Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/18/2008
Publication Date: 8/24/2009
Citation: Ziemer, C.J., Kerr, B.J., Trabue, S.L., Stein, H., Stahl, D.A., Davidson, S.K. 2009. Dietary Protein and Cellulose Effects on Chemical and Microbial Characteristics of Swine Feces and Stored Manure. Journal of Environmental Quality. 38(5):2138-2146. Interpretive Summary: Manure generation from livestock production facilities is valuable in providing nutrients back to soil following crop production, but does have negative effects such as odor emissions. For the value of manure to be achieved with minimal impacts to the environment, accurate information about its chemical and microbial composition is required. Two factors known to affect manure composition are the amount of nitrogen and fiber going into manure storage systems. The research conducted herein studied whether decreasing protein (nitrogen) and increasing soybean hulls (fiber) would change the the nutrient composition in manure and odors generated from stored pig manure. The most important factor in the chemical and microbial composition of manure was how much protein was fed, although adding soybean hulls to high-protein diets did reduce odorous compounds. The data also indicate that short-term manure collection (2 weeks) underestimated the odorous compounds in the manure relative to manure collected at week 8, such that it is recommended that future studies collect and hold manure for longer than 2 weeks. This data is important to both scientists and engineers providing information on the changing chemical and microbial composition of manure for use in future nutrition or manure processing research.
Technical Abstract: The objectives of this study were to investigate the effects of dietary crude protein (14.5 or 12.0%) and cellulose (8.7 or 2.5%) levels on chemical and microbial composition of feces and stored manure after 2 and 8 weeks of storage. Twenty-two pigs were fed twice daily with urine and feces collected after each feeding, subsequently being added to manure storage containers. On weeks 2 and 8 after initiation of the experiment, fresh fecal and manure samples were obtained for subsequent analysis. Increasing dietary cellulose had the greatest affects on chemical composition in feces at week 8, resulting in increased pH and volatile fatty acid and phenol concentrations. In contrast, dietary protein had the greatest affect on manure chemical composition, whereby lower protein decreased sulfur content and ammonia and phenolic compound concentrations. High levels of either dietary cellulose or protein tended to increase microbial community similarity in fecal samples, but only high protein increased similarity among manure sample microbial communities. Fecal and manure samples from week 2 were very different from samples taken in week 8 in both chemical and microbiological composition. Week 2 samples had lower concentrations of many of chemical compounds and microbial diversity than samples from week 8. In feces, results indicate that after 2 weeks of feeding experimental diets, animals were not fully adapted to the diets. More importantly, manure after 2 weeks of collection was not representative of stored manure (week 8), limiting its usefulness in developing standards and recommendations for on-farm management practices.