Anti-Müllerian hormone levels in relation to ovarian structures, season and age in Lipizzaner broodmares.

The anti-Müllerian hormone (AMH) is a granulosa cell-derived hormone that has been associated with female fertility and reflects the population of growing follicles. This study aimed to evaluate the average concentration of AMH in Lipizzaner mares, as well as to determine the relationship between AMH concentration and follicle number and size. We also investigated the relationship between the age of mares and their AMH levels. The possible effect of seasonality of AMH levels was also assessed. Twenty-three mares between 6 and 24 years of age were included in the experiment. Mares were divided into two groups: Group 1 included mares aged 6 - 15 years (n = 11), while Group 2 included individuals older than 15 years of age (n = 12). Venous blood was collected and ovarian activity was monitored parallelly by transrectal ultrasonography. Serum AMH concentrations varied widely between the two different groups. AMH concentrations were significantly lower in old mares than in younger animals. A positive relationship was detected between AMH concentration and the number of medium-sized follicles (P = 0.022), large follicles (P = 0.016) and the total follicle count (P = 0.026). No seasonal effect was detected.