Potential odorous volatile organic compound emissions from feces and urine from cattle fed corn-based diets with wet distillers grains and solubles

Abstract

Odor and volatile organic compound (VOC) emissions are a concern at animal feeding operations (AFOs). The issue has become more prevalent as human residences move into areas once occupied only by agriculture. Odors near AFOs are generally caused by odorous VOCs emitted from manure, the mixture of feces and urine. Wet distillers grains with solubles (WDGS) are a by-product of the ethanol industry, and WDGS have become a staple in many beef cattle finishing diets. The objective of this research was to determine specific VOC emissions from frozen feces and urine of cattle fed steam-flaked corn (SFC)-based diets containing 0, 15, 30, or 45% WDGS. No differences in flux were detected across dietary treatments for phenol, indole, skatole, or 4-methylphenol (P > 0.23). Dimethyl disulfide and dimethyl trisulfide flux in feces were not different across treatments (P > 0.35) and the flux of volatile fatty acids (VFA) such as acetic, propionic, isobutyric, butyric, isovaleric, and valeric were not different across treatments (P > 0.25). There was a tendency for dimethyl disulfide flux from urine to be greater for cattle consuming an SFC-based diet with 15% WDGS than the other diets (P = 0.10). Furthermore, flux of acetic, propionic, isobutyric, butyric, and isovaleric acid from the urine were not different (P > 0.61) across dietary treatment. There were no significant differences in odor activity value (OAV) across treatments for feces, and only a tendency for dimethyl disulfide in the feces (P = 0.09). Thus, there was no obvious indication that feeding WDGS in conjunction with SFC affects flux of odor or odorous VOC from beef manure. The summed OAV was three times higher in the urine than feces, and a single odorous compound (4-methylphenol) accounted for 97.6%and 67.3% of the OAV in urine and feces, respectively. Therefore, engineering or dietary strategies to reduce odor from beef cattle manure should focus on controlling or reducing 4-methylphenol concentrations in the urine and feces.