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Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. 8 Minimizing Nutrient Excretion Maximization of individual pig performance traditionally has been the goal of swine producers and nutritionists. Diets are generally formulated to achieve this goal with little or no regard for the amount of nutrients excreted. Consequently, oversupplementation of diets with nutrients to ensure maximum pig performance results in excessive amounts of excreted nutrients in feces and urine. Because of its relatively high content of nitrogen, phosphorus, potassium, and other nutrients, manure is an excellent fertilizer when applied to land. During the past decade, there has been little change in total number of hogs produced in the United States, but the number of large swine units and the intensity of production has sharply increased. As a result, large amounts of manure are produced on a much smaller land area. Distribution and disposal has become a problem. The application of excessive amounts of manure to land can potentially lead to surface and ground water contamination and to the accumulation of minerals in the soil. Of the nutrients present in manure, nitrogen, phosphorus, sodium, potassium, copper, and zinc cause the greatest concern. In some areas, nitrogen is used as the basis to regulate the amount of manure that can be applied to the land. However, evidence is accumulating which suggests that phosphorus will be the nutrient that limits land application of manure in the more intensive swine producing areas. For example, Barker and Zublena (1995) reported that in North Carolina, animal manure could provide about 20 percent of the nitrogen and 66 percent of the phosphorus requirements of all non-legume agronomic crops and forages produced in that state. Three of the 100 counties surveyed had enough manure to exceed the nitrogen requirements of their crops, and 18 counties had enough manure to exceed the phosphorus requirements of crops. Soil analyses of a Sampson County (North Carolina) bermudagrass pasture that was fertilized with swine lagoon effluent to satisfy nitrogen requirements showed approximately a fourfold increase in phosphorus and zinc, a onefold increase in potassium, and a threefold increase in copper to a depth of 91 cm during the three-year period of application (Mueller et al., 1994). These findings may well be representative of other regions of the United States. The overall quality of water, both surface water and ground water, can be negatively affected by applying excess nitrogen and phosphorus, and perhaps other nutrients, to soil. Excess nitrogen application can lead to increases in nitrate content of ground water and to potential runoff of nitrate into surface water. Excess phosphorus application results in excess buildup of phosphorus in the soil. While phosphorus is adsorbed onto soil particles and does not leach into ground water, it can erode (along with soil particles) into streams, lakes, and rivers. Phosphorus is the most limiting nutrient that regulates aquatic plant growth (Pierzynski et al., 1994; Sharpley et al., 1994), so when it is added to bodies of surface water, phosphorus stimulates growth of algae and other aquatic vegetation. Decomposition of such vegetation can lead to a general deterioration of water quality, a process called "eutrophication" (Crenshaw and Johanson, 1995). To prevent potential pollution by nitrogen and phosphorus, governments in many countries have passed legislation requiring nutrient management plans for each farm, so that land application of manure can be properly controlled (Hacker and Du, 1993). Even in the best situation, pigs do not utilize 100 percent of nutrients consumed. A review of balance data for pigs fed commercial feedstuffs indicates the following apparent utilization values (as percent of intake): 30 to 55 for nitrogen; 30 to 50 for calcium; 20 to 50 for phosphorus; 5 to 20 for potassium; 10 to 25 for sodium; 15 to 30 for magnesium; 5 to 30 for copper; 5 to 30 for zinc; 5 to 10 for manganese; and 5 to 30 for iron (Kornegay and Harper, 1997). Therefore, the percentages of intake excreted are 45 to 60 percent of nitrogen; 50 to 80 percent of calcium and phosphorus; and 70 to 95 percent of potassium, Page 103 FRONT MATTER (R1-R20) OVERVIEW (1-2) 1 ENERGY (3-15) 2 PROTEINS AND AMINO ACIDS (16-30) 3 MODELS FOR ESTIMATING ENERGY AND AMINO ACID REQUIREMENTS (31-46) 4 MINERALS (47-70) 5 VITAMINS (71-89) 6 WATER (90-96) 7 NONNUTRITIVE FEED ADDITIVES (97-102) 8 MINIMIZING NUTRIENT EXCRETION (103-106) 9 DIET FORMULATION (107-109) 10 NUTRIENT REQUIREMENT TABLES (110-123) 11 COMPOSITION OF FEED INGREDIENTS (124-142) APPENDIX 1 (143-147) APPENDIX 2 (148-149) APPENDIX 3 (150-152) APPENDIX 4 (153-170) APPENDIX 5 (171-178) AUTHORS (179-180) INDEX (181-192)

