Systemic oxidative stress is associated with coordinated alterations in uterine microbiota and glutathione-related metabolism in postpartum dairy cows.

The transition from late gestation to early lactation exposes dairy cows to substantial metabolic and oxidative challenges. However, the relationship between systemic oxidative stress and the postpartum uterine microenvironment remains poorly understood. This study investigated whether systemic oxidative stress is associated with alterations in the uterine microbiota and metabolic profiles in postpartum dairy cows, and explored the potential biological relevance of these changes using an in vitro endometrial epithelial cell model. Eighty Holstein cows were screened at 7 days postpartum using their oxidative stress index (OSI). Individuals with extreme values were classified into high oxidative stress (HOS, n = 10) and low oxidative stress (LOS, n = 10) groups. Uterine flushing samples were subjected to 16S rRNA gene sequencing and untargeted metabolomic analysis. Compared with LOS cows, HOS cows showed reduced microbial richness and diversity, distinct community composition, and enrichment of inflammation-associated taxa. Metabolomic analysis revealed clear metabolic separation between the groups and coordinated shifts in multiple metabolic pathways. Glutathione metabolism emerged as a central node potentially linking oxidative stress and uterine metabolic remodeling. Integrated analyses further demonstrated structured associations among OSI, uterine microbial community structures, and the metabolites involved in redox regulation. In vitro experiments using bovine endometrial epithelial cells showed that Lactobacillus rhamnosus GG treatment partially mitigated oxidative stress-related indicators under inflammatory conditions. These findings suggest that systemic oxidative stress is associated with coordinated changes in the uterine microbiota and metabolic networks in postpartum dairy cows, particularly involving glutathione-related pathways, although the causal relationships require further investigation.