Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions

Authors: Trabue, Steven - Steve; Kerr, Brian; Scoggin, Kenwood; ANDERSEN, DANIEL - Iowa State University; VAN WEELDEN, MARK - Iowa State University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2022
Publication Date: 6/15/2022
Citation: Trabue, S.L., Kerr, B.J., Scoggin, K.D., Andersen, D., van Weelden, M. 2022. Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions. Science of the Total Environment. 825. Article e153911. https://doi.org/10.1016/j.scitotenv.2022.153911.
DOI: https://doi.org/10.1016/j.scitotenv.2022.153911

Interpretive Summary: Livestock producers seeking to reduce the impacts of corn crop rotations and corn costs have turned to alternative feed grains and cheaper feed ingredients called co-products, which are plant materials derived during food production from crops. The co-products used in our work included: 1) beet pulp (co-product derived from sugar processing of beets); 2) soy hulls (co-product derived from soybean oil extraction); 3) wheat bran (co-product of the dry milling of wheat); and 4) distillers dried grains with soluble materials (co-product from corn ethanol production). A feeding trial was conducted to look at the impacts of alternative diets on animal growth, manure chemical properties, and development of gases. Animals fed barley, an alternative feed grain, showed no difference in growth, manure composition, or gas profile compared to animals fed corn based diets. Animals fed the co-product diets tended to have higher levels of solids and nutrients in the manure than did animals fed corn or barley diets. The development of ammonia gas from manure was 33% lower for animals fed co-product diets compared to animals fed either corn or barley-based diets. There were no increases in odor from feeding alternative diets compared to corn diets. Information from this research will be of value to researchers and growers looking for alternative feed ingredients to reduce diet cost or understand the environmental impact of animal diet source material.

Technical Abstract: Livestock producers seeking to reduce their environmental footprint and costs have turned to alternative feed grain and cheaper feed ingredients rich in fiber. A feeding trial was conducted to determine the effects of alternative diets on manure slurry chemical properties and gas emissions in finishing pigs. A total of 48 gilts averaging 138 kg BW were fed a control diet formulated with corn and soybean meal, an alternative small grain diet formulated with barley and commercial soybean meal (CSBM), and CSBM diets supplemented with various fibrous co-products, including beet pulp, distillers dried grains with solubles, soybean hulls, and wheat bran. All diets contained 16.3 g crude protein kg-1 feed. Diets were fed for 42 d with an average daily feed intake of 2.71 kg d-1. Feces and urine were collected twice daily after each feeding and added to the manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Alternative cereal grains had no effect on manure chemical composition nor gas emissions from manure. Animals fed different fibrous materials had significant (P < 0.05) effects on the excretion of solids, C, N, and S in the manure. Pigs fed high fiber diets had significantly (P < 0.05) more excretion of solids, C, and N, but less excretion of S and lower manure pH compared to animals fed low fiber diets. Animals fed high fiber diets had significantly (P < 0.05) higher levels of NH3, volatile fatty acids, and phenols in manure than pigs fed the low fiber diets. High fiber diets reduced NH3 emissions significantly (P < 0.05) by over 33% compared to animals fed low fiber diets, but high fiber diets had no impact on odor emissions. Based on the partitioning of nutrients, animals fed high fiber diets had increased manure C and N levels but decreased levels of N gas emissions and manure S.