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--> 8 Minimizing Nutrient Excretion Maximization of individual pig performance traditionally has been the goal of swine producers and nutritionists. Diets are generally formulated to achieve this goal with little or no regard for the amount of nutrients excreted. Consequently, oversupplementation of diets with nutrients to ensure maximum pig performance results in excessive amounts of excreted nutrients in feces and urine. Because of its relatively high content of nitrogen, phosphorus, potassium, and other nutrients, manure is an excellent fertilizer when applied to land. During the past decade, there has been little change in total number of hogs produced in the United States, but the number of large swine units and the intensity of production has sharply increased. As a result, large amounts of manure are produced on a much smaller land area. Distribution and disposal has become a problem. The application of excessive amounts of manure to land can potentially lead to surface and ground water contamination and to the accumulation of minerals in the soil. Of the nutrients present in manure, nitrogen, phosphorus, sodium, potassium, copper, and zinc cause the greatest concern. In some areas, nitrogen is used as the basis to regulate the amount of manure that can be applied to the land. However, evidence is accumulating which suggests that phosphorus will be the nutrient that limits land application of manure in the more intensive swine producing areas. For example, Barker and Zublena (1995) reported that in North Carolina, animal manure could provide about 20 percent of the nitrogen and 66 percent of the phosphorus requirements of all non-legume agronomic crops and forages produced in that state. Three of the 100 counties surveyed had enough manure to exceed the nitrogen requirements of their crops, and 18 counties had enough manure to exceed the phosphorus requirements of crops. Soil analyses of a Sampson County (North Carolina) bermudagrass pasture that was fertilized with swine lagoon effluent to satisfy nitrogen requirements showed approximately a fourfold increase in phosphorus and zinc, a onefold increase in potassium, and a threefold increase in copper to a depth of 91 cm during the three-year period of application (Mueller et al., 1994). These findings may well be representative of other regions of the United States. The overall quality of water, both surface water and ground water, can be negatively affected by applying excess nitrogen and phosphorus, and perhaps other nutrients, to soil. Excess nitrogen application can lead to increases in nitrate content of ground water and to potential runoff of nitrate into surface water. Excess phosphorus application results in excess buildup of phosphorus in the soil. While phosphorus is adsorbed onto soil particles and does not leach into ground water, it can erode (along with soil particles) into streams, lakes, and rivers. Phosphorus is the most limiting nutrient that regulates aquatic plant growth (Pierzynski et al., 1994; Sharpley et al., 1994), so when it is added to bodies of surface water, phosphorus stimulates growth of algae and other aquatic vegetation. Decomposition of such vegetation can lead to a general deterioration of water quality, a process called "eutrophication" (Crenshaw and Johanson, 1995). To prevent potential pollution by nitrogen and phosphorus, governments in many countries have passed legislation requiring nutrient management plans for each farm, so that land application of manure can be properly controlled (Hacker and Du, 1993). Even in the best situation, pigs do not utilize 100 percent of nutrients consumed. A review of balance data for pigs fed commercial feedstuffs indicates the following apparent utilization values (as percent of intake): 30 to 55 for nitrogen; 30 to 50 for calcium; 20 to 50 for phosphorus; 5 to 20 for potassium; 10 to 25 for sodium; 15 to 30 for magnesium; 5 to 30 for copper; 5 to 30 for zinc; 5 to 10 for manganese; and 5 to 30 for iron (Kornegay and Harper, 1997). Therefore, the percentages of intake excreted are 45 to 60 percent of nitrogen; 50 to 80 percent of calcium and phosphorus; and 70 to 95 percent of potassium,

