Evaluation of feeding dried distiller's grains with solubles and dry-rolled corn on the fecal prevalence of Escherichia coli O157:H7 and Salmonella spp. in cattle.

Escherichia coli O157:H7 and Salmonella are foodborne pathogens that reside in the gut of cattle and are shed in the feces. Previous work indicated a positive association between feeding cattle distiller's grains (DG) and an increase in E. coli O157:H7 prevalence. Feeding processed grains also has been shown to affect fecal prevalence of E. coli O157:H7. The objective of this study was to evaluate the effect of feeding DG and dry-rolled corn (DRC), alone or in combination, on fecal prevalence of E. coli O157:H7 and Salmonella in finishing cattle. Cattle were allotted to pens (n = 28), and fed dietary treatments (n = 150 days) structured in a 2 x 2 factorial arrangement; the factors were 0% or 25% dried corn DG with solubles (DDGS) and 0% or 25% DRC in steam-flaked corn-based high-grain diets. Fecal samples were collected from each pen floor before initiating dietary treatments and at least once every 2 weeks after final diets began. Overall prevalence of E. coli O157:H7 in fecal samples was 5.1%. There were no significant effects of DDGS, DRC, or sampling time on E. coli O157:H7 prevalence (p > 0.20). Overall prevalence of Salmonella in pen floor fecal samples was 23.7%, and sampling week affected prevalence (p < 0.01), ranging from < 1% (week 1) to 77.5% (week 17). Salmonella prevalence was not affected by cattle diet, and no work had previously reported an association between either DG or DRC and Salmonella prevalence. Lack of an association between E. coli O157:H7 prevalence and feeding DG or DRC is contrary to previous observations. Further research is needed to understand inconsistencies between studies of E. coli O157:H7 prevalence and potential associations with DG and grain-processing methods.