Exploring the influence of endometritis diagnostic criteria on uterine involution, milk yield and fertility in dairy cows.

BACKGROUND: We investigated the impact of different classification schemes for postpartum uterine disease on genital tract involution, milk yield, and reproductive performance in dairy cows. The reproductive tracts of 223 Polish Holstein cows were examined between 21 and 29 days postpartum (median 24 days). Transrectal ultrasonography was employed to assess reproductive tract dimensions, vaginoscopy was used for visual scoring of vaginal discharge, and endometrial cytology with the cytobrush was used to calculate the percentage of polymorphonuclear cells (PMN). The health status of the cows was classified using two diagnostics models. Model 1 categorized cows as healthy (H; <5% PMN and absence of purulent vaginal discharge [PVD0]), subclinical endometritis (SE; ≥5% PMN and PVD0), and further subdivided PVD into three categories: flecks of pus in vaginal discharge (PVD1), mucopurulent discharge (PVD2), or purulent discharge including red-brownish watery fetid discharge (PVD3), irrespective of endometrial PMN%. Model 2 classified cows as healthy (H; <5% PMN and PVD0), subclinical endometritis (SE; ≥5% PMN and ≤ PVD1), and clinical endometritis (CE; ≥5% PMN and > PVD1).

RESULTS: Cows with ≥ PVD2 (Model 1) and CE (Model 2) had larger cervical and uterine horn diameters and were less likely to resume ovarian activity by the fourth week postpartum in comparison to H and SE. For Model 1, the milk yield to 120 days postpartum was lower in PVD3 in comparison to H while for Model 2, CE produced less milk to 120 days postpartum when compared to H or SE. For both models, SE had a lower first service conception rate than H cows, but the pregnancy risk to 210 days postpartum did not differ. When compared to H, PVD2 (Model 1), and CE (Model 2) had the lowest first service conception rate and pregnancy risk to 210 days postpartum.

CONCLUSION: Model 1 provides detailed PVD severity assessment, which is valuable for potential targeted treatment and management but adding complexity due to multiple categories. Model 2 offers simpler categorization for clear management decisions but may overlook disease nuances. Though labor-intensive and less practical for routine use, these protocols are useful for population-level decision-making in dairy farm reproductive performance.