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--> sodium, magnesium, copper, zinc, manganese, and iron. The amount of a nutrient excreted can be influenced by several factors including quality, source, and level of the nutrient fed; the level and proportion of other nutrients; processing methods; age, class, and nutritional status of animals; and environmental factors. The use of highly digestible feedstuffs in diets is an effective means of reducing excretion of nitrogen and other nutrients. A portion of the nutrients excreted by the pig is a direct result of feeding excessive levels of nutrients. Results of surveys of the nutrient composition of diets indicate that diets commonly include excessive amounts of certain nutrients. Nutritionists call these excesses a safety factor included in the diet to allow for the variability of nutrient composition of feed ingredients or to compensate for uncertainty about the availability of the nutrients. Results of a survey by Cromwell (1989a,b) of phosphorus recommendations of several universities and feed companies showed that the average range of university recommendations was 110 to 120 percent of National Research Council (1988) requirements, whereas the average range of industry recommendations was 120 to 130 percent of these requirements. Spears (1996) reported that the mineral concentrations of sow and finishing pig diets analyzed by the North Carolina Feed Testing Laboratory were greatly in excess of requirements. The median levels as a percentage of National Research Council (1988) requirements for sow and finishing pig diets were the following: 161 and 192 percent, respectively, for calcium; 140 and 155 percent for phosphorus; 147 and 190 percent for sodium; 390 and 423 percent for potassium; 525 and 400 percent for magnesium; 440 and 667 percent for copper; 470 and 776 percent for iron; 770 and 3,100 percent for manganese; and 334 and 298 percent for zinc. Other surveys have reported similar findings of diets containing excess levels of nutrients. Excretion of minerals could be markedly reduced simply by reducing these excessive levels of nutrients in diets. Using high-quality protein sources with superior amino acid balance and formulating diets to achieve an ideal protein basis reduces nitrogen excretion. Lowering the dietary protein level and supplementing with certain crystalline amino acids also reduce nitrogen excretion. The reason is that both procedures reduce excesses of unneeded amino acids, which otherwise are degraded and excreted as urea nitrogen. Bridges et al. (1994) and Carter et al. (1996) showed that nitrogen excretion could be reduced by 30 to 40 percent by feeding corn–soybean meal diets in which the protein level was reduced by 4 percentage points and the diets supplemented with lysine, threonine, tryptophan, and methionine. Kerr and Easter (1995) suggested that for each one percentage unit reduction in dietary crude protein combined with amino acid supplementation, total nitrogen losses (fecal and urinary) could be reduced by approximately 8 percent. Conversely, the use of low-quality protein sources (e.g., hydrolyzed hog hair meal) markedly increases nitrogen excretion (Kornegay, 1978b). Also, the inclusion of high levels of crude fiber in the diet reduces the efficiency of nitrogen utilization (Kornegay, 1978a). In corn–soybean meal diets, two-thirds of the phosphorus is bound as phytic acid and is poorly available to the pig (Cromwell and Coffey, 1991); hence, much of the phosphorus is excreted. The amount excreted can be significantly decreased by the inclusion of microbial phytase in the diet, which releases some of the bound phosphorus, making it available to the pig (Jongbloed et al., 1992; Cromwell et al., 1993). Thus, the amount of inorganic phosphorus that must be added to meet the available phosphorus