Assessment of the physical and chemical properties of vaginal discharge for the diagnosis of endometritis in dairy cattle.

Background and aim: Postpartum endometritis is a major cause of infertility in dairy cattle, impacting herd productivity and economic sustainability. Although traditional diagnostic methods are available, there remains a need for simple, rapid, and accurate cow-side diagnostic tools to facilitate early detection and management of clinical endometritis (CE) and subclinical endometritis (SCE). This study aimed to (i) evaluate the diagnostic performance of vaginal discharge parameters - pH, total dissolved solids (TDS), salinity, and electrical conductivity (EC) - using a portable flat-surface electrode probe, and pH and leukocyte esterase (LE) activity using reagent strips and (ii) establish optimal cut-off values for these parameters to support practical on-farm screening of endometritis.

Materials and methods: Fifty-eight postpartum Holstein Friesian cows were enrolled. Vaginal discharge was collected using a Metricheck device and analyzed for pH, TDS, salinity, and EC. Concurrently, pH and LE activity were assessed using reagent strips. Endometrial cytology was performed to diagnose CE and SCE. Diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis.

Results: pH values measured by both the meter and strip were significantly higher in cows with normal uterine health compared to those with CE (p = 0.010 and p = 0.008, respectively). LE activity was significantly elevated in cows with CE (p = 0.001). ROC analysis identified optimal cut-off values: pH meter ≤8.35 (area under the curve [AUC] = 0.768) and LE strip ≥2 (AUC = 0.835) for diagnosing CE. Combining pH and LE strip results improved diagnostic performance (AUC = 0.801), achieving 65.22% sensitivity, 87.5% specificity, and 76.6% accuracy. TDS, salinity, and EC were not significantly associated with uterine health status (p > 0.05).

Conclusion: The combined evaluation of vaginal discharge pH and LE activity offers a practical, cost-effective cow-side screening method for diagnosing endometritis in dairy cattle. In contrast, TDS, salinity, and EC measurements were not diagnostically informative. The proposed approach may enhance herd health management by enabling timely identification and treatment of endometritis.