Effects of Dried Distiller's Grain on Cattle Fecal Prevalence and Growth of Escherichia coli O157 in Batch Culture Fermentations

Department of Diagnostic Medicine and Pathobiology, Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas 66506

^* To whom correspondence should be addressed. Email: tnagaraj{at}vet.k-state.edu.

	Abstract

Distiller's grains (DG), a byproduct of ethanol production, are fed to cattle. Associations between Escherichia coli O157 prevalence and feeding DG were investigated in feedlot cattle (n = 379) allocated to 1 of 3 diets: steam-flaked corn (SFC) and 15% corn silage with 0 or 25% dried DG (DDG); or SFC with 5% corn silage and 25% DDG. Ten fecal samples were collected from each pen weekly for 12 weeks to isolate E. coli O157. Cattle fed 25% DDG with 5 or 15% silage had a higher (P = 0.01) prevalence of E. coli O157 than cattle fed 0% DDG. Batch culture ruminal or fecal microbial fermentations were conducted to evaluate the effect of DDG on E. coli O157 growth. The first study utilized microbial inocula from steers fed SFC or dry-rolled corn with 0 or 25% DDG, and included their diet as substrate. Ruminal microbial fermentations from steers fed DDG had higher E. coli O157 growth than no DDG (P < 0.05) when no substrate was included. Fecal fermentations showed no DDG effect on E. coli O157 growth. In the second study with DDG as a substrate, ruminal fermentations with 0.5 g had higher (P < 0.01) E. coli O157 concentrations at 24 h compared to 0, 1, or 2 g DDG. In fecal fermentations, 2 g DDG resulted in a higher concentration (P < 0.05) at 24 h compared to 0, 0.5, or 1 g DDG. Results indicate a positive association between DDG and E. coli O157 in cattle, and the findings will have important ramifications for food safety.