449 Late-Breaking: Impact of Feeding a Propriety Yeast-Based Synbiotic Product on Fecal Shedding of Top-7 Shiga Toxin-Producing Escherichia Coli in Feedlot Cattle

Shiga toxin-producing E. coli (STEC) belonging to serogroups O26, O45, O111, O103, O121, O145, and O157, called ‘top-7’, are major foodborne pathogens. Cattle are a major reservoir, in which STEC colonize the hindgut and are shed in the feces, which is a major source of contamination of food. Our objective was to evaluate the impact of a proprietary yeast-based synbiotic product (prebiotic and probiotic; Alltech, Inc., Nicholasville, KY) on fecal shedding of top-7 STEC in feedlot cattle. Twenty existing pens, housing 40–112 steers per pen, with an estimated 60 to 90 days to slaughter, were randomly assigned to a control group or a treatment group that received 22 g of the synbiotic product per steer per day, as a top dress, in a finishing diet. Twenty pen-floor fecal samples were collected from each pen on days 0, 21, 42, and 54. Fecal samples were enriched and subjected to a multiplex PCR assay targeting serogroup-specific genes for the top-7 STEC and three major virulence genes, stx1 (Shiga toxin 1), stx2 (Shiga toxin 2), and eae (intimin). Bivariate descriptive statistics for the major serogroups and virulence genes were assessed prior to multivariable analysis using mixed effects logistic regression. The overall prevalence of the top-7 serogroups were 44.5% of O26, 41.3% of O157, 15.1% of O103, 13.7% of O45, 7.8% of O121, and 0.6% of O111. The overall prevalence of stx1, stx2, and eae were 43.9%, 70.8%, and 49%, respectively. E. coli O26, O157, and O45 had a significant treatment and sampling day interaction (P < 0.0001). On d 42, fecal samples from treated group had lower prevalence (P < 0.01) of O26, O103, and O45 compared to the control group. In conclusion, the in-feed administration of the synbiotic product appears to reduce fecal shedding of certain top-7 STEC serogroups in the feedlot cattle.