The interrelationship between antral follicle count, anti-Müllerian hormone concentration, and age in mares

Abstract

Anti-Mullerian hormone (AMH) is a glycoprotein expressed by granulosa cells of small follicles in the equine ovary, and serum AMH concentrations are related to follicular reserve in a number of species. The objectives of this study were to determine: (i) the relationship between serum AMH concentration, antral follicle count (AFC), and age in mares (ii) the association between serum AMH concentration and the number of follicles classified by size (iii) the repeatability of serum AMH concentrations and AFC across estrous cycles as well as (iv) the relationship between AFC and progesterone concentrations. Mares, classified as young (3-8 y, n1⁄410), middle aged (9-18 y, n1⁄416), or old (>18 y, n1⁄419), were examined with transrectal ultrasonography during 3 interovulatory intervals. On day 12 (day 01⁄4 ovulation) of the first, day 6 and 12 of the second, and day 6 of the third estrous cycle, all antral follicles were measured and the number of follicles were classified by size ( 35 mm). Serum AMH and progesterone concentrations were determined by ELISA. A mixed model with mare as a random effect was used in the statistical analysis, and correlations between variables were determined with Spearman’s rank correlation. Antral follicle count was positively associated (P1⁄40.0003) with serum AMH concentration, and the correlation between AFC and AMH concentrations differed by age group with a higher positive correlation in older