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

Swine growers seeking to lower costs and environmental impact have turned to alternative carbohydrate feed sources. A feeding trial was conducted to determine the effect carbohydrate sources have on manure composition and gas emissions. A total of 48 gilts averaging 138 kg BW were fed diets consisting of (a) low fiber (LF) grain, or (b) high fiber (HF) aro-industrial co-product (AICP). The LF diets included corn and soybean meal (CSBM) and barley soybean meal (BSBM). The HF AICP diets were CSBM based and supplemented with one of the following materials: beet pulp; corn distillers dried grains with solubles; soybean hulls; or wheat bran. 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 and added to manure storage containers in which manure slurries were monitored for gas emissions and chemical properties. Manures of animals fed HF diets had significantly (P < 0.05) more excretion of solids, C, N, and organic N, but less total S compared to pigs fed the LF diets. Animals feed HF diets had significantly (P < 0.05) higher levels of ammonia, sulfide, volatile fatty acids, and phenols in manure compared to pigs fed the LF diets. Manure of animals fed HF diets had 30% (P < 0.05) lower NH3 and 17% lower hydrogen sulfide emissions; however, fiber had no impact on odor emissions. Based on the partitioning of nutrients, animals fed HF fiber diets had increased manure retention for C and N but decreased levels of N gas emissions and manure S. There were little differences in manure and gas emissions for animals fed LF diets, but the source of HF AICP diets had a significant impact on manure composition and gas emissions.

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

Soybean meal is the dominate protein source for swine diets in the world driven largely by economics, nutritive value, and availability; but conditions can change requiring growers to consider more economical and available protein alternatives. A feeding trial was conducted to determine the impact dietary protein source material on manure slurry chemical properties and manure gas emissions. A total of 32 gilts averaging 130 kg BW were fed either a control diet formulated with soybean meal (SB) or an alternative protein source that included corn gluten meal (CG); canola meal (CM); or poultry meal (PM), with all diets containing 176 g protein kg^-1. Diets were fed for 45 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 animal-specific 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 (P < 0.05) on manure pH, total solids, total C, protein N, and total S. 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 (P < 0.05). Pigs fed CM diets had significantly lower emissions of NH₃ compared to pigs fed SB diets (P < 0.05). There were no significant differences in C or S emissions or in odorant emission as affected by source of dietary protein. Hydrogen sulfide was the most dominate odorants for all dietary treatments.

Swine diets impact manure characteristics and gas emissions: Part I protein level

Crude protein (CP) is a key nutrient in swine diets supplying essential amino acids, N, and S to animals for growth are fed in excess to maximize growth. Swine diets reduced in CP and supplemented with crystalline amino acids have been shown effective at maintaining animal growth while increasing overall CP use efficiency. A feeding trial study was conducted to determine the effects of reduced dietary CP levels on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 111 kg BW were fed corn and soybean meal diets formulated with 8.7, 14.8, and 17.6% CP using crystalline amino acid supplementation in the 8.7 and 14.8% CP diets, but only intact protein, soybean meal, in the diet containing 17.6% CP. Diets were fed for 45 d with an average daily feed intake (ADFI) of 2.70 kg across all diets. Animals were fed twice daily with both feces and urine collected during each feeding and added to animal-specific manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary CP levels increased manure pH, total solids, total N, and total S, including increased levels of ammonia (NH₃), volatile fatty acids, and phenolic compounds. Pigs fed lower CP diets had lower emissions of NH₃, branched chain fatty acids (BCFA), and phenol compounds which translated into lower emissions in total odor. Emissions of NH₃ and odor were reduced by 8.9% and 4.2%, respectively, for each unit percent decline in dietary CP. Hydrogen sulfide was the dominate odorant associated with manure odor emissions. Based on nutrient mass balance, animal retention of dietary N and S increased by 7.0% and 2.4%, respectively, for each unit percent drop in crude protein fed animals, while C retention in the animal declined by 2.1%.