Association between polymorphonuclear leukocytes in the cervical mucosa and fertility in dairy cows

Abstract

The relationship between cervicitis and fertility has been poorly studied in dairy cows. Endocervical inflammation, determined by an increase of polymorphonuclear leukocytes (PMN), is linked with lower hazard of pregnancy. The objective of the present study was to evaluate if an increase in PMN in the cervical mucosa is associated with decreased fertility in dairy cows. Endocervical samples were collected from dairy cows (n = 243) between 30 and 40 days postpartum. All cows had completed their uterine involution and did not show clinical uterine diseases. A cytological sample was taken by passing the first ring of the cervix using an endocervical brush. A smear was made and stained using the diff quick technique. One hundred cells were counted, and the proportion of PMN was obtained. The cut-off point for the percentage of PMN that corresponded to a decrease in fertility was obtained by analyzing the ROC curve. The cut-off point for the proportion of PMN influencing a decreased fertility was 6%. Thirty-five percent (86/243) of the cows had ≥ 6% PMN. The conception rate at first service was higher in cows with < 6% PMN (43%) than in cows with ≥ 6% PMN (31.4%) [odds ratio = 1.74, CI = 1.0–3.0 (P = 0.047)]. The cumulative proportion of pregnant cows at day 210 postpartum was higher in cows that had < 6% PMN (82%) than cows with ≥ 6% PMN (69%) [odds ratio = 2.2, CI = 1.1–3.9 (P = 0.017)]. Cows with < 6% PMN had a reduced interval from calving to conception than cows with ≥ 6% PMN [97 days (89–106 days) vs. 110 days (89–123 days); median (95% CI); P < 0.05]. In conclusion, a higher proportion of PMN in the cervical mucosa is associated with decreased fertility in dairy cows.