MANIPULATION OF ANIMAL DIETS TO AFFECT MANURE PRODUCTION, COMPOSITION AND ODORS: STATE OF THE SCIENCE

Abstract

Manure is composed of feces, bedding, wasted feed, and runoff water. Most of manure nutrientscome from urine and feces excreted from animals that contain undigested components from theirdiets, excretion end products from normal metabolism, and bacterial cells from indigenous bacteriain the digestive tract. The amount and composition of freshly excreted manure can vary and is primarilyinfluenced by the original composition of the diet. Diet ingredient sources, forms and levelscan influence nutrient availability, excretion levels and forms. Because ruminants (including beefcattle and dairy cattle in this paper) have different digestive systems compared to nonruminants (includingpoultry and swine in this paper) excreta volume and composition differs. The digestive tractof a ruminant includes a multi (4)-compartment stomach that possesses a microbial population capableof digesting and releasing nutrients from highly fibrous feeds (forages) or highly digestiblegrains for the animals use. The nonruminant has a simple stomach (one compartment) that does notefficiently digest highly fibrous feeds, but requires highly digestible grains readily digested by enzymesto release nutrients for the animals use. Understanding the bioavailability of nutrients fromfeed sources used in the diets is critical for formulating a diet that will meet the productive needs ofthe animal. Feed management practices can also influence the efficiency of nutrient utilization inlivestock and poultry operations. Odorous and gaseous compounds are emitted immediately afterexcretion due to microbial metabolism in the digestive tract of the animal. Further decompositionduring storage can occur resulting in gaseous emissions and odors that have an impact on air quality.Since the animal is the initial source of nutrient excretions and odors from animal operations,diet manipulation is a practical and economical way to control excess nutrient excretions and reducegaseous emissions. This paper summarizes key research approaches and results related to usingdiet manipulation to reduce nutrient excretions and minimize odors from livestock and poultryoperations. In addition, this paper identifies some information gaps and needed research to fill thevoids in information to maintain livestock and poultry production while sustaining environmentalstewardship.