208 Impact of Feeding a Novel Probiotic on Ruminal Fermentation, Methane Production, and Nutrient Utilization in Beef Cattle

Abstract The search for alternatives to mitigate enteric methane emissions remains a top priority to ensure the continued sustainability of the livestock industry. Exploration of new direct-fed microbials with potential in ruminant nutrition is an active and promising area of research. This study aimed to evaluate the effects of feeding a novel probiotic on ruminal fermentation parameters, in vitro methane production, and nutrient utilization in beef steers. A total of 12 ruminally cannulated American Aberdeen steers (348 ± 37 kg BW) were used in a 4 × 4 Latin square design, with each period lasting for 35 d. The steers were fed a basal diet comprised of 82% corn silage, 12% cotton gin trash, 5% cottonseed meal, and 1% vitamin and mineral supplement on a dry matter (DM) basis. Four treatments were used in this study: CTL (no additive), B2 (probiotic at a dosage of 2 × 109 CFU/animal/d), B10 (probiotic at a dosage of 10 × 109 CFU/animal/d), and B30 (probiotic at a dosage of 30 × 109 CFU/animal/d). Steers were housed in two pens and were sorted daily to receive the treatments individually in a carrier of corn silage (250 g/d). The experiment consisted of 4 periods, with 21 d of adaptation to the treatments, 7 d of measurements, and 7 d of washout between periods. During the study, two in vitro batch culture incubations were performed in each period collecting ruminal fluid from each animal individually (experimental unit): one on d 0 before steers received the treatments, and one after 21 d of adaptation. The incubations on day 0 were used as a baseline. The use of this probiotic did not affect (P > 0.05) in vitro ruminal fluid pH, volatile fatty acids, or acetate to propionate ratio. However, there was a cubic effect (P < 0.05) on in vitro organic matter digestibility with the inclusion of probiotic, and the greatest digestibility was observed in the B2 treatment. The concentration of ammonia nitrogen linearly increased (P < 0.05) with the inclusion of probiotic with CTL and B2 treatments showing the least values. While there was no effect (P > 0.05) on total gas production among treatments, methane production (CH4) was decreased (P < 0.05), showing a quadratic effect where the B2 treatment showed the least values. These results suggest that adding this novel probiotic to beef steers fed a corn silage-based diet at a dose of 2× 109 CFU per day (B2) may have positive results in reducing CH4 and improving digestibility. However, confirmation of these results