Evaluating the relationships between anti-Müllerian hormone, milk production, estrous expression and first service conception rate in lactating dairy cows.

Anti-Müllerian hormone (AMH) concentrations are positively associated with antral follicle count (AFC) and may serve as a biomarker of overall fertility in dairy cattle. This study aimed to determine whether circulating AMH concentration in lactating dairy cows is associated with milk production, estrous expression and first service conception rate (FSCR) by breeding protocol. Primiparous and multiparous (n = 245) purebred, lactating Holstein cows were enrolled at 45-60 days in milk (DIM). Blood was collected at enrollment for AMH and transrectal ultrasonography was performed to record AFC, corpora lutea (CL) and cyclicity status. Animals were bred either to an estrous detection (n = 152) or timed artificial insemination (TAI) (n = 93). Seven-day average milk-weight (7D milk weight) on the day of sampling and breeding, DIM at breeding and FSCR were recorded. Animals were retroactively blocked by AMH concentration into HIGH (>282 pg/mL; n = 83) MID (167-278; n = 84) and LOW (<165 pg/mL; n = 78) categories for analysis. The FSCR was not impacted (P > 0.05) by AMH category, breeding protocol or DIM, however, greater 7D milk weight (P = 0.03) and increased age (P = 0.08) tended to increase FSCR. AMH concentration was increased in cows with increased AFC (P < 0.01), 7D milk weight (P = 0.05) and lactation number, 7D milk weight interaction (P = 0.03). In conclusion, FSCR was not related to AMH category or breeding program. In this study, older, higher producing animals had increased AMH concentrations and were more likely to display estrus and thus bred to an estrous detection protocol than a TAI protocol. The relationship between age and AMH concentration on estrous expression post-calving warrant further investigation.