Reduced Carriage of Escherichia coli O157:H7 in Cattle Fed Yeast Culture Supplement

The effect of Saccharomyces cerevisiae fermentation product on cattle carriage of Escherichia coli O157:H7 (O157) was assessed using 8 one-yr-old Charolais heifers equipped with ruminal cannulae in a 64-d trial. Animals were confirmed negative for O157 before the initiation of the trial and until bacterial challenge. Alfalfa hay and grain were fed twice daily with ad libitum water access. Animals were randomly assigned to control (200 g/d ground barley) or XP-fed (56 g/d Diamond V XP yeast culture mixed with 144 g ground barley) groups. Animals were challenged with 10¹⁰ cfu O157 through the rumen cannula on d 30. Recto-anal junction mucosal swab and rumen fluid samples were cultured for O157 twice a week postchallenge. On d 1 postchallenge, O157 in the rumen of the XP-fed heifers was less (P = 0.043) than in control heifers (5.40 × 10² and 2.43 × 10³ cfu/ml, respectively). By d 4 postchallenge, all XP-fed heifers had cleared O157 from the rumen, whereas 2 of 4 control heifers still harbored the bacteria in that compartment. In addition, O157 recovered from recto-anal junction mucosal swabs was less (P = 0.021) in the XP-fed heifers compared with the controls on d 1 (9.23 × 10⁴ and 5.93 × 10⁵ CFU/swab, respectively) and by d 11 postchallenge, 2 of 4 XP-fed heifers were O157 culture-negative whereas all control heifers remained culture-positive through d 25 postchallenge. Thus, cattle fed the S. cerevisiae fermentation product carried fewer O157 for a shorter duration than the control heifers.