Co-relation between cytokine dynamics and uterine microbiota in postpartum dairy cows with purulent vaginal discharge

Postpartum uterine infections with purulent vaginal discharge (PVD) impair reproductive efficiency in dairy cows. Cytokines regulate the immune response to bacterial colonisation, but their relationship with uterine microbiota remains unclear. This study aimed to evaluate the relationship between cytokine dynamics and uterine microbiota, providing insights into immune responses and microbial dysbiosis. Sixteen Holstein cows (PVD = 8, healthy = 8) were sampled at 21, 28 and 35 days postpartum (dpp). PVD was diagnosed using the gloved hand method based on mucus score (≥ 2). Blood samples were analysed for interleukin (IL-6, IL-10) and tumor necrosis factor-alpha (TNF-α) via ELISA. Endometrial samples were collected using cytobrushes and 16S rRNA sequencing was performed to assess microbial composition. Data were analysed using mixed linear regression models and Pearson correlation. At 21 dpp, PVD cows had significantly higher IL-10 levels (45 ± 3.9 vs. 32 ± 2.7 ng/L, p < 0.05) and showed significant differences in alpha & beta diversity, with higher relative abundances of Fusobacterium, Porphyromonas, Trueperella and Parvimonas compared to healthy cows (p < 0.05). IL-10 levels showed a strong positive correlation with Fusobacterium (r = 0.65, p < 0.05) and Porphyromonas (r=0.58, p < 0.05). After antibiotic treatment, at 28 and 35 dpp, microbial diversity partially recovered, pathogen abundance decreased, and IL-10 remained elevated during recovery before gradually declining with healing. These findings suggest that IL-10 upregulation in PVD cows is linked to microbial dysbiosis, particularly Fusobacterium and Porphyromonas overgrowth, potentially driving inflammation. Targeted modulation of immune responses and microbial balance may improve reproductive outcomes in postpartum dairy cows.