Table 3-8). On average, bone Ca was lower than experiment 1, ranging from 38.53% to 41.68%. Bone Mg was normal throughout the experiment, ranging from 0.60% to 0.64%. Bone Al means ranged from 65.2 to 83.3 mg/kg. Bone Mineral Discussion All bone mineral concentrations were higher in experiment 1. The Al-WTR treatments with and without supplemental P had no e ffect (P>0.05) on bone Ca, P, Mg, and Al concentrations for both experiment. The cri tical level for bone Ca (ash-basis) is 37.6% (McDowell and Arthington, 2005). Bone Ca con centrations were normal to low in both experiments and never reached a deficient range. McDowell and Arthington (2005) suggest that th e critical level for P on an ash basis is 17.6%. In experiment 1, the bone P was slightly be low the critical level. In experiment 2, the bone P fell below the critical level throughout the experiment. It could be assumed that the low concentrations of P are due to the Al in the Al-WTR complexi ng the P and making it unavailable. However, low levels were seen pre-experiment as well, and there were no differences in the treatments without Al-WTR that also contained P in the mineral supplement. Therefore, it can be concluded that unknown f actors caused the low bone P concentrations and not the Al in the Al-WTR Forage Mineral Results (Experiment 1) Mean forage Ca varied from 0.26% to 0.42% throughout the experiment (Table 3-9). All treatment and control means of forage Ca were below the critical level (0.35%) for the non AlWTR group until November. Forage Ca concentrati ons were below the cr itical level after May
50 Table 3-7. Effects of Al-WTR and P supplementati on on bone mineral concentrations (ash basis) of Ca, P, Mg, and Al (Experiment 1)a-c Treatment Means 1 2 3 4 Means SD Ca, % 42.4 47.7 42.9 43.5 44.2 2.43 Mg, % 0.67 0.75 0.64 0.63 0.67 0.05 P, % 16.2 16.9 16.5 16.1 16.4 0.38 Al, mg/kg 125 90.9 130 87.0 108 22.4 a Data represent least squared means and overa ll standard deviations; n = 9 per treatment. b No differences (P>0.05) among treatments or collection periods. c Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR. Table 3-8. Effects of Al-WTR and P supplementati on on bone mineral concentrations (ash basis) of Ca, P, Mg, and Al (Experiment 2)a-c Treatment Means 1 2 3 4 Means SD Ca, % 41.7 38.5 41.2 41.3 40.7 1.45 Mg, % 0.64 0.60 0.61 0.64 0.63 0.02 P, % 12.5 12.3 12.2 12.1 12.3 0.19 Al, mg/kg 65.2 83.3 65.2 68.2 70.5 8.67 a Data represent least squared means and overa ll standard deviations; n = 9 per treatment. b No differences (P>0.05) among treatments or collection periods. c Treatments were as follows: 1) controlno Al-WTR application with steers receiving commercial free-choice mineral supplement but no P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR and 4) treatment 2 with Al-WTR.
