Efficient Feed Nutrient Utilization to Reduce Pollutants in Poultry and Swine Manure

High-density livestock facilities lead to a concentration of livestock wastes and subsequent leakage of pollutants into the environment, resulting in public concern about their effects. Nitrogen (N) and phosphorus (P) are the most harmful components of animal manure, but odor from the manure itself and the livestock facilities is also a problem. Improving the nutrient efficiency of the livestock helps to decrease excretion of these environmental contaminants. Pigs and chickens are the main animals used in studies to improve nutrient efficiency to reduce excretion of environmental contaminants. Addition of feed supplements and modifying feeding programs to improve nutrient efficiency can result in significant decreases in the N, P, odor, and dry matter (DM) weight of manure. Examples of these methods include the following. (1) The addition of synthetic amino acids and reducing protein contents resulted in N reductions of 10 to 27% in broilers, 18 to 35% in chicks and layers, 19 to 62% in pigs, and a 9 to 43% reduction in odor from pigs. (2) Enzyme supplementation resulted in a 12 to 15% reduction in DM weight of broiler manure. (3) Phytase supplementation resulted in P reductions of 25 to 35% in chickens and 25 to 60% in pigs. (4) The use of growth-promoting substances resulted in a 5 to 30% reduction in N and a 53 to 56% reduction in odor from pigs. (5) Formulating diets closer to requirements (diet modification) reduced N and P by 10 to 15% each in chickens and pigs, and odor by 28 to 79% in pigs. (6) Phase feeding reduced N and P excretion by chicken and pigs from 10 to 33% and 10 to 13% each, as well as odor in growing and finishing pigs by 49 to 79%. (7) Use of highly digestible raw materials in feed reduced N and P excretion by 5% in chickens and pigs. Certain feed manufacturing techniques (grinding feed grains and proper particle size, feed uniformity in rations, or expanding and pelleting) when done properly can significantly reduce N, P, and odor contents and DM weight of chicken and pig manure. Feed with proper grinding reduced 27% of N in finishing pigs and 22 to 23% reduction of N in piglet fed with pelleting, 60% reduction of NH3 emission fed with finely ground Zeolites in pig, and a 26% reduction of DM weight in finishing pigs fed with proper grinding were reported, but further research is needed in this area. Coordinating actual feed analytical results with production technique modifications is needed to reduce environmental contamination by animal manure, but specialists may need to be consulted for the successful implementation of these efforts.