Abstract: There is an increasing interest in studying rumen microbiota in dairy cow nutritional trials in recent years,aiming to link its compositional changes to the feed composition,performance traits（i.e. feed efficiency,milk yield,milk fat,etc.）,health related traits（i.e. ruminal acidosis and subacute acidosis）as well as environmental traits（i.e. methane emission）. Additional researches have highlighted the role of microbiota in rumen development in multiple ruminant species. The majority of the findings on the rumen microbiota are based on the sequencing of the marker gene amplicon,which gives the picture of the taxonomic microbial composition and how it shifts under different treatments. Although the emerging metagenomic and metatranscriptomic analyses enabled in-depth exploring of the rumen microbial functions,it also generated more challenges in data analysis and interpretation. Up to date,most of the papers heavily rely on correlation and speculation analysis without clearly clarifying the mechanisms behind. In this paper,we reviewed the progress and limitation of dairy cow rumen microbiota,including the relationship between rumen microbiota and milk production efficiency,methane emission and rumen development,and we also discussed the research trends of rumen microbiota in dairy cows.

Key words: rumen microbiota, dairy cow, milk production efficiency, methane emission, rumen development