51 for the Al-WTR group. Mean forage Ca conc entrations did not vary (P>0.05) between the no Al-WTR group and the Al-WTR group except in N ovember. In November, forage where AlWTR had been applied was lower (P<0.05) in Ca than the non-WTR treated forages. Forage K concentrations (Table 3-9) were high and adequate for both Al-WTR and no AlWTR treatments, exceeding the 0.60% critical level at all sampling times, except in the month of December, where they fell dramatically (P<0.05 ). There were no treatment effects (P>0.05) evident throughout the grazing s eason. All treatment means for forage Na (Table 3-9) concentrations were well below the critical limit of 0.06%. Although there were treatment effects (P<0.05) in November, they were sma ll and did not persist with time. Forage Mg concentrations ranged from 0.13 to 0.20% in experiment 1 and were all above the critical level (0.10%). There were no collec tion date or treatment effects (Table 3-9). Both treatment groups produced adequate P concentrations (>0.18 %) until August, and various Al-WTR and no Al-WTR treatments were borderline adequate to deficient during the remainder of the experiment. Phosphorus c oncentrations ranged fr om 0.06 to 0.23% and decreased (P<0.05) steadily as the expe riment progressed in both treatments. Forage Al concentrations were different (P<0.05) depending on colle ction date, however, there was no discernable pattern (Table 3-9). There was a treatm ent difference (P<0.05) in July, the second month after Al-WTR ap plication, where the Al-WTR tr eatment resulted in a higher Al mean concentration than th e control (65.3 vs. 45.9 mg/kg). Forage Cu means were low for both trea tment groups (with or without Al-WTR application) at each of the samplings; forage Cu was below beef cattle requirements (10 mg/kg). None of the forage samplings were different (P>0.05) in forage Cu as a result of treatment (Table 3-9). Copper concentrations were generally high er in the early season, wi th treatment means for
52 Table 3-9. Forage minerals as affected by water treatment residuals (Experiment 1)1-5 Trt May Jul Aug Sep Oct Nov Dec Means SD Ca % 1 0.38a 0.30 b 0.27 b 0.27 b 0.28 b 0.32 b 0.31 b 0.30 0.04 2 0.33ad 0.27ac 0.31acd 0.27ac 0.26c 0.42b 0.35d 0.32 0.06 SD 0.04 0.02 0.03 0.00 0.01 0.07 0.03 0.01 K, % 1 1.38a 1.43a 1.33ad 0.82bd 1.09ad 2.14c 0.43b 1.23 0.50 2 1.51a 1.36a 1.18a 1.02a 1.09a 2.09b 0.44c 1.24 0.47 SD 0.09 0.05 0.11 0.14 0.00 0.04 0.01 0.01 Mg, % 1 0.18 0.19 0.16 0.16 0.18 0.16 0.13 0.17 0.02 2 0.17 0.20 0.19 0.15 0.17 0.19 0.15 0.17 0.02 SD 0.01 0.01 0.02 0.01 0.01 0.02 0.01 0.00 Na, % 1 0.02bc 0.02acd 0.02a 0.02a 0.03c 0.03b*0.01d 0.02 0.01 2 0.02c 0.02ac 0.02c 0.01ad 0.02c 0.04b*0.01d 0.02 0.01 SD 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.00 P, % 1 0.23a 0.23a 0.15b 0.14b 0.14b 0.14b 0.06c 0.16 0.05 2 0.22a 0.21a 0.17b 0.12b 0.14b 0.15b 0.06c 0.15 0.05 SD 0.01 0.01 0.01 0.01 0.00 0.01 0.00 0.01 Al, mg/kg* 1 35.0b 65.3a 17.3b 36.1b 18.7b 26.2b 17.7b 30.9 15.8 2 25.1ab 31.9ab 15.8b 28.9ab 39.2a 37.4a 20.1ab 28.3 8.00 SD 7.00 23.6 1.06 5.09 14.5 7.92 1.70 1.84 Cu, mg/kg 1 9.69a 8.17ac 8.75a 5.76b 6.18b 6.87bc 7.95ac 7.66 1.31 2 8.41a 8.23a 7.52a 5.32b 5.55b 8.48a 8.29a 7.39 1.27 SD 0.91 0.04 0.87 0.31 0.45 1.14 0.24 0.19 Fe, mg/kg 1 66.3a 59.1ac 33.3bd 34.3bd 35.4bd 54.9ac 42.1cd 44.5 12.48 2 43.9ac 43.1ac 33.7a 36.7ac 36.4ac 66.6b 52.4bc 44.7 10.66 SD 15.8 11.3 0.28 1.70 0.71 8.27 7.28 0.14 Mn, mg/kg 1 78.3 83.8 60.5 56.5 90.7 96.1 95.1 80.1 14.89 2 48.9 49.7 48.6 48.3 63.2 70.0 79.6 58.3 11.78 SD 20.8 24.1 8.41 5.80 19.4 18.5 11.0 15.4 Zn, mg/kg 1 34.4a 28.8ab 28.7ab 25.9abc 23.3bc 23.0bc 18.6c 26.1 4.73 2 43.9ace 43.1ad 33.7ace 36.7bce 36.4ac 66.6de 52.4ace 44.7 10.66 SD 6.72 10.1 3.54 7.64 9.26 30.8 23.9 13.2 a-d Means with same letter within ro ws are not different (P>0.05). In November for forage Ca, treatment with Al -WTR was lower (P<0.05) than the control. In July for forage Al, control treatment was lower (P<0.05) than treatment with Al-WTR. 1 Treatments were as follows: 1) Al-WTR; 2) Controlno Al-WTR. 2 Means represent 12 sample s per month per treatment. 3 Critical concentrations are as follow s: Ca, 0.35%; P, 0.18%; Mg 0.10%; K 0.60%; Na, 0.06%; Cu, 10.0 mg/kg; Fe, 50.0 mg/kg; Mn, 20.0 mg/ kg; Zn, 30.0 mg/kg (NRC, 1986; McDowell and Arthington, 2005). 4Water treatment residual contained 0.30% Fe, 7.8% Al, 0.11% Ca, 0.024% Mg, 0.30% P, 0.004% Mn, 0.73% S, 0.006% Cu, and 0.002% Zn. 5Dry Matter Basis.
