The effect of hormone treatments (hCG and cloprostenol) and season on the incidence of hemorrhagic anovulatory follicles in the mare: a field study.

This study investigates the connection between hormone treatments used for inducing estrus and ovulation in mares and the occurrence of hemorrhagic anovulatory follicles (HAFs). It found that mares treated with a hormone called cloprostenol were more prone to developing HAFs compared to mares with spontaneous cycles or those treated with human chorionic gonadotropin alone.

Understanding the Study

• The research was designed to examine the link between use of hormonal treatments which stimulate estrus (a period of sexual receptivity) and ovulation in mares, and the occurrence of HAFs, which are a type of abnormal follicle that does not rupture on maturity and therefore doesn’t release an egg for fertilization.
• The study was conducted in a commercial breeding clinic across two breeding seasons with a diverse group of mares representing the general mare population.

Findings

• Of the hormonal treatments used, cloprostenol had a more significant connection with the presence of HAFs. The frequency of HAFs was demonstrably higher in mares treated with cloprostenol compared to those having spontaneous cycles or those treated with human chorionic gonadotropin alone.
• There wasn’t any significant effect of the season on the occurrence of HAFs.
• Average time from the advent of cloprostenol treatment to the commencement of HAF development was approximately 6.1 days.

Implications

• The use of cloprostenol for inducing estrus and ovulation may lead to an elevated risk of developing HAFs in mares. This might have implications for fertility treatments and reproductive management in equines.
• The absence of any variation in HAF incidence across the different seasons suggests that environmental factors related to season may not play a major role in the development of such follicular conditions.
• The findings indicate that the age of mares doesn’t significantly impact the incidence of HAFs. Both mares with HAF cycles (average age 12 years) and those with ovulatory cycles (average age 10.5 years) showed comparably similar ages, suggesting that age as an isolating factor may not be directly related to the development of HAFs.