Impact of Protein Level and Source on Manure and Air Emissions from Swine Diets

Improved utilization of CP in swine diets has the potential to lower emissions of gases and odorants from swine production. Two experiments were conducted to determine the effect of dietary CP level and source has on manure composition and gas emissions. In Experiment 1 two groups of 12 gilts averaging 96.13 kg BW were fed three CP levels through the replacement of soybean meal (CSBM) with crystalline AA (8.7% to 17.6% CP) with an ADFI of 2.74 kg/d over a 42 d trial. In Exp 2, two groups of 32 gilts averaging 99.09 kg BW were fed diets containing 17.6% CP as supplied by CSBM, corn gluten meal (CGM), Canola meal (CM), or poultry meal (PM) with an ADFI of 2.73 kg/d over a 42 d trial. In each experiment, feces and urine were collected after each feeding and added to manure storage containers. At the end of each experiment, stored manures were monitored for gas emissions and chemical properties. In Exp. 1, regression analysis was used to determine the effects of CP levels in the diet. CP levels in the diet increased manure pH by 0.15 units, and decreased NH3, VFA, and phenols by 7.4%, 5.4%, and 6.2%, respectively, for each % of CP reduced in the diet. Emissions of NH3, H2S, and odor were reduced by 9.4%, 4.3%, 6.3%, respectively for each % reduction in CP content in the diet. In Exp. 2, ANOVA indicated that CP source had a significant effect on excretion of DM, C, N, S in manure. Animals fed CM diet had significantly higher levels of C, N, and S in manure compared to animals fed CSBM diets. In conclusion, dietary CP levels and the source of CP have a dramatic impact on manure composition and gas emissions.