Location: Meat Safety & Quality Research
Title: Impact of reducing the level of wet distillers grains fed to cattle prior to harvest on prevalence and levels of Escherichia coli O157:H7 in feces and on hides Authors
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 27, 2011
Publication Date: October 20, 2011
Citation: Wells, J., Shackelford, S.D., Berry, E.D., Kalchayanand, N., Bosilevac, J.M., Wheeler, T.L. 2011. Impact of reducing the level of wet distillers grains fed to cattle prior to harvest on prevalence and levels of Escherichia coli O157:H7 in feces and on hides. Journal of Food Protection. 74(10):1611-1617. Interpretive Summary: Wet distillers grains with solubles (WDGS) are a by-product of ethanol production. WDGS is less expensive than corn and cattle fed WDGS perform well, thus, it has become a common component of cattle feed. Previous data have indicated that feeding high levels of WDGS to feedlot cattle can increase the levels of E. coli O157:H7 in their feces compared to corn diets. This study was conducted to determine if shifting from high levels (40 or 70%) to lower levels (0 or 15%) of WDGS in the feedlot finishing diet would reduce the levels and frequency of E. coli O157:H7. Results confirm the frequency and levels of E. coli O157:H7 in the feces were higher for cattle fed high levels of WDGS compared to cattle fed no WDGS. In animals fed 40 or 70% WDGS and switched to 0 or 15% WDGS, E. coli O157:H7 frequency and levels in feces were lower compared to animals continuously fed 40% WDGS. In cattle switched from high levels of WDGS to lower levels, E. coli O157:H7 levels and frequency in feces were similar to cattle continuously fed corn diets with 0% WDGS. The reduction in E. coli O157:H7 levels and frequency in feces required 56 days of feeding at the lower WDGS levels. Because feeding WDGS is more economical than corn, switching finishing cattle from high levels of WDGS in the diet to 15% at least 56 days prior to harvest may be a viable option for minimizing food safety risks while retaining the advantages of feeding WDGS.
Technical Abstract: Cattle fed finishing diets with wet distillers grains with solubles (WDGS) have been shown to increase Escherichia coli O157:H7 in the feces and on the hides. To determine if feeding a lower level of WDGS at the end of the feeding period reduces E. coli O157:H7 load at harvest, 608 heifers were sorted into 1 of 5 treatments, and fed 0, 40, or 70% WDGS (DM basis). For 3 of the treatments, WDGS was reduced midway through the study. Treatment 0W0W (positive control) was fed corn grain continuously, and 40W40W (negative control) was fed 40% WDGS continuously. Treatments 40W0W, 40W15W and 70W15W were fed either 40% or 70% WDGS for the first 56 days, and switched to 0% or 15% WDGS, respectively, for the last 56 days. Prior to the switch in diets, animals fed diets with 40 or 70% had the highest prevalence and percent enumerable fecal samples for E. coli O157:H7. After the dietary switch, animals fed 40W0W, 40W15W, and 70W15W diets had similar fecal prevalence and percent enumerable samples (33.4 and 6.3%, 31.0 and 9.7%, 34.9 and 8.4%, respectively) as animals fed 0W0W diets (10.2 and 3.2%, respectively; P > 0.05), whereas animals fed 40W40W had the highest fecal prevalence and percent enumerable samples (70.1 and 29.2%, respectively; P < 0.05). Similar relationships between the treatments were observed for hide samples. Time after dietary switch was important, as animals fed lower levels had significantly lower fecal prevalence and percent enumerable samples after 56 days, but not after 28 days. The study indicates that cattle can be switched to lower levels of dietary WDGS (15% or less) 56 days prior to harvest to significantly reduce E. coli O157:H7 in feces and on hides.