Nutritional strategies to reduce environmental emissions from nonruminants

The amount of nutrients (i.e., N, P, Zn, and Cu) and associated odors emitted from production animals into the environment can be modulated by several different nutritional strategies, but their practical application is dependent on costs and biological limitations. In general, nutrient excretion may be reduced by avoiding the overfeeding of specific nutrients or by using nutritional manipulations to enhance nutrient utilization in the animal. Loss to the environment can be avoided by manufacturing and handling the feed in a pelletized form that will minimize waste and improve feed/gain. Other strategies for minimizing nutrient losses include: 1) the development of feeding programs that are specific for sex and strain of the animal; 2) increasing the number of feed phases to better meet the animal's age-related requirements; 3) formulating diets to include the minimal amounts of nutrients required to satisfy production goals; 4) meeting the animal's amino acid requirements; 5) using synthetic amino acid supplements to feed to reduce N emission; 6) using feed ingredients with high digestibility and nutrient bioavailability; and 7) formulating diets based on nutrient availability instead of total nutrient content. Nutrient digestibility of feedstuffs is dependent on processing conditions, genetic characteristics of the grains and oilseeds, and the presence of nutritional antagonists in specific feedstuffs used in the diet. Feed ingredients that lead to odor production can be avoided (e.g., fishmeal and some easily fermentable feed ingredients). Feed additives, such as antibiotics, nonstarch polysaccharides, direct-fed microbials, organic acids, microbial enzymes (i.e., phytase, carbohydrases, and proteases) can be used to increase the digestibility and absorption of nutrients or to modulate the microflora. Finally, a cost factor for the control or disposal of nutrients or odor should be considered in the feed formulation to optimize the various nutritional strategies discussed above. Regardless of biological and economic limitations, significant reductions in nutrient and odor emission from nonruminants can be achieved by appropriate nutritional strategies, but response may differ for swine and poultry.