53 both groups at their highest in May, after which there was a tre nd for Cu concentrations to decrease to very low levels from September through November. The range of forage Fe (Table 3-9) con centrations across all treatments was 33.3-66.6 mg/kg, with more than half of the means providi ng less than the requirement of 50 mg/kg. There was a trend for all pastures, with or without Al-WTR, to have lo wer Fe concentrations at the mid-season samplings, a condition that improved by seasons end. Forage Fe concentrations varied and were affected (P<0.05) by time. Forage Mn concentrations (Table 3-9) for the control and the treatment pastures far exceeded the minimum 20 mg/kg of diet at al l sampling times. They ranged from 48.3-96.1 mg/kg throughout the experiment and there we re no treatment effects (P>0.05). With the exception of the lowest Mn concentrations f ound in September, individual treatment means fluctuated moderately from month to month, with little apparent discerna ble pattern. During the last months (November and December), forage Mn was at its highest concentration. Cobalt and Mo were analyzed for only three sampling periods (May, August, and November), while one-third of samples collected each month were analyzed for Se. For those three elements, there were no treatment or sampling date differences (P>0.05). Cobalt concentrations averaged 0.04 0.04 mg/kg, rangi ng from 0.01 to 0.20 mg/kg. Over 99% of all the samples analyzed had Co concentrations le ss than the 0.1 mg/kg requirement. There was a trend for all treatment forages to increase in Co from May through August, and then decrease to November. All samples analyzed for Se were below the requirement of 0.1 mg/kg, and ranged from 0.02 to 0.08 mg/kg. Forage Mo concen trations ranged from 0.09 to 2.45 mg/kg and averaged 0.69 0.60 mg/kg and over half of the samples analyzed were below 1.5 mg/kg.
