Plasma anti-Müllerian hormone in adult dairy cows and associations with fertility.

The objectives of this study were to identify factors associated with concentrations of anti-Müllerian hormone (AMH) in plasma of dairy cows and to investigate the relationships between plasma AMH and fertility responses during a 100-d breeding season. Lactating cows, 1,237 in 2 seasonally calving herds, had estrous cycles presynchronized and were enrolled in a timed artificial insemination (AI) protocol. All cows were inseminated on the first day of breeding season, considered study d 0. Blood was sampled on d -8 and analyzed for concentrations of AMH and progesterone. From d 19 to 35, detection of estrus was performed daily and cows detected in estrus were reinseminated. On d 36, bulls were placed with cows for 65 d of natural service breeding. Factors identified to be associated with concentrations of AMH in plasma were breed of the cow and lactation number. Concentrations of AMH were greater for Jerseys, followed by crossbreds, and then Holsteins. Cows on lactations 2 and 3 had greater concentrations of AMH than those on lactations 1 and ≥ 4. Although pregnancy per AI at the timed AI was not associated with concentrations of AMH, cows with low AMH had greater detection of estrus at timed AI, and the latter benefited pregnancy per AI, particularly in cows that had low progesterone at the beginning of the synchronization protocol. Pregnancy loss between gestation d 30 and 65 was greater in cows with low AMH compared with those with intermediate or high AMH. Return to estrus in cows that failed to become pregnant from the timed AI was not associated with AMH, but pregnancy rate in cows bred on estrus (reinsemination + natural service) was associated positively with AMH. In conclusion, breed and lactation number were identified to be associated with concentrations of AMH in plasma. Concentration of AMH was associated positively with maintenance of pregnancy at the first postpartum AI and with pregnancy rate in cows inseminated after detection of spontaneous estrus. Synchronization of ovulation might override positive associations between AMH and fertility.