Nutrition affects odor emission from pig manure

Abstract

Odor from pig manure can create serious nuisance for people living near pig farms. Odor is a mixture of various compounds, of which 4 groups may be the major contributors: sulfurous compounds, indolic and phenolic compounds, volatile fatty acids, and ammonia and volatile amines. Odor mainly originates from microbial conversion of protein (CP) and fermentable carbohydrates (FC) in the large intestine of pigs and by microbial conversion of urinary and fecal compounds in the manure. There is increasing interest in reducing odor at the source by altering the diet. In four different experiments, dietary factors were investigated for effects on odor (measured by olfactometry) and ammonia emission from growing and finishing pigs manure. Lowering dietary CP level from 18 to 12% and supplementing essential amino acids (AA) reduced odor emission by 77%. Supplementing sulfur-containing AA at a level of three times the animal requirement increased odor emission by 823%.. At a high dietary CP level, increased FC levels decreased odor emissions, while at a low CP level, increased FC levels increased odor emission from pig manure. Ammonia emission from pig manure was reduced by lowering dietary CP level and supplementing most essential AA and by increasing dietary FC. The correlation between odor emission and ammonia emission was low and non-significant. From our studies we conclude that sulfurous compounds are the most important odorous compounds causing odor nuisance.