requirement is reduced, and phosphorus excretion can be decreased by 30 to 50 percent (Bridges et al., 1995; Carter et al., 1996). The magnitude of the response to microbial phytase has been shown to be influenced by the source of phosphorus, dietary level of available phosphorus, the amount of phytase added, and the ratio of calcium-to-phosphorus (Lei et al., 1994; Kornegay, 1996). Microbial phytase also releases calcium (Mroz et al., 1994; Radcliffe et al., 1995), zinc (Lei et al., 1993; Pallauf et al., 1994), as well as some amino acids (Kemme et al., 1995) that may be bound by phytic acid. High dietary levels of copper and zinc also significantly increase the amount of copper and zinc that is excreted. In a study by Apgar and Kornegay (1996), 71-kg barrows excreted 6.7 times more copper when fed diets containing 218 versus 32 ppm copper. Calculations based on data reported by Adeola et al. (1995) for 15- to 18-kg pigs fed diets with 23 or 123 ppm zinc from ZnSO4 indicated that pigs fed the low-zinc diet excreted 16 mg of zinc per day, whereas pigs fed the high-zinc diet excreted 61 mg of zinc per day, a 3.8-fold increase in the amount of zinc excreted. When diets containing 2,500 to 3,000 ppm zinc are fed to weanling pigs as is commonly done for growth promotion (Hahn and Baker, 1993; LeMieux et al., 1995; Smith et al., 1995; Hill et al., 1996), approximately 90 to 95 percent of the zinc will be excreted. Although these high levels would be fed for a period of only a few weeks, the total amount of zinc excreted could approach or exceed the total amount of zinc excreted during the entire growing-finishing period by pigs fed diets containing approximately 100 ppm zinc. Other strategies also have potential for reducing nutrients excreted. For example, improvements in overall feed efficiency can produce a reduction in excreted nutrients. Henry and Dourmad (1992) reported for growing-finishing pigs that for each 0.1 percentage unit decrease in feed-to-gain ratio, there was a 3 percent decrease in nitrogen excreted. Improvements in feed efficiency could result from improved genetics, improved environmental conditions, proper formulation of diets using high-quality ingre-

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--> dients, use of pelleting and fine grinding of feed, and proper feeder adjustment to reduce wastage. Harper (1994) estimated that a 5 percent level of feed waste resulted in an additional 327 g of nitrogen and 82 g of phosphorus excreted per animal. Nutrient requirements change as pigs increase in body weight. Thus, frequent changes in diet formulation can meet the nutrient needs of the pig more efficiently. Frequent adjustments in diets can result in reduced intake of nutrients and, thus, reduced excretion of nutrients. Phase feeding and separate-sex feeding are ways to meet the nutrient needs of growing and finishing pigs more precisely and reduce nitrogen excretion. A further point is that the efficiency of animal performance follows the principle of diminishing returns in response to nutrient input (Heady et al., 1954; Combs et al., 1991; Gahl et al., 1995). Heady et al. (1954) reported that in 14 of 16 years, swine diets formulated using the diminishing return concept would have produced greater profits than diets formulated for maximum gain. As the cost of disposing of nitrogen and phosphorus increases, the nutrient levels fed to pigs will probably decrease. In the future, nutritionists may formulate diets to achieve 95 to 98 percent rather than 100 percent of maximum response, because the benefit of adding a unit of nutrient increases at a decreasing rate, and nutrient costs increase at an increasing rate as the animal reaches maximum performance. The success of all strategies for reducing nutrients excreted is dependent on an accurate estimate of the nutrient requirements of the class of pigs in question and on the accuracy of compositional information for, and bioavailability of, feed ingredients. Recommended nutrient requirements for the different classes of pigs often vary and, in many cases, are only estimates for an ''average" animal under "average" environmental conditions. The estimated nutrient requirements may be influenced by the animal's genetic potential, feeding methods, environmental conditions, the