Preovulatory Follicle Size and Reproductive Parameters in Arabian Mares: A Comprehensive Analysis

While the size of the preovulatory follicle is a crucial marker of reproductive potential in mares, its connection to reproductive parameters, especially in Arabian mares, remains uncertain. This study examined the association between preovulatory follicle size and various reproductive parameters in 301 Arabian mares, monitored ultrasonographically over four years and 563 estrous cycles. The mares were categorized into four age groups: 3–8, 9–13, 14–17, and 18 years and older. The preovulatory follicle diameter across consecutive cycles and the size of follicles leading to pregnancy post-ovulation were analyzed in relation to the ovulation side, age, parity, ovulatory cycle, and parous state. The mean preovulatory follicle size was 46.3±4.34 mm (range: 39–60 mm), with no significant difference between the pregnancy and non-pregnancy cycles (p=0.490). Parity was not correlated with overall follicle size (r=-0.013, p=0.757) or follicle size during the pregnancy cycles (r=-0.060, p=0.303). However, preovulatory follicle diameter varied significantly across ovulatory cycles (p=0.040), with the second cycle having the smallest mean follicle size (45.45±0.35 mm) compared to the first (46.5±0.23 mm) and third (46.95±0.53 mm) cycles. Additionally, parous mares had significantly larger follicles (46.40±0.19 mm) than maiden mares (45.25±0.57 mm, p=0.050), while age group (p=0.796) and ovulation side (p=0.558) had no significant effect on follicle size. Follicle size remained consistent between pregnancy and non-pregnancy cycles across different age groups, consecutive cycles, parity states, and ovulation sides. These findings suggest that although follicle size varies across ovulatory cycles and parous states, it does not significantly affect pregnancy outcomes in Arabian mares. This insight could help refine breeding strategies by emphasizing the role of factors other than follicle size in optimizing reproductive success.