A randomized controlled trial to evaluate the effects of dietary fibre from distillers grains on enterohemorrhagic Escherichia coli detection from the rectoanal mucosa and hides of feedlot steers.

Feeding high levels (≥40% dry matter) of distillers grains may increase the risk for cattle to carry enterohemorrhagic Escherichia coli (EHEC) O157. The mechanism for the increased risk is not known nor whether non-O157 EHEC are similarly affected. Our objective was to test whether the fibre content or other components of modified distillers grains plus solubles (MDGS) affects the probability for cattle to carry EHEC serogroups of public health importance. A 2 × 2 plus 1 factorial treatment arrangement within a randomized block design was utilized. Within each of four blocks, 25 feedlot pens (n = 8 steers/pen) were assigned randomly to (i) corn-based control diet; (ii) 20% dry matter (DM) MDGS; (iii) 40% DM MDGS; (iv) corn bran added to corn-based diet to match fibre of 20% MDGS or (v) 40% MDGS. Rectoanal mucosa swabs (RAMS) were collected on day (d)0, d35, d70 and d105; hide swabs were collected on the last feeding day. Samples were tested for EHEC by a molecular screening assay. The effects of fibre source and fibre level on EHEC carriage were tested using multilevel logistic regression (generalized linear mixed models; α = 0.05). EHEC O45 RAMS detection was associated with fibre level, source and sampling day. EHEC O103 RAMS detection increased by feeding 40% MDGS but not the corresponding corn bran diet. Hide contamination by EHEC O45 or O103 was less likely in cattle fed MDGS compared to corn bran diets. EHEC O111 RAMS detection decreased by feeding 40% MDGS but not by feeding the corresponding corn bran diet. Detection of EHEC O157 or O145 was not associated with dietary factors. Feeding 40% MDGS increased the probability for carriage of some EHEC serogroups but decreased probability of others, which indicated that EHEC serogroups have different risk factors associated with feeding MDGS and little association with dietary fibre.