336 Evaluation of a Bacillus Spp. Probiotic on Beef Cattle Performance, Nutrient Digestibility and Enteric Methane Emissions

Abstract Direct-fed microbials have been used in an effort to improve livestock production efficiency and reduce environmental impact. Among other species, spore forming bacteria such as Bacillus spp. present handling and processing advantages to be used as a probiotic. Several studies have demonstrated positive effects of Bacillus spp. on dairy cattle production. However, there is lack of information about its effects on beef cattle. Thus, the objective of this study was to evaluate the effect of a probiotic composed by a mixture of B. subtilis and B. licheniformis on beef cattle performance, nutrient utilization, and enteric methane emissions (CH4). For this purpose, a total of 108 Angus crossbred heifers (318 ± 40.4 kg of BW) were used in a generalized randomized block design. The heifers were fed a sorghum silage-based diet containing 1 of the 2 following treatments: 1) control (CTL, no additive), or 2) Bacillus spp. probiotic (BSL, 310 mg/kg of diet DM), in an attempt to provide an average of 3 g·animal-1·d-1. The experimental period consisted in 7 d of adaptation to the pens, followed by 77 d of performance data collection, 5 d of apparent total tract digestibility measurements, and 5 d of CH4 measurements. No effect of treatment (P > 0.05) was observed for dry matter intake, average daily gain, or gain-to-feed ratio. The inclusion of the probiotic did not affect (P > 0.05) apparent total tract digestibility of dry matter, organic matter, neutral detergent fiber and crude protein, whereas starch digestibility decreased (P = 0.027) with the probiotic inclusion. No differences (P > 0.05) were observed for CH4 between the two treatments. Accordingly, feeding Bacillus spp. did not affect cattle performance, nutrient utilization, or enteric CH4 emissions in beef heifers when included at 310 mg/kg of dietary dry matter.