Longitudinal study of the udder microbiome using genome-centric metagenomics uncovers pathogen-driven adaptation and succession.

Bovine mastitis remains a major disease affecting dairy herds globally due to its complex and multi-etiological nature. To address gaps in microbial and immunological understanding, this longitudinal study examined the udder microbiome across lactation in 24 Norwegian Red cows. Somatic cell count (SCC) and microbiota composition varied by lactation stage, with low SCC ( < 100,000 cells/mL) more frequent in early (80%) and middle (78.9%) than late lactation (53%) and dry-off (53.1%). Microbial diversity was shaped by SCC, lactation stage, and individual variability. Temporal profiling identified persistent infections involving Staphylococcus aureus and Staphylococcus chromogenes, while samples with low SCC were enriched in beneficial genera including Corynebacterium, Bradyrhizobium, and Lactococcus. Shotgun metagenomics revealed pathogen-specific metabolic traits, and genome-centric analysis recovered 142 MAGs characterized via sequence typing, virulence, and resistance profiling. These findings offer valuable insights into microbial adaptation and succession, informing strategies to better manage and prevent mastitis.