Differences in the microbial community abundances of dairy cattle divergent for milk urea nitrogen and their potential implications

Objective: The first objective of this experiment was to determine and describe any differences in rumen micro-biota relative abundances between dairy cattle divergent for MUN breeding values (MUNBV). The second objective was to ascertain whether any differences in rumen microbiota relative abundances may be associated with phenotypical differences already observed in dairy cattle divergent for MUNBV. Materials and Methods: Rumen microbiota data were collected and collated from multiple trials that had been conducted investigating differences in dairy cattle divergent for M UMW where rumen samples were taken via esophageal incubation. Results and Discussion: On average 8% of the rumen microbiota genera detected differed in their relative abundance based on MUNBV. High-MUNBV dairy cattle had a 10% increase in the relative abundance of Basfia and a 20% increase in the relative abundance of Succinivibrio compared with low-MUNBV dairy cattle. Both Basfia and Succinivibrio have potential implications for rumen fermentation that require further investigation. High-MUNBV dairy cattle also had a 17% increase in the relative abundance of Kandleria compared with low-MUNBV dairy cattle. Greater relative abundances of Kandleria may be affecting the health status of dairy cattle classified as high MUNBV resulting in greater incidences of increase SCC. Implications and Applications: Knowledge of differences in the relative abundance of the rumen rnicrobiota of dairy cows divergent for MUNBV highlights areas where future research is required as well as the potential for using MUNBV as a metric for increasing animal welfare.