54 Forage Mineral Results (Experiment 2) There were no treatment effects (P>0.05) from Al-WTR application to pastures for any of the minerals analyzed in experiment 2 (Table 3-10 ). Mean forage Ca concentrations varied from 0.29% to 0.42% throughout the experiment, which is similar to year one data. All treatment and control means were at or slightly above the cri tical level (0.35%) for bot h treatments, except in June, where they were slightly below the requirement. All treatments produced low to adequate P c oncentrations except for treatment one in September, which fell to 0.15 % DM (<0.18%). Fo rage K (Table 3-10) was high and adequate for treatments, exceeding the 0.60% critical level at all sampling times. There were no treatment effects (P>0.05) for forage K throughout the gr azing season. All treatment means for forage Na (Table 10) concentrations were well below the cr itical limit of 0.06%, just as in year one. There were no treatment or collection date effects (P>0.05) in year 2 for Na. Forage Mg levels ranged 0.17 to 0.21% in experi ment 2. At all times, Mg concentrations were above the critical level of 0.10%. There were no collection date or tr eatment effects seen in the second experiment. There were no treatment differences (P>0.05) in experiment 2 for forage Al. However, there were collection date differences (P<0.05) in treatment 2 (with no Al-WTR). There was no discernable pattern as the experi ment progressed. Forage Al concentrations ranged from 21.3 to 37.7 mg/kg. There were no differences (P<0.05) among tr eatments in forage Cu during the six collection dates. Copper means were low for both treatments at each of the samplings, and below levels considered adequate for beef cattl e (10 mg/kg). Copper conc entrations ranged from 7.4 to 9.5 mg/kg across treatments. None of the co llection samplings were different (P<0.05) as a result of treatment (Table 3-10). Copper con centrations were genera lly higher in the early
55 season, with treatment mean s for all groups at thei r highest in May, after which there was a trend for Cu concentrations to decrea se to very low levels throughout the rest of the experiment. The range of forage Fe (Table 3-10) concen trations across all treatments was 39.5 to 58.5 mg/kg, with half of the means providing less than the 50 mg/kg, similar to experiment 1. Forage Fe concentrations varied and were a ffected (P<0.05) by the changing season. Forage Mn concentrations for the control a nd the treatment pastures far exceeded the minimum 20 mg/kg of diet at all sampling times (Table 3-10). No forage sample was deficient in Mn, with month means ranging from 55.7-142.4 mg /kg throughout the experiment and there were no month effects (P>0.05). Individual treatm ent means fluctuated moderately from month to month, with no apparent discernable pattern. Thirty-two forage samples were analyzed for Se, and there were no treatment or sampling date differences (P>0.05). Forage Se con centrations averaged 0.05 0.02 mg/kg. As in experiment 1, of all samples analyzed for Se were below the critical level of 0.1 mg/kg. Forage Se ranged from 0.01 to 0.03 mg/kg and they were lower than in experiment 1 on average. Forage Mineral Discussion Mean forage Ca concentrations were very si milar in both experiments. In November of experiment 1, forage from the Al-WTR treatment 1 had lower (P<0.05) Ca concentrations than the control (treatment 2). This same effect was seen in September of experiment 2. Similar forage Ca concentrations were reported in Florid a bahiagrass by Cuesta et al. (1993). In a central Florida study, Espinoza et al. (1991a) found Ca and P concentra tions in bahiagrass to be adequate for modest growth for beef cattle durin g most months. Flores et al. (1993) also found Ca in north Florida bahiagrass to be adequate for modest cattle gains. Similar to Ca requirements, dietary P require ments are based on the level of production for a given animal. Dietary P requirements for 300 kg growing and finishing beef cattle expected to
