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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 = 0.856, 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.

Although hormonal induction of parturition in cattle results in the successful delivery of healthy calves, the risk of retained fetal membrane is significantly increased. In a previous study, a combination of the long-acting glucocorticoid, triamcinolone acetonide, with a high dose of betamethasone partially normalized the placentomal gene expression during parturition; however, the incidence of retained fetal membrane remained high. This study further explored placentomal dysfunction and aimed to elucidate the mechanism of retained fetal membrane in parturition-induced cows. In this study, transcriptome analysis revealed that enhanced glucocorticoid exposure normalized the expression of a substantial fraction of genes in the cotyledons. In contrast, a significant reduction in the multiple signaling pathway activities, including interferon signaling, was found in the caruncles during induced parturition. Real-time PCR showed that the expression of interferon-tau in the caruncles, but not interferon-alpha or interferon-gamma, was significantly lower in induced parturition than spontaneous parturition. Interferon-stimulated gene expression was also significantly decreased in the caruncles during induced parturition. These results indicate that interferon signaling could be important for immunological control in placentomes during parturition. Additionally, this suggests that interferon-tau might be a pivotal ligand for interferon receptors in the caruncles. This study revealed that peripheral blood leukocytes in prepartum cows transcribed interferon-tau. Macrophage infiltration in the placentome is known to participate in the detachment of the fetal membrane from the caruncle. Thus, this study raised the possibility that immune cells migrating into the caruncles at parturition may act as a source of ligands that activate interferon signaling.