The influence of age, antral follicle count and diestrous ovulations on estrous cycle characteristics of mares.

This research explores how age, follicle count and ovulations in the non-estrous period can impact a mare’s reproductive cycle. It found that as mares age, changes in their follicular parameters, influenced by antral follicle count, contribute to their reproductive aging process. Additionally, ovulations that occur outside of the normal estrous cycle can significantly influence various parameters of the estrous cycle.

Objective and Methodology

• This study aimed to understand the reproductive ageing in mares and to provide insights into predicting their reproductive lifespan.
• The researchers focused on studying the impact of age-induced changes in follicular dynamics, endocrine profiles and primordial follicle counts.
• They also sought to understand the influence of antral follicle count on these age-related changes.
• Lastly, they examined the effect diestrous ovulations have on the estrous cycle.
• Mares of varying ages (young, middle-aged, and old) were observed over two consecutive estrous cycles using transrectal ultrasonography.
• Progesterone and FSH concentrations in their blood were measured to evaluate endocrine profiles.

Key Findings

• The study found that with increasing age, the period between ovulations and the follicular phases becomes longer.
• Older mares also tend to have smaller ovulating follicles.
• However, age did not influence the speed of follicular growth, the number of ovulations, or the length of the luteal phase (post-ovulation period).
• The number of primordial follicles decreased with age, and this could vary significantly between mares of the same age.
• Progesterone concentrations increased with age, but FSH concentrations remained unchanged. However, FSH concentrations seemed to increase during the follicular phase in older mares.
• Mares with a lower count of antral follicles had longer periods between ovulations and longer follicular phases as their age increased.
• Non-estrous cycle ovulations lead to longer periods between ovulations, follicular and luteal phases.

Conclusion

• The researchers concluded that the ageing in mares is closely tied to changes in follicular parameters, which the study suggests is linked to the antral follicle count or ovarian reserve.
• By determining the antral follicle counts in aged mares, a better understanding of their reproductive aging process can be achieved.
• Diestrous ovulations also considerably influence different parameters of the estrous cycle.