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Title: Manure odor potential and Escherichia coli concentrations in manure slurries of feedlot steers fed 40% corn wet distillers grains

Author
item Varel, Vincent
item Wells, James - Jim
item Berry, Elaine
item Miller, Daniel

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2010
Publication Date: 7/1/2010
Citation: Varel, V.H., Wells, J., Berry, E.D., Miller, D.N. 2010. Manure odor potential and Escherichia coli concentrations in manure slurries of feedlot steers fed 40% corn wet distillers grains. Journal of Environmental Quality. 39(4):1498-1506.

Interpretive Summary: A feeding study was conducted on soil-based feedlot floors with 603 crossbred cattle that were fed a diet with no corn wet distillers grains with solubles (WDGS) in the diet or with 40 percent WDGS in the diet. WDGS is a byproduct from the ethanol industry, in which starch is removed from corn, converted to ethanol, and the byproduct remaining is a three-fold concentrate of the original protein, minerals, and oil. This byproduct may exceed the dietary requirements of an animal when used as feed. These excess nutrients will be excreted in manure and may cause environmental pollution. The objectives of this study were to determine the effect of feeding 40 percent WDGS to finishing cattle on manure odorant compounds produced and persistence of E. coli in fresh manure and manure slurries stored from 0 to 28 days. The amount of minerals and nutrients in the manure that were converted to odor increased when 40 percent WDGS was fed. Similarly, E. coli persisted longer in 40 percent WDGS manure slurries in comparison to 0 percent WDGS manure slurries. These studies confirm the results from an earlier study that was conducted on cement-floors, which indicated greater odor and a greater longevity of coliform bacteria when WDGS is included in cattle diets. Cattle producers should be aware of these findings when making decisions as to the level of WDGS to be included in diets.

Technical Abstract: This study evaluated feeding 0 and 40% wet distillers grains with solubles (WDGS) diets to cattle and effects on feedlot manure collected from soil-based pens and incubated for 28 d. Steers (n = 603; 261 ± 32 kg) were fed in eight pens (15 x 150 m) of 75 to 77 steers per pen. Two experiments were conducted with WDGS; one in which the corn source fed with WDGS was high-moisture, and the second experiment in which WDGS was fed with dry-rolled corn. The objectives of this study were to compare odorants (volatile fatty acids-VFA, aromatic compounds, NH3, H2S) and persistence of Escherichia coli in feedlot manure slurries stored from 0 to 28 d. Manure collected from cattle fed 40% WDGS had lower (P < 0.05) total VFA, including acetate, propionate, and butyrate, all of which continued to be lower after 28 d. However, these slurries had greater concentrations (P < 0.05) of branched-chained VFA (isobutyrate and isovalerate), especially after d 14 of incubations. Similarly, cresol and skatole concentrations tended to be greater in slurries originating from 40% WDGS diets, and increased with incubation time. Indole was initially greater in the slurries from 40% WDGS diets; however, it was metabolized by microbes during incubation. Manure slurries from the 40% WDGS diets had greater quantities of H2S, NH3, and P (P < 0.05). Levels of E. coli in 0 and 40% WDGS manure slurries were similar when high-moisture corn was the corn source in the diets. However, when dry-rolled corn was used, E. coli persisted longer in 40% WDGS manure slurries in comparison to 0% WDGS. Results here support earlier studies that suggest feeding WDGS increases odor emissions, N loss, E. coli survival, and surface water contamination due to greater potential P run-off.