Potential for reduction of odorous compounds in swine manure through diet modification

Recent public concern about air pollution from pork production units has pr ompted more research to develop methods to reduce and control odors. Maskin g agents, enzymes and bacterial preparations, feed additives, chemicals, ox idation processes, air scrubbers, biofilters, and new ventilation systems h ave been studied. Research relating the effects of the swine diet on manure odors has been scarce. Introducing feed additives to bind ammonia, change digesta pH, affect specific enzyme activity, and mask odors has been either costly or not consistently successful. Recent research emphasis-has focuse d on manipulating the diet 1) to increase the nutrient utilization of the d iet to reduce excretion products, 2) to enhance microbial metabolism in the lower digestive tract to reduce excretion of odor-causing compounds, and 3 ) to change the physical characteristics of urine and feces to reduce odor emissions. Primary odor-causing compounds evolve from excess degradable pro teins and lack of specific fermentable carbohydrates during microbial ferme ntation. Reductions in ammonia emissions by 28 to 79% through diet modifica tions have been reported. Limited research on reduction of other odorous vo latile organic compounds through diet modifications is promising. Use of sy nthetic amino acids with reduced intact protein levels in diets significant ly reduces nitrogen excretions and odor production. Addition of nonstarch p olysaccharides and specific oligosaccharides further alters the pathway of nitrogen excretion and reduces odor emission. Continued nutritional and mic robial research to incorporate protein degradation products, especially sul fur-containing organics, with fermentable carbohydrates in the lower gastro intestinal tract of pigs will further control odors from manure.