Repeatability of preovulatory follicular diameter and uterine edema pattern in two consecutive cycles in the mare and how they are influenced by ovulation inductors.

This study explores how consistently a mare’s follicular diameter and uterine edema pattern can be repeated in two consecutive breeding cycles and how these might be affected by ovulation induction treatments. The findings show that mares ovulate from similar follicular diameters across two consecutive cycles, with hormonal treatments reducing this diameter. The mares’ uterine edema patterns also showed a certain consistency. Therefore, measurements taken from previous cycles could be reliable indicators of optimal breeding times, especially in mares ovulating from unusually small follicles.

Research Objectives and Methods

• The research sought to evaluate the consistency of preovulatory follicular diameter and uterine edema patterns in two spontaneous cycles in mares. It further aimed to examine how ovulation-inducing treatments influence these two factors.
• Fifty-three mares were observed over the course of two consecutive cycles. During these cycles, the mares were scanned thrice a day from 2 to 3 days leading to ovulation.
• In the first cycle, the mares ovulated naturally without any hormonal intervention. In the subsequent cycle, they received one of four possible treatments: no hormonal treatment, 1500 IU hCG, 125-250 microg Cloprostenol, or 2.1 mg Deslorelin implant.

Main Findings

• Results showed a high consistency in the mares’ follicular diameters across the two spontaneous breeding cycles, indicating that mares tend to ovulate from follicles of similar size in successive cycles.
• The three ovulation-inducing treatments had a significant effect in reducing the preovulatory follicular diameter. This suggests these treatments can influence the follicular size from which mares ovulate.
• A fair degree