Nutrition and feed management can have a significant impact on the amount and concentration of nutrients excreted in hog manure, according to University of Missouri researchers.

Researchers say the combination of current technology and on-farm capabilities of feed delivery systems can help reduce nutrient excretion from 5% to 20% with little added production cost.

Researchers looked at three strategies to reduce nitrogen excretion.

1. Establish more precise diet formulations. Management strategies and a better understanding of genetic-specific nutrient requirements (based on lean growth) will decrease the quantity of excreta and the quantity of nitrogen it contains. The reduction is a combination of reduced input and more efficient use of nutrients.

The greatest management opportunity for reducing nitrogen output lies in phase feeding and split-sex feeding of the ideal amino acid ratio.

With phase feeding, producers can provide several diets that are closely matched to the pigs' requirements at various stages of growth and reduce nitrogen excretion by 20-30%.

2. Reduce dietary protein concentrations. Reductions in crude protein can decrease pig performance. Research has shown that a low protein/amino acid deficient diet resulted in a reduction in feed intake, lower daily gain and poor carcass quality. But researchers have found a way to alleviate the depression in performance by supplementing synthetic amino acid to lower crude protein concentrations of the diets. Amino acid manipulation (crude protein lowered by 4%) can decrease nitrogen excretion by up to 40%.

3. Formulate diets using ileal amino acid digestibility values. Feedstuffs vary in digestibility of amino acids, therefore, ileal digestibilities provide a requirement that more closely meets the pig's requirement.

Researchers also looked at two strategies to reduce phosphorus excretions.

1. Formulate on an available phosphorus basis. In an effect to reduce nutrient excretion, the industry has moved towards expressing phosphorus requirements on an "available phosphorus" basis, rather than total phosphorus. Therefore less phosphorus supplementation is needed and the phosphorus content is reduced.

2. Adding dietary phytase. The addition of dietary phytase improves the digestibility of phosphorus and decreases phosphorus excretion by 30% to 60%. Phytase allows lower inclusion levels of phosphates and limestone because phytase also enhances the digestibility of energy, protein, amino acid, nitrogen and other minerals such as calcium in the diet.