Effects of oat hay and leguminous forage mixture feeding on enteric methane emission, energy utilization, and feed conversion efficiency in male crossbred Simmental beef cattle

Dietary manipulation has the potential to mitigate methane (CH 4 ) emission and to maintain or enhance livestock productivity. We conducted two experiments to investigate the effects of replacing oat hay by leguminous forages (alfalfa hay [AH], 0, 8, 16, and 24%, experiment 1; common vetch hay [CVH], 0, 10, 20, and 30%, experiment 2) on energy metabolism of crossbred Simmental cattle. In experiment 1, total volatile fatty acid (VFA) concentrations increased quadratically with increasing AH proportions ( p  = .006) with a forage‐to‐concentrate ratio of approximately 50:50, whereas the CH 4 energy to gross energy intake ratio (CH 4 ‐E:GEI) was significantly lower with 16% AH compared with 24% AH diet ( p  < .05). In experiment 2, there were no differences in the total VFA concentrations among the four diet groups with a forage‐to‐concentrate ratio of around 60:40 ( p  > .05); however, CH 4 ‐E:GEI was significantly lower in the 30% CVH diet compared with the 10% CVH diet ( p  < .05). There was no significant difference in feed conversion efficiency among the four diet groups in each experiment. The results suggest that substituting 16 and 30% oat hay by AH and CVH provide optimal diets with forage‐to‐concentrate ratios of 50:50 and 60:40, respectively, which may reduce CH 4 emission without compromising the feed conversion efficiency of crossbred Simmental cattle.