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

Sulfur is an essential nutrient for animal growth but is also associated with odor and morbidity of animals from swine operations. A study was conducted to determine the effects of increasing dietary S levels in swine diets on DM, pH, C, N, S, VFA, indole, and phenol concentrations in the manure, and on the emissions of C-, N-, and S-containing gases. A total of 24 gilts averaging 152 kg BW were fed diets containing 0.19, 0.30, 0.43, or 0.64% dietary S, as supplied by CaSO₄, for 31 d, with an ADFI of 3.034 kg d^-1. Feces and urine were collected after each feeding and added to manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary S lowered manure pH by 0.3 units and increased DM, N, and S by 10% for each 1.0 g S increase kg^-1 feed intake. Increased dietary S increased NH₃, sulfide, butanoic, and pentanoic acid concentrations in manure. Carbon and N emissions were not significantly impacted by dietary S, but S emissions in the form of hydrogen sulfide (H₂S) increased by 8% for each 1.0 g S increase kg^-1 feed intake. Odor increased by 2% for each 1.0 g increase of S consumed kg^-1 feed intake. Phenolic compounds and H₂S were the major odorants emitted from manure that increased with increasing dietary S.