Associations between serum calcium concentration and postpartum health and reproductive performance in dairy cows.

In the present study, the aim was to evaluate the associations between serum calcium concentration after calving and serum metabolites, postpartum disorders, and reproductive performance in dairy cows. Blood samples were collected from 200 Holstein cows immediately and 1, 2, 4, 6, and 8 weeks after calving to measure serum metabolites and progesterone concentrations. Cows were divided into three groups on the basis of the mean serum calcium concentration after calving: a Low group (<7.9 mg/dL, n = 52), a Moderate group (7.9-9.6 mg/dL, n = 100), and a High group (≥9.7 mg/dL, n = 48). Total cholesterol (TCH) concentration was greater in the High group than in the Moderate group during the postpartum period (P <  0.01). The High group had greater albumin concentrations during the postpartum period (P <  0.01) and glucose concentrations after calving and 1 week postpartum (P <  0.05) than the Low and Moderate groups. The High group had a lesser incidence of retained placenta than the Low (P <  0.1) and Moderate (P <  0.01) groups, and a lesser incidence of clinical endometritis than the Moderate group (P <  0.05). The probability of resuming estrous cyclicity by 8 weeks postpartum was greater in the High group than in the Low group (hazard ratio = 3.71, P <  0.05). In conclusion, greater serum calcium concentration after calving is associated with greater serum TCH, albumin, and glucose concentrations, a lesser incidence of retained placenta, and clinical endometritis, and earlier resumption of estrous cyclicity in dairy cows.