ingredients used, and animal response criteria. With the exception of phosphorus and amino acids, nutrient requirements are generally based on total nutrients rather than available nutrients. The available nutrient requirement of pigs can be accurately met, assuming they are known, only if the compositional data of feed ingredients are expressed on available nutrient composition. Using more precise data on compositional and nutrient availability for feed ingredients and better defined requirements will allow nutritionists to formulate diets that more precisely meet the needs of the animal at the various stages of production. In summary, nutrients excreted can be reduced through proper nutrient management to improve the availability of nutrients and reduce excessive amounts that are fed. In the future, diet formulation will be integrated into a total production system with nutrient and manure management being its major components. The need for more careful nutrient management planning probably will increase in the future, as the intensity of the industry increases and as the concerns of the public increase. References Adeola, O., B. V. Lawrence, A. L. Sutton, and T. R. Cline. 1995. Phytase-induced changes in mineral utilization in zinc-supplemented diets for pigs. J. Anim. Sci. 73:3384–3391. Apgar, G. A., and E. T. Kornegay. 1996. Mineral balance of finishing pigs fed copper sulfate or a copper lysine complex at growth stimulating levels. J. Anim. Sci. 74:1594–1600. Barker, J. C., and J. P. Zublena. 1995. Livestock manure nutrient assessment in North Carolina. Pp. 98–106 in Proc. Seventh International Symposium on Agricultural and Food Processing Wastes. Sponsored by ASAE, Chicago, IL, June 18–20. Bridges, T. C., L. W. Turner, G. L. Cromwell, and J. L. Pierce. 1995. Modeling the effects of diet formulation on nitrogen and phosphorus excretion in swine waste. Applied Engineering in Agriculture 11(5):731–739. Carter, S. D., G. L. Cromwell, M. D. Lindemann, L. W. Turner, and T. C. Bridges. 1996. Reducing N and P excretion by dietary manipulation in growing and finishing pigs. J. Anim. Sci. 74(Suppl. 1):59 (Abstr.). Combs, N. R., E. T. Kornegay, M. D. Lindemann, and D. R. Notter. 1991. Calcium and phosphorus requirement of swine from weaning to market weight: 1. Development of response curves for performance. J. Anim. Sci. 69:673–681. Crenshaw, T. D., and J. C. Johanson. 1995. Nutritional strategies for waste reduction management: Minerals. Pp. 69–78 in New Horizons In Animal Nutrition and Health; J. B. Longenecker and J. W. Spears, eds. The Institute of Nutrition of The University of North Carolina, Chapel Hill, Nov. 7 and 8. Cromwell, G. L. 1989a. Requirements, biological availability of calcium, phosphorus for swine evaluated. Feedstuffs 60(23):16. Cromwell, G. L. 1989b. Requirements and biological availability of phosphorus for swine. Pp. 75–95 in Proc. Pitman-Moore Nutr. Conf., Des Moines, IA. Cromwell, G. L., and R. D. Coffey. 1991. Phosphorus–a key essential nutrient, yet a possible major pollutant–its central role in animal nutrition. Pp. 133–145 in Biotechnology in the Feed Industry, T. P. Lyons, ed. Nicholasville, KY: Alltech Technical Publications. Cromwell, G. L., T. S. Stahly, R. D. Coffey, H. J. Monegue, and J. H. Randolph. 1993. Efficacy of phytase in improving the bioavailability of phosphorus in soybean meal and corn–soybean meal diets for pigs. J. Anim. Sci. 71:1831–1840. Gahl, M. J., T. D. Crenshaw, and N. J. Benevenga. 1995. Diminishing returns in weight, nitrogen, and lysine gain of pigs fed six levels of lysine from three supplemental sources. J. Anim. Sci. 72:3177–3187. Hacker, R. R., and Z. Du. 1993. Livestock pollution and politics. Pp. 3–21 in Nitrogen flow in pig production and environmental consequences; M. W. A. Verstegen, L. A. den Hartog, G. J. M. van Kempen and C. J. H. M. Metz, eds. EAAP publ. 69, Pudoc Scientific Publishers, Wageningen. Hahn, J. D., and D. H. Baker. 1993. Growth and plasma zinc responses of young pigs fed pharmacologic levels of zinc. J. Anim. Sci. 71:3020–3024. Harper, A. F. 1994. Feeding technologies to reduce excess nutrients in swine diets. Pp. 44–51 in Proc. Meeting the Challenge of Environmental Management on Hog Farms. Second Annual Virginia Tech Swine Producers Seminar, Carson, Aug. 4.

