Association between evaluation of the reproductive tract by various diagnostic tests and restoration of ovarian cyclicity in high-producing dairy cows

The uterine condition of clinically normal postpartum Holstein-Friesian dairy cows (n = 45) was evaluated once weekly (Weeks 3 to 7) by endometrial cytology, vaginal mucus collection device (VMCD), vaginoscopy, and ultrasonography to establish a relationship with postpartum resumption of ovulatory cycles. The time of first detection of the corpus luteum (CL) by ultrasonography and plasma progesterone concentration ≥1 ng/mL was recorded. By 49 d postpartum, 78% of the cows (n = 35) had resumed ovarian function (CL group), whereas the remainder (n = 10) had no CL (NCL group). There was a positive correlation between VMCD score and presence of fluid in the uterus in cows with a CL (P < 0.01) during Week 3 postpartum but no significant correlation in cows without a CL. Percentage of polymorphonuclear leukocytes (PMN%) was higher in the NCL group (mean ± SEM, 24.6 ± 9.4%) than in the CL group (11.7 ± 2.2%) during Week 5 postpartum (P < 0.05). The PMN% (4.5 ± 6.5%) and VMCD (0.5 ± 0.5) scores during Week 5 in cows ovulating by Day 28 were lower (P < 0.01) than the PMN% (15.0 ± 14.3%) and VMCD (1.1 ± 0.9) scores in those ovulating by Day 49. In conclusion, higher PMN% at 5 wk postpartum was associated with delayed resumption of ovarian cyclicity in high-producing dairy cows.