Effects of including β1–4 galacto-oligosaccharides, lactic acid bacteria or yeast culture on methanogenesis as well as energy and nitrogen metabolism in sheep

Effects of adding yeast culture (YC), lactic acid bacteria (LAB) and β1–4 galacto-oligosaccharides (GOS) on rumen methanogenesis, energy and N utilization in sheep were evaluated. The YC (Trichosporom sericeum, (1.2–2.3) × 107 colony-forming units [cfu]/g), LAB (Leuconostoc mesenteroides subsp. Mesenteroides, (1.5–1.8) × 109 cfu/g) and GOS were added to a basal diet of 40% timothy hay, 30% alfalfa hay cube and 30% concentrate on DM basis. Four wethers fitted with ruminal fistulas were assigned in a 4×4 Latin square design consisting of a digestion study succeeded by a respiratory study. Dietary treatments were: (1) basal diet (control); (2) basal diet plus 20 g GOS; (3) basal diet plus 4 g YC; (4) basal diet plus 1 g LAB/kg feed. Hemicellulose digestibility was higher (P<0.002) in sheep receiving the control treatment as compared to GOS. Ruminal pH was higher (P<0.05) in sheep receiving YC supplemented diet and tended to be higher (P=0.06) in GOS diet than sheep receiving the control diet. However, ruminal oxidation–reduction potential (ORP) was higher (P<0.05) for GOS versus control sheep. Ruminal ammonia N was reduced (P<0.05) in GOS diet compared to control and other treatment diets. The acetate:propionate ratio was lower (P=0.013) for GOS-supplemented diets compared to control. There was a reduction (P<0.05) in methane production (L per day) in GOS and YC supplemented diets compared to control. Heat production was also lower (P<0.05) for GOS and YC supplemented diets compared to control. Therefore, retained energy tended (P=0.176 and 0.072, respectively) to be higher in GOS and YC supplemented diets compared to the control. Results suggest that GOS and YC supplementation could reduce methane emission and increase energy retention in ruminants fed diets containing hay and concentrates.