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United States Department of Agriculture

Agricultural Research Service

Title: How Diet Formulations Affect Nutrient Excretion

Author
item Cole, Noel

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 29, 2003
Publication Date: September 8, 2003
Citation: Cole, N.A. 2003. How diet formulations affect nutrient excretion. Proceedings of the Annual American Feed Manufacturers Liquid Feed Symposium. p. 11-28.

Interpretive Summary: The feeding of livestock in confinement leads to concentration of feed nutrients such as nitrogen (N), phosphorus (P), and trace minerals into a relatively small geographic area. Cattle excrete approximately 70 to 90% of the N and P they consume; thus, only a small percentage of the nutrients consumed are ultimately retained by the animal and removed when the animal leaves the facility. The accumulation of these 'excess' nutrients, the extraneous losses of these nutrients to ground water, surface water, and the atmosphere, and removal of accumulated manure has become a significant environmental concern to the livestock industries. Regulations now require all confined animal feeding operations (CAFOs) to have a Comprehensive Nutrient Management Plan to 'minimize impact on water quality and public health.' This manuscript reviews possible dietary methods that can be used to decrease nitrogen and phosphorus losses from cattle feeding and dairy operations. In general, the quantity of manure produced can be decreased by reducing the roughage concentration of the diet and(or) by properly processing the grain portion of the diet. Nitrogen losses can be decreased by several methods: 1) optimizing the amount of metabolizable protein fed, 2) optimizing the amino acid supply in the lower gut, 3) increasing digestion of dietary protein, 4) altering the site of digestion of dietary protein, 5) maximizing ruminal microbial protein synthesis, and 6) increasing N recycling between segments of the gut. Phosphorus losses can be decreased by using less supplemental phosphorus and by using more available forms of phosphorus in supplements.

Technical Abstract: The feeding of livestock in confinement leads to concentration of feed nutrients such as nitrogen (N), phosphorus (P), and trace minerals into a relatively small geographic area. Cattle excrete approximately 70 to 90% of the N and P they consume; thus, only a small percentage of the nutrients consumed are ultimately retained by the animal and removed when the animal leaves the facility. The accumulation of these 'excess' nutrients, the extraneous losses of these nutrients to ground water, surface water, and the atmosphere, and removal of accumulated manure has become a significant environmental concern to the livestock industries. Regulations now require all confined animal feeding operations (CAFOs) to have a Comprehensive Nutrient Management Plan to 'minimize impact on water quality and public health.' This manuscript reviews possible dietary methods that can be used to decrease nitrogen and phosphorus losses from cattle feeding and dairy operations. In general, the quantity of manure produced can be decreased by reducing the roughage concentration of the diet and(or) by properly processing the grain portion of the diet. Nitrogen losses can be decreased by several methods: 1) optimizing the amount of metabolizable protein fed, 2) optimizing the amino acid supply in the lower gut, 3) increasing digestion of dietary protein, 4) altering the site of digestion of dietary protein, 5) maximizing ruminal microbial protein synthesis, and 6) increasing N recycling between segments of the gut. Phosphorus losses can be decreased by using less supplemental phosphorus and by using more available forms of phosphorus in supplements.

Last Modified: 9/2/2014
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