Association of Moderate and High Vaginal Discharge Scores up to 21 Days Postpartum with Adverse Effects on Days Open and Pregnancy Rate in Dairy Cows

Uterine health indicators are essential tools for managing reproduction in dairy herds. This study evaluated the associations between vaginal discharge scores (VDS) assessed during the first 21 days postpartum and subsequent days open and pregnancy rate (PR) across 14 commercial dairy herds comprising 2860 calvings (2023–2025). VDS were evaluated on a 10-point scale and classified as normal (0–2; clear/bloody), moderate (3–4; presence of pus), or high (5–9; purulent and foul-smelling). Concurrently, parity, metabolic (body condition score and acetonuria), and digestive (fecal consistency) indicators were recorded. Two independent multivariate models, Cox proportional-hazards regression and binary logit generalized linear mixed model (GLMM), were used. VDS was the most significant and consistent factor associated with prolonged days open and reduced PR. A higher hazard ratio (HR) for pregnancy failure was observed in cows with moderate (HR = 1.45; 95% CI: 1.20–1.65) and high (HR = 1.59; 95% CI: 1.25–2.01) VDS compared with those with normal VDS (p < 0.0001), thereby extending the days open at the first artificial insemination. The odds ratio (OR) for becoming pregnant at the first artificial insemination was lower (p < 0.01) in cows with moderate (OR = 0.5; adjusted 95% CI: 0.4–0.8) and high (OR = 0.4; adjusted 95% CI: 0.3–0.8) VDS than in those with normal VDS. This likelihood was also lower for multiparous cows compared with primiparous cows (p < 0.001). No other factors were significantly associated with PR (p > 0.05) in the GLMM. In conclusion, scoring vaginal discharge in the early postpartum period was a relevant health indicator associated with days open and PR. Implementing specific reproductive management protocols for cows presenting moderate VDS is suggested to improve overall herd reproductive performance.