Invited Review: Advances in rumen efficiency

ABSTRACT Purpose The purpose of this review was to explain how advances in our knowledge of rumen microbial ecology provide opportunities to improve ruminal fiber degradation, decrease enteric methane production, and limit wastage of dietary protein without disrupting ruminal efficiency. Sources Peer-reviewed literature was the primary course of information reviewed. Synthesis As numbers of microbial taxa in the rumen have expanded in the past 10 yr, we have gained appreciation for why rumen efficiency is so variable among dietary situations and even among dairy cattle fed the same diets. In typical dairy rations with mixed forage and grain, the primary fibrolytics support a balanced community. However, that community can be disrupted and thus limit fiber digestibility or DMI unless forage quality and particle size along with RDP are maintained. Efforts to decrease enteric methane or improve the efficiency of dietary protein usage should appreciate the complexity of the microbial community to improve consistency of responses. Conclusions and Applications Many feeding practices indirectly influence the rumen microbial structure and function, and future opportunities for feed additives will likely be adjusted for likelihood of benefit using microbial sequence data.