Impact of distillers grain solids (Dgs) and seasonality on the prevalence of escherichia coli o157 at an abattoir in the u. s. upper midwest

Enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7 is carried asymptomatically by cattle gastrointestinal tract and the inclusion of distillers grains solids (DGS) in feed is thought to be a factor in the prevalence and persistence of EHEC O157 in a herd. The present study surveys the faecal prevalence of E. coli O157 in cattle processed at an abattoir in the Upper Midwest and its association with environmental factors and feeding practices. Faecal samples were collected from pre-processing cows during a 1-year period. E. coli O157 prevalence was estimated isolation of putative positives and confirmation of isolates by immunoassay and multiplex virulence genes PCR analysis. Overall, E. coli O157 was confirmed in 11.2% of samples. Prevalence during winter was the highest at 14% followed by summer (11.6%) and declined to less than 8% the rest of the year. Winter was the only season that had a statistically significant effect on prevalence. As a category unto itself, DGS feeding before arrival had no significant influence on faecal prevalence. However, we found a significant interaction of DGS feeding and summer. This observation is extremely relevant because it corroborates a previous study and suggests possible feeding practices to abate EHEC O157 presence during harvest.