Cytological endometritis in dairy cows: diagnostic threshold, risk factors, and impact on reproductive performance

We determined the threshold proportion of polymorphonuclear leukocytes (PMNs) for a diagnosis of cytological endometritis (CEM), the risk factors for this condition, and its impact on reproductive performance in dairy cows. Uterine cytology was performed on 407 Holstein cows 4 weeks postpartum to determine the proportions of endometrial cells and PMNs. A receiver operator characteristics curve was used to determine the threshold above which the PMN proportion affected the likelihood of cows conceiving by 200 days postpartum. The optimal threshold was ≥ 14% PMN (sensitivity, 31.3%; specificity, 81.7%; p ＜ 0.05). The farm identity, retained placenta (odds ratio [OR] = 1.87), and septicemic metritis (OR = 3.07) were risk factors for CEM (p ＜ 0.05). Cows with CEM were less likely to resume cyclicity (OR = 0.58) and to conceive by 200 days postpartum (hazard ratio = 0.58). Cows with CEM tended (p ＜ 0.1) to be less likely to become pregnant after their first insemination (OR = 0.65) and to require a greater number of inseminations per conception (2.3 vs. 2.2). In conclusion, a PMN threshold of 14% defined the presence of CEM at 4 weeks postpartum. The farm, retained placenta, and septicemic metritis were risk factors for CEM, which reduces subsequent reproductive performance.