Equine researchers at the University of Kentucky (UK) have been chasing anti-Mullerian hormone (AMH, which is produced by cells in fetal testes as well as granulosa cells) for quite some time. They’ve determined they can use it to test for cryptorchidism in male horses as well as ovarian tumors in mares. Now, they’re trying to see if the hormone can predict an aging mare’s remaining follicle count.

Barry Ball, DVM, PhD, Dipl. ACT, Albert G. Clay Endowed Chair in Equine Reproduction at UK’s Maxwell H. Gluck Equine Research Center, in Lexington, presented his group’s results in this area at the 2014 American Association of Equine Practitioners Convention, held Dec. 6-10 in Salt Lake City, Utah.

"Mare fertility declines with age in association with reduced follicle count," Ball explained. In other species, such as cattle and mice, "AMH is highly correlated with antral follicle count (AFC, or the total number of follicles that can be counted on ultrasound)."

He hypothesized that AMH concentrations might help predict an aging mare’s AFC, reproductive longevity, and fertility.

In the study, Ball and his colleagues looked at the relationship between AMH, AFC, and follicle reserve in mares of different age groups. They examined 10 young (3-8 years), 16 middle-aged (9-18 years), and 19 older (over 18) mares using transrectal ultrasound and ELISA tests. In their results they found a strong relationship between AMH and AFC in older mares but not in young ones. They also discovered that mares with lower AMH concentrations had smaller follicles.

Additionally, Ball said they found that AMH