Short communication

________________________________________________________________________________ Abstract Megasphaera elsdenii (M.e.) NCIMB 41125 is a robust lactate utilizing strain of M.e. that is effective in minimizing the risk of ruminal acidosis in feedlot cattle. When dosed orally, cattle adapt smoothly to increasing concentrates in the diet, the incidence of digestive disturbances, morbidity and mortality is reduced, and carcass yield improves. One could therefore expect that the smooth transition should benefit overall performance. Dosing with the organism also provides the opportunity of a reduction in the time necessary for adaptation, rendering a further decrease in the cost of feeding. These two objectives were tested with 80 yearling crossbred steers blocked by weight before allotment to the respective treatments. The trial design was a randomized 2 × 2 factorial of two drench treatments (M.e. vs. placebo) and two adaptation periods (17 vs. 8 days). In the M.e. treatment, 40 steers were dosed orally on day 1 of the trial with 200 mL inoculum containing 10 11 cells. In the placebo treatment, the other 40 steers were dosed orally with only the 200 mL inoculum. In the 17-day transition period, five diets (5–transition) were used, which increased progressively in concentrate percentage, whereas in the 8-day transition period only three of the five diets were fed (3–transition). The steers were fed individually for 63 days before being transferred to group pens and fed until day 95, when they were slaughtered. Dry matter intake was not affected by dose or transition treatment. Body weight at 28 days and 63 days did not differ between dose and transition treatments; neither did ADG and FCR. Hot carcass weight was higher in M.e. steers than in placebo steers. None of the parameters differed significantly between the 5–transition and the 3–transition treatments. It was concluded that dosing with M.e. NCIMB 41125 should provide a small benefit to performance of feedlot cattle, with a further benefit in cost savings as dosing with the organism should allow a shorter adaptation period. ________________________________________________________________________________