Associations between resumption of postpartum ovarian activity, uterine health and concentrations of metabolites and acute phase proteins during the transition period in Holstein cows

The resumption of ovarian activity, uterine health, severity of the negative energy balance and the synthesis of inflammatory mediators during the transition period in dairy cows are interrelated. Therefore, the aim of this study was to evaluate the association between the resumption of postpartum ovarian activity and the percentage of polymorphonuclear (PMN) cells in endometrial cytology, lipid mobilization and the secretion of acute phase proteins. For this study, 20 multiparous Holstein cows were used. Blood samples that were collected from 21 d before calving to 44 d in milk (DIM) were analyzed for serum glucose, non-esterified fatty acids (NEFA), insulin, haptoglobin, albumin, paraoxonase and progesterone. Endometrial cytology was performed at 37 ± 2 DIM to evaluate the percentage of PMN cells in the uterine flushing. Cows were divided into two groups: (1) ovulatory cows (n = 12), which returned to ovarian activity by 44 ± 2 DIM; and (2) anovulatory cows (n = 8), which did not resume ovarian activity during this period. Ovulatory cows had a lower (P = 0.05) percentage of PMN cells in endometrial cytology than anovulatory cows (26.3 ± 8.3% vs. 53.4 ± 16.9%, respectively). Ovulatory cows had higher serum albumin during the pre- (P = 0.03) and postpartum periods (P = 0.01), and tended to have lower haptoglobin concentrations in the prepartum period (P = 0.07) and higher paraoxonase activity in the postpartum period (P = 0.09). In conclusion, cows that resumed ovarian activity early in the postpartum period had higher albumin concentrations in the peripartum period, which were associated with a lower percentage of uterine PMN cells.