This paper discusses general strategies to reduce nutrient excretion and describes specific methods to reduce nitrogen, phosphorus and micro-mineral excretion. General nutritional strategies to reduce nutritional excretion include feed efficiency, feed wastage, matching nutrient requirements and feed manufacturing. Methods to reduce nitrogen excretion and ammonia emissions would include selecting ingredients with highly digestible amino acid content, and putting the swine on low protein diets. Methods to reduce phosphorus excretion are formulations of diets based on the available phosphorus content and selection of ingredients with high phosphorus availability as that can lead to a reduction in phosphorus excretion. Another method is increasing the digestibility of phosphorus by the use of phytase. A method to reduce the excretion of micro-minerals is eliminating high zinc and copper feeding in the nursery phase.
The most cost effective methods that appear to be relatively easy to implement are reducing feed wastage, separate sex and phase feeding, and formulating diets based on nutrient availability. The use of phytase, low-phytate corn and low-protein diets could reduce nitrogen and phosphorus excretions substantially, but are likely to add additional cost to the diet.

Strategy Employed Reduction in Nutrient Excretion

Pelleting 5% for N and P
Reducing Feed Waste 1.5% for all nutrients for ever 1% reduction
Matching Nutrient Requirements 6 to 15% for all nutrients
(phase or separate-sex feeding)
Formulation on availability 10% for N and P
Low-Protein Diets 9% for N for every 1% reduction in CP
Phytase 25 to 50% for P
Low-Phytate Corn 35 to 40% for P
Reducing Micro-Minerals Up to 50%