Swine diets impact manure characteristics and gas emissions: Part II protein source

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: 11/23/2020
Publication Date: 4/1/2021
Citation: Trabue, S.L., Kerr, B.J., Scoggin, K.D., Andersen, D., Van Weelden, M. 2021. Swine diets impact manure characteristics and gas emissions: Part II protein source. Science of the Total Environment. 763. Article 144207. https://doi.org/10.1016/j.scitotenv.2020.144207.
DOI: https://doi.org/10.1016/j.scitotenv.2020.144207

Interpretive Summary: Soybean meal is the most common protein source for swine diets in the United States driven largely by economics, but economics conditions change requiring growers to consider cheaper alternatives. Three alternative protein sources were compared to soybean meal and included: corn gluten meal (grain co-product); canola meal (plant based protein); and poultry meal (animal co-product). Animals fed alternative protein grew just as well as animals fed soybean meal diets, but animals fed alternative protein diets did not retain nutrients as well as animals fed soybean meal. Manure of animals fed alternative protein tended to have higher levels of solids, carbon, protein, and sulfur than animals fed soybean meal, but this did not necessarily increase emissions from these manures nor did it increase odor emissions. Animals fed canola meal diets had higher levels of odorous compounds including sulfides and volatile fatty acids compared to animals fed soybean meal diets. Emissions of ammonia from manure was reduced by feeding canola meal to animals compared to soybean meal and this was due to the lower manure pH. There were no increases in odor emissions from animals fed alternative protein diets compared to animals fed soybean meal diets. Information from this research will be of value to researchers and growers looking for alternative feed ingredients to reduce diet cost or understand environmental impact of animal diet sources.

Technical Abstract: Soybean meal is the most common protein source for swine diets in the United States driven largely by economics, but economics conditions change requiring growers to consider cheaper alternatives. A feeding trial was conducted to determine the effect of dietary protein source material on manure slurry chemical properties and gas emissions. A total of 32 gilts averaging 130 kg BW were fed a control diet formulated with soybean meal (SB) or alternative protein source that included corn gluten meal (CG); canola meal (CM); or poultry meal (PM) all diets contained 176 g protein kg-1. Diets were fed for 42 d with an average daily feed intake of 2.68 kg/d. 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. Dietary protein source had a significant effect on manure pH and excretion of dry matter, C, protein, and S in manure. Pigs fed the diets containing CM had significantly higher levels of sulfide, butanoic acid, and branch chain fatty acids compared to pigs fed SB diets. Pigs fed CM diets had significantly lower emissions of NH3 compared to pigs fed SB diets. There were no significant differences in C or S emissions as affected by dietary treatment. There were no significant differences in odorant emission as affected by dietary treatment. Hydrogen sulfide emissions from manure was the most dominate odorant for all dietary treatments.