Ruminal fermentation, nutrient metabolism, and methane emissions of sheep in response to dietary supplementation with Bacillus licheniformis

Abstract

Some bacterial preparations have been used as rumen methane (CH4) mitigants, but the effect of the spore-forming bacterium Bacillus licheniformis on ruminal methanogenesis is unknown. In this study, twenty-four Dorper crossbred wethers (45.0 ± 1.96 kg of body weight) were randomly assigned to 4 dietary treatments (6 animals/treatment): a basal diet (control), or the basal diet supplemented with 2.5 × 108 (low; L), 2.5 × 109 (medium; M), or 2.5 × 1010 (high; H) colony-forming units of B. licheniformis per animal per day. Ruminal fermentation characteristics, apparent digestibility and metabolism of nutrients and gross energy, and in vivo methane emissions were measured. The L group had lower ruminal ammonia nitrogen concentrations than the control (78.5 vs. 100.8 mg/L; P = 0.001). Dietary B. licheniformis supplementation enhanced the apparent digestibility of dry matter, organic matter, N, and neutral detergent fiber (P < 0.001), improved the N retention and utilization efficiency (P = 0.005), and energy metabolizability (P < 0.001). Daily CH4 production in the L and M groups was lower than that in the control (39.9 and 39.8 vs. 42.5 L/d; P = 0.017 and 0.011, respectively), and these effects were also mirrored by relative CH4 production to dry matter (DM) intake (31.7 and 31.6 vs. 33.8 L/kg DM intake; P = 0.017 and 0.012, respectively). Relative CH4 production to digestible DM intake in the L, M, and H groups was lower than that in the control (P < 0.001). Dietary B. licheniformis supplementation effectively reduced in vivo methane emissions from sheep with concomitant improvement of their energy and protein utilization.