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 (CH 4 ) 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 × 10 8 (low; L), 2.5 × 10 9 (medium; M), or 2.5 × 10 10 (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 P  = 0.005), and energy metabolizability ( P 4 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 CH 4 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 CH 4 production to digestible DM intake in the L, M, and H groups was lower than that in the control ( P B. licheniformis supplementation effectively reduced in vivo methane emissions from sheep with concomitant improvement of their energy and protein utilization.