Assessment of anti-Müllerian hormone levels as a reproductive indicator in Japanese Black cattle.

The size of the ovarian reserve, an indicator of the number of primordial follicles, varies widely among individuals, and declines with age. However, the association between the ovarian reserve and fertility remains unclear. Therefore, in the present study, we analyzed the relationship between plasma concentrations of anti-Müllerian hormone (AMH), a marker of ovarian reserve, and reproductive outcomes in Japanese Black cattle. AMH level quartiles were positively associated with pregnancy following artificial insemination (AI), and the median number of days to pregnancy in Q4 (13 days, 95% confidence interval [CI] = 7-18 days) was significantly shorter than that in Q1 (21 days, 95% CI = 15-46 days). The odds ratio for the predicted pregnancy rate by logistic regression analysis in Q4 (4.06, 95% CI = 1.54-10.67) was also significantly higher than that in Q1. Plasma AMH concentrations were significantly higher in summer (June-August) than in winter (December-February). Furthermore, a strong correlation (r = 0.829, P < 0.001) was observed between plasma AMH concentrations at 2 and 14 months of age. Calves with plasma AMH concentrations of > 700 pg/ml at 2 months old showed a transient increase and maximum AMH concentration within 5 months of birth. Overall, the results of this study indicate that the plasma AMH concentration serves as a predictive marker for the probability of conception following AI in Japanese Black cattle. The current findings contribute to the reliable assessment of AMH production and the early prediction of reproductive performance in sexually mature heifers.