Rumen Micrbiota in High-producing Dairy Cows

Antibiotic resistance is a pressing global issue, and the bovine rumen is widely acknowledged as a substantial reservoir of ARGs. Nevertheless, within intensive farming systems, the composition and dissemination patterns of rumen microbial communities and ARGs across cows with varying lactation capacities remain poorly understood. In this study, rumen fluid was collected from 8 higher-milk-yielding cows (HM) and 8 lower-milk-yielding cows (LM) selected from 90 mid-lactation Holstein cows. Quantitative metagenomics and untargeted metabolomics were employed to investigate the characteristics and transmission pathways of rumen microbial communities and ARGs in cows with different milk yields. We observed that high-yielding cows exhibited stronger carbohydrate metabolism capacity, higher Chao1 and ACE indices, and fewer microbial counts. Moreover, high-yielding cows displayed reduced absolute abundances of bacteria and viruses, increased relative abundances of archaea and eukaryotes, and a more intricate microbial network architecture. These shifts contributed to a reduction in ARG prevalence, particularly within peptide, elfamycin, and fluoroquinolone antibiotic categories, and were accompanied by a streamlined ARG interaction network. Furthermore, the attenuation of ARGs was largely attributable to reduced levels of MGEs, especially those linked to replication, phage activity, genetic transfer, and defense functions. These findings underscore the pivotal role of the microbial structure - MGE - ARG co-occurrence network in maintaining rumen health and shaping microbial ecology. Collectively, our results elucidate the mechanisms governing microbial and ARG colonization and transmission in cows with divergent lactation capacities, thereby informing One Health oriented strategies for intensive farming management and offering novel insights into sustainable and efficient dairy production.