Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 25, 2012
Publication Date: November 20, 2012
Citation: Hales, K.E., Cole, N.A., Varel, V.H. 2012. Effects of corn processing method and dietary inclusion of corn wet distillers grains with solubles on odor and gas production in cattle manure. Journal of Animal Science. 90:3988-4000. Interpretive Summary: Animal production has long been considered a source of odor. The growing ethanol industry has recently increased the use of wet distillers grains with solubles (WDGS) in beef cattle finishing diets. Two experiments were conducted to evaluate odorous compound production in urine and feces of feedlot steers fed diets with different concentrations of WDGS and different grain processing methods. Our findings show that manure from cattle fed a dry-rolled corn diet had greater initial total volatile fatty acid (VFA) concentration than manure from cattle fed steam-flaked corn and accumulated a greater concentration of total gas. Furthermore, dry-rolled corn-based manure produced more hydrogen and total gas production; whereas, steam-flaked corn-based manure resulted in more methane production. Additionally, total VFA concentrations were similar across all steam-flaked corn manures initially and on day 28; however throughout the incubation, manure with the lowest WDGS concentration had the greatest total VFA concentration.
Technical Abstract: The growing ethanol industry in the Southern Great Plains has recently increased the use of wet distillers grains with solubles (WDGS) in beef cattle finishing diets. Two experiments were conducted to evaluate odorous compound production in urine and feces of feedlot steers fed diets with different concentrations of WDGS and different grain processing methods. In both experiments a Latin square design was used. In Exp. 1 a 2 x 2 factorial arrangement of treatments was used and the factors consisted of corn processing method (steam-flaked corn [SFC] or dry-rolled corn [DRC]) and inclusion of corn-based WDGS (0 or 30% on a DM basis). Thus, the 4 treatment combinations consisted of: (1) SFC-based diet with 0% WDGS (SFC-0); (2) SFC-based diet with 30% WDGS (SFC-30); (3) DRC-based diet with 0% WDGS (DRC-0); and (4) DRC-based diet with 30% WDGS (DRC-30). In Exp. 2, all diets were based on SFC and the 4 treatments consisted of: (1) 0% WDGS (SFC-0); (2) 15% WDGS (SFC-15); (3) 30% WDGS (SFC-30); (4) 45% WDGS (SFC-45). In both experiments, diets were balanced for degradable intake protein and ether extract by the addition of cottonseed meal and fat. Fecal slurries were prepared from a 5 d composite of urine and feces collected from each treatment. The slurries were analyzed using a gas chromatograph for VFA, phenol, p-cresol, indole, skatole, hydrogen, methane, and total gas production. In Exp. 1, the DRC fecal slurries had greater initial total VFA concentration compared with the SFC-based slurries and accumulated a greater concentration of total gas throughout the incubation. Furthermore, DRC-based manure produced more hydrogen and total gas production, whereas, SFC-based manure resulted in more CH4 production. In Exp. 2, total VFA concentrations did not differ across all fecal slurries initially and on d 28; however, throughout the incubation SFC-0 and SFC-15 slurries had the greatest total VFA concentration.