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--> Heady, E. O., R. Woodworth, D. R. Catron, and G. C. Ashton. 1954. New procedures in estimating feed substitution rates and in determining economic efficiency in pork production. Agric. Exp. Sta. Res. Bull., pp. 893–976. Iowa State College, Ames. Henry, Y., and J. Y. Dourmad. 1992. Protein nutrition and N pollution. Feed Mix. (May), pp. 25–28. Hill, G. M., G. L. Cromwell, T. D. Crenshaw, R. C. Ewan, D. A. Knabe, A. J. Lewis, D. C. Mahan, G. C. Shurson, L. L. Southern, and T. L. Veum. 1996. Impact of pharmacological intakes of zinc and (or) copper on performance of weanling pigs. J. Anim. Sci. 74(Suppl. 1):181 (Abstr.). Jongbloed, A. W., Z. Mroz, and P. A. Kemme. 1992. The effect of supplementary Aspergillus niger phytase in diets for pigs on concentration and apparent digestibility of dry matter, total phosphorus, and phytic acid in different sections of the alimentary tract. J. Anim. Sci. 70:1159–1168. Kemme, P. A., A. W. Jongbloed, Z. Morz, and M. Mäkinen. 1995. Apparent ileal amino acid digestibility in pigs as affected by phytate, microbial phytase, and lactic acid. J. Anim. Sci. 73(Suppl. 1):173 (Abstr.). Kerr, B. J., and R. A. Easter. 1995. Effect of feeding reduced protein, amino acid supplemented diets on nitrogen and energy balance in grower pigs. J. Anim. Sci. 73:3000–3008. Kornegay, E. T. 1978a. Feeding value and digestibility of soybean hulls for swine. J. Anim. Sci. 47:1272–1280. Kornegay, E. T. 1978b. Protein digestibility of hydrolyzed hog hair meal for swine. Anim. Feed Sci. Technol. 3:323–328. Kornegay, E. T. 1996. Nutritional, environmental and economical considerations for using phytase in pig diets. Pp. 279–304 in Nutrient Management of Food Animals to Enhance and Protect the Environment, E. T. Kornegay, ed. Boca Raton, FL: CRC Press Inc. Kornegay, E. T., and A. F. Harper. 1997. Environmental nutrition: Nutrient management strategies to reduce nutrient excretion of swine. The Professional Animal Scientist 13:99–111. LeMieux, F. M., L. V. Ellison, T. L. Ward, L. L. Southern, and T. D. Bidner. 1995. Excess dietary zinc for pigs weaned at 28 days. J. Anim. Sci. 74(Suppl. 1):72 (Abstr.). Lei, X. G., P.. Ku, E. R. Miller, D. E. Ullrey, and M. T. Yokoyama. 1993. Supplemental microbial phytase improves bioavailability of dietary zinc to weanling pigs. J. Nutr. 123:1117–1123. Lei, X. G., P. K. Ku, E. R. Miller, M. T. Yokoyama, and D. E. Ullrey. 1994. Calcium level affects the efficacy of supplemental microbial phytase in corn–soybean meal diets of weanling pigs. J. Anim. Sci. 72:139–143. Mroz, Z., A. W. Jongbloed, and P. A. Kemme. 1994. Apparent digestibility and retention of nutrients bound to phytate complexes as influenced by microbial phytase and feeding regimen in pigs. J. Anim. Sci. 72:126–132. Mueller, J. P., J. P. Zublena, M. H. Poore, J. C. Barker, and J. T. Green. 1994. Managing pasture and hay fields receiving nutrients for anaerobic swine waste lagoons. N.C. Cooperative Ext. Service, AG-506. National Research Council. 1988. Nutrient Requirements of Swine. National Research Council, 9th revised ed. Washington, DC: National Academy Press. 93 pp. Pallauf, J., G. Rimbach, S. Pippig, B. Schindler, and E. Most. 1994. Effect of phytase supplementation to a phytate-rich diet based on wheat, barley and soya on the bioavailability of dietary phosphorus, calcium, magnesium, zinc and protein in piglets. Agribiol. Res. 47:39–48. Pierzynski, G. M., J. T. Sims, and G. F. Vance. 1994. Soils and Environmental Quality. Boca Raton, FL: Lewis Publishers, CRC Press. 313 pp. Radcliffe, J. S., E. T. Kornegay, and D. E. Conner, Jr. 1995. The effect of phytase on calcium release in weanling pigs fed corn–soybean meal diets. J. Anim. Sci. 73(Suppl. 1):173 (Abstr.). Sharpley, A. N., S. C. Chapra, R. Wedepohl, J. T. Sims, T. C. Daniel, and K. R. Reddy. 1994. Managing agricultural phosphorus for protection of surface waters: Issues and options. J. Environ. Qual. 23:437–451. Smith, II, J. W., M. D. Tokach, R. D. Goodband, J. L. Nelssen, W. B. Nessmith, Jr., K. Q. Owen, and B. T. Richert. 1995. The effect of increasing zinc oxide supplementation on starter pig growth performance. J. Anim. Sci. 73(Suppl. 1):72 (Abstr.). Spears, J. W. 1996. Optimizing mineral levels and sources for farm animals. Pp. 259–276 in Nutrient Management of Food Animals to Enhance and Protect the Environment, E. T. Kornegay, ed. Boca Raton, FL: CRC Press, Inc.

Representative terms from entire chapter:

microbial phytase