56 Table 3-10. Forage minerals as affected by water treatment residuals (Experiment 2)1-5 Trt May Jun Jul Aug Sep Oct Means SD Ca % 1 0.42 0.32 0.380.380.330.370.37 0.04 2 0.37 0.29 0.31 0.36 0.39 0.35 0.33 0.05 SD 0.04 0.02 0.05 0.01 0.04 0.01 0.03 K, % 1 1.49 1.39 1.33 1.31 1.23 1.21 1.33 0.10 2 1.42 0.96 1.14 1.40 1.58 1.45 1.33 0.23 SD 0.05 0.30 0.13 0.06 0.25 0.17 0.00 Mg, % 1 0.18 0.20 0.19 0.21 0.17 0.19 0.19 0.01 2 0.18 0.20 0.18 0.19 0.19 0.18 0.19 0.01 SD 0.00 0.00 0.01 0.01 0.01 0.01 0.00 Na, % 1 0.02 0.01 0.02 0.02 0.02 0.02 0.02 0.00 2 0.02 0.02 0.01 0.02 0.02 0.02 0.02 0.00 SD 0.00 0.01 0.01 0.00 0.00 0.00 0.00 P, % 1 0.20 0.19 0.19 0.19 0.15 0.17 0.18 0.19 2 0.21 0.21 0.19 0.19 0.18 0.17 0.19 0.02 SD 0.01 0.01 0.00 0.00 0.02 0.00 0.01 Al, mg/kg 1 23.4 24.7 26.3 21.3 33.7 30.3 26.6 4.61 2 26.2abc 30.8bce 23.2cd 27.5bdf 40.5ef 37.7be 31.0 6.80 SD 1.98 4.31 2.19 4.38 4.81 5.23 3.11 Cu, mg/kg 1 9.54 8.33 8.67 8.41 8.78 7.63 8.54 0.62 2 9.16 9.27 8.13 7.47 8.39 7.88 8.35 0.71 SD 0.27 0.66 0.38 0.66 0.28 0.18 0.13 Fe, mg/kg 1 50.8ab 47.2ab 54.5a 55.2a 48.4ab 39.5b 49.3 5.75 2 58.5a 53.8ac 44.8bc 42.2bc 43.8bc 41.0b 47.4 7.10 SD 5.44 4.67 6.86 9.19 3.25 1.06 1.34 Mn, mg/kg 1 92.0 69.1 84.7 64.8 88.2 142.4 90.2 27.76 2 55.7 58.9 40.6 74.1 90.1 93.3 68.7 20.77 SD 25.7 7.21 31.2 6.58 1.34 34.7 15.2 Zn, mg/kg 1 37.4acde 26.3be 31.5bc 19.8b 20.5bd 44.4c 30.0 9.72 2 25.5ab 24.9ab 21.0ab 29.1ab 15.7a 32.4b 24.8 5.90 SD 8.41 1.00 7.42 6.58 3.39 8.49 3.68 a-d Means with same letter within ro ws are not different (P>0.05). 1 Treatments were as follows: 1) Al-WTR; 2) Controlno Al-WTR. 2 Means represent 12 sample s per month per treatment. 3 Critical concentrations are as follow s: Ca, 0.35%; P, 0.18%; Mg 0.10%; K 0.60%; Na, 0.06%; Cu, 10.0 mg/kg; Fe 50.0 mg/kg; Mn, 20.0 mg/ kg; Zn, 30.0 mg/kg (NRC, 1986; McDowell and Arthington, 2005). 4Water treatment residual contained 0.30% Fe 7.8% Al, 0.11% Ca, 0.024% Mg, 0.3% P, 0.004% Mn, 0.73% S, 0.006% Cu, and 0.002% Zn. 5Dry Matter Basis.
57 gain 0.89 kg/d are 0.18% DM. (NRC, 1996). Using this as a guideline, both treatment groups produced adequate P concentrations until August/September for both experiments. These concentrations, regardless of treatment, were si milar to earlier reports (Espinoza et al., 1991a; Cuesta et al., 1993). Flores et al (1993) also found that P levels in grass were low and possibly limiting to cattle growth. Since P concentrations decreased as the experi ment continued in both years, it is questionable as to whether or not the complexing Al in Al-WTR is the culprit. Since P levels dropped more in experiment 1 when ther e as less WTR applied to the pastures, it can be inferred that the Al-WTR was not the primar y cause of the drop in forage P. Forage K levels did not drop in December like experiment 1 K levels, which fell dramatically (P<0.05). Cuesta et al., (1993) showed K varying throughout the season as both experiments did. However, expe riment 1 showed significant diffe rences (P<0.05) in forage K concentrations throughout the year, unlike experiment 2. Forage Mg levels were higher in experime nt 2 than in experiment 1 (0.19 and 0.17%, respectively). Magnesium concentrations were well above the critical level of 0.10% (NRC, 1996) for all treatments throughout the grazing seas on. Forage Mg concentrations were similar to those reported previously by Cuesta et al. (1993) in north Florida during both experiments. All forage Na concentrations were belo w the critical level of 0.06% during both experiments. Sodium deficiency in Florid a is well-documented, and the concentrations determined by these experiments are similar to earl ier reports by Salih et al (1988) and Cuesta et al. (1993) in central Florida. Espi noza et al. (1991b) also found that Na concentrations in forage generally provided less than half of the requirements. All forage Cu concentrations were below the critical level of 10 mg/kg in both experiments and were lower, on average, in experiment 1. Lo w forage Cu concentrations were also reported
