310 Evaluation of Orally Administered Megasphaera Elsdenii in Preconditioned Calves Abruptly Transitioned from a Receiving Diet with 4% Dietary Starch to a Growing Diet with 37% Dietary Starch

Abstract

Abstract The objective of this study was to evaluate the effects of orally administered Megasphaera elsdenii NCIMB 41125 (ME) in preconditioned calves abruptly transitioned from a receiving diet with 4% dietary starch [dry matter (DM) basis] to a growing diet with 37% dietary starch (DM basis). Preconditioned steers [n = 192; initial shrunk body weight (SBW) = 309 kg ± 20.6 kg] were assigned to microbial supplement treatment in a randomized complete block design. Treatments were CON: no ME; and LP: orally administered 20 mL of microbial supplement (2 × 1010 colony forming units ME/mL) immediately before diet change. Steers were abruptly changed from a receiving diet based upon soybean hulls and wheatlage with 4% dietary starch (DM basis) to a growing diet based upon high-moisture ear corn, dry-rolled corn, and wheatlage with 37% dietary starch (DM basis). Diets were switched on an equal DM basis to achieve abrupt change and steers were fed treatment diet for 49 d until study completion. Prior to study initiation, steers (n = 72; n = 3/pen) were fitted with wireless rumination tags to track daily activity and rumination time. Growth performance data and efficiency of dietary net energy utilization were analyzed with pen as the experimental unit, fixed effect of treatment, and random effect of block (location in the feedlot). Activity and rumination data were analyzed in a repeated measures analysis of covariance with individual animal as experimental unit, fixed effects of treatment, week, and their interaction, block (location in feedlot) as a random effect, and baseline activity and rumination as a covariate in the model. If no interaction was observed, main effect means of treatment and week were evaluated independently. For all statistical analysis, P ≤ 0.05 was declared significant and P ≤ 0.10 was declared a tendency. No difference (P ≥ 0.20) was observed between treatments for final SBW, average daily gain, dry matter intake, feed efficiency, calculated net energy (NE) for maintenance and gain or observed-to-expected ratio of NE for maintenance and gain. Additionally, no treatment × day differences (P ≥ 0.27) were observed for activity or rumination measures. Treatment effects (P < 0.01) were observed for both activity and rumination where LP steers had a 2% increase and 2% decrease in minutes per day active and ruminating respectively. Additionally, a positive linear effect (P < 0.01) of week was observed for minutes ruminating and quadratic effects (P < 0.01) of week were observed for minutes active and ruminating. Oral administration of ME had no effects on growth performance or efficiency of dietary net energy utilization in steers transitioned from a receiving diet containing 4% starch (DM basis) to a growing diet containing 37% starch (DM basis).