Integrated rumen microbial, functional, and metabolic features explain divergent milk urea nitrogen phenotypes in dairy cows

Dietary energy protein balance and the metabolic and physiological status of cows can be better understood by monitoring milk urea nitrogen (MUN). Recent studies revealed the role of gastrointestinal microbiota in influencing host phenotypes; however, the contribution of rumen microecology and metabolism to MUN remains poorly understood. This study was designed to explore ruminal microecological, functional, and metabolic distinctions between high (HMUN) and low MUN (LMUN) cows and to evaluate their respective contributions to the emergence of divergent MUN phenotypes.