58 by Merkel et al. (1990) and Espinoz a et al. (1991b) in north and cen tral Florida. Low forage Cu is of particular concern to cattl e producers in this region, as inad equate Cu in the diet can cause depressed growth, anemia, and a variety of nervous disorders (McDowell, 2003). There was a trend for all pastures, regardless of treatment, to have lower Fe concentrations towards the experiment termination, a conditi on that did not improve by seasons end like experiment 1 did. Forage Fe concentrations va ried throughout the experiments. Espinoza et al. (1991b) found variation in forage Fe concentration and a higher percentage of Fe deficient samples in a study conducted in central Florida. Experiment 2 forage Mn means were considerab ly higher than for the previous experiment. All forage Mn concentrations were well above the critical level of 20 mg/kg in both experiments. High dietary levels of Mn are not viewed as a pr oblem for grazing ruminants, as they can tolerate dietary levels as high as 1,000 mg /kg (McDowell and Arthington, 2005). Aluminum levels were similar in experiments 1 and 2 and varied by date (P<0.05) in all but treatment 1 of experiment 2. There is ve ry little forage Al analysis data; however Underwood and Suttle (1999) suggest uncontaminated forage Al to range from 50 to 100 mg/kg. For most samples reported for the two years, forage Al was less than 50mg/kg. Zinc levels also varied by date in both experiments and were similar between treatments (P>0.05). Low levels of Zn in soils, plants, and animal tissues have been reported through many tropical regions of the world (M cDowell and Arthington, 2005). Mo st Zn levels were below the critical level of 30 mg/k g in both experiments. Only a limited number of samples were analyzed for Co, Mo, and Se. Forage Mo varied, depending on factors such as soil Mo, soil pH and season. Molybdenum is an essential micronutrient required for plant growth. Fo rage Mo means were not variable between
59 treatments, and generally low throughout all sampling periods. Forage Mo concentrations ranged from 0.09 to 2.45 mg/kg and averaged 0.6 9 0.60 mg/kg. Forage Mo concentrations were similar to those found by Espinoza et al (1991b) in previous Florida studies. For ruminants, the effects of excess Mo are larg ely those of Cu deficiency (McDowell and Arthington, 2005). In the present st udy, forage Mo concentrations were too low to influence Cu deficiency. Over 99% of all Co samples taken were below the critical concentration of 0.1 mg/kg. Forage Co and Mo data were not taken in experiment 2. Forage Se can range from less than 0.05 to considerably over 100 mg/kg, but the sa mples analyzed in this study were extremely deficient and were all less than the requirement of 0.1 mg/kg. Summary and Conclusions Aluminum applied to the land has been show n to reduce soluble P concentrations and P losses from soils and thus can be used to reduc e environmental P contamination. Under grazing conditions, ruminants typically consume 10 to 15% of their DM intake as soil. The main question to be answered is whet her Al-WTR applied to pastures will be detrimental to grazing ruminants. Two experiments using grazing Hols tein steers were conducted to determine the effects of an Al water treatment residual (AlWTR) as pasture applications on mineral status (principally P) and cattle performance. A second objective was to evaluate the effects of these applied Al-WTR on forage mi neral concentrations. The experiments were in la te spring of consecutive year s, 2005 and 2006, and were 148 and 145d, respectively. For each experiment, 36 steer s were allotted (3/pasture) to 12 bahiagrass pastures of 12.0 ha and were provided mineral supplement. In experiment 1, one-half of the pastures received Al-WTR at a rate of 22.8 Mg /ha. In experiment 2, 53 Mg dry weight/ha additional Al-WTR was applied to the same pastures as in experiment 1. The treatments were in replicate and as follows: 1) cont rolno Al-WTR application with steers receiving free-choice
60 mineral supplement without P, 2) control with free-choice mineral supplement plus P, 3) treatment 1 with Al-WTR, and 4) treatment 2 w ith Al-WTR. Forage samples were taken on d0 and approximately every 28 d thereafter for 5 or 6 mo. Weights, blood, and liver biopsy were taken initially, at midpoint, and at termina tion, while bone biopsies were taken only at termination. The following minerals were analyz ed: plasmaCa, P, Mg, Al, Cu, and Zn; liverCu, Al, and P; boneCa, P, Mg, and Al; and fora geCa, P, K, Mg, Na, Al, Co, Cu, Fe, Mn, Se, and Zn. As the experiment progressed, there were in creases in body weight for all treatments (P<0.05) in both experiments. There were no differences (P<0.05) in body weight gains among treatments for experiment 1, but for experiment 2, cattle with the Al-WTR treatment without supplemental P had a higher average final body we ight (P<0.05) than the control treatment receiving supplemental P (241 vs. 218 kg). There were collection date plasma differences for Ca, Cu, Mg, and Zn, but no differences among treatments (P>0.05) for both experiments. There were only collection date and treatment differences for liver P during experiment 2. Li ver P increased (P<0.05) for treatment 2 as the experiment progressed and treatment 3 (Al-WTR plus P supplementation) was lower (P<0.05) than the other treatments. There were no treat ment differences (P<0.05) in bone minerals for both experiments. All forage mineral concentrations in experi ment 1 except Mg and Mn and only forage Al, Fe, and Zn in experiment 2 were affected by collection date. During both experiments, there were no treatment effects (P<0.05) from Al-WTR a pplications on forage mineral concentrations except in July, 2005 for Al and November, 2005 fo r Na. In July 2005, the second month after Al-WTR application, Al-WTR past ures were higher (P<0.05) in forage Al than not treated
61 pastures (65.3 vs. 31.9 ppm), but this trend did no t continue. The high value could be attributed to soil contamination on the forages during the collection. All plasma, bone, and liver minerals were above critical levels for grazing cattle for both years, with the exception of bone P, which wa s under the critical leve l of 17%. Manganese was the only forage that was above cattle requirement s at all collections. A few Ca samples were below 0.35%, and approximately 50% of forage P concentrations were below 18%. Forage K was below the critical level of 0.6% only in D ecember of experiment 1. Most forage Zn fell below 30 mg/kg. All forage Cu fell below the 10 mg/kg requirement, and more than 50% of forage Fe fell below 50 mg/kg during the cour se of the experiments. All Na forage concentrations were below the critical level of 0.06%. Over 99% of Co and Se samples fell below the critical level of 0.1 mg/kg. The quantities of Al-WTR applied to pastures in this study have previously been shown to reduce environmental P contamination to water s ources. Results from the present experiment demonstrate that the Al-WTR app lications had little or no effect on animal status of P or any other mineral analyzed. Likewise, Al-WTR had minimal effect on forage mineral concentrations. Lack of Al-WTR application effects on cattle mi neral status and production was likely due to low bioavailability and amorphous nature of Al from Al-WTR. In these two experiments, it has been shown that Al-WTR from the Bradent on, FL water treatment plant and similar Al-WTR is safe to use on pastures in low to moderately high levels to help alleviate the environmental P problem.
62 APPENDIX CHEMICAL COMPOSITION OF FORAGES Table A-1. Chemical composition of bahiagrass without Al-WTR application for Experiments 1 and 2a Experiment 1 Experiment 2 Component May September May September DM,% 91.0 91.2 91.6 91.3 CP,% 16.1 10.3 13.9 10.3 ADF,% 30.2 39.1 30.0 38.7 NDF,% 60.2 68.9 60.8 65.0 NFC,% 11.8 8.4 13.2 11.9 TDN,% 55.5 54.0 56.0 54.5 a Data means shown for dry matter (DM), crude pr otein (CP), acid detergen t fiber (ADF), neutral detergent fiber (NDF), non-fiber carbohydrate (N FC), and total digestible nutrients (TDN).
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72 BIOGRAPHICAL SKETCH Rachel Kristin Pratt was born in Weymout h, Massachusetts. She attended some grade school in Massachusetts and then moved to Florida at the age of 8. Rachel finished grade school at the Canterbury School of Florida and attend ed high school at St. Pe tersburg Catholic High School in Florida until 2001. She earned her bachelors degree in animal biology at the University of Florida in 2005 a nd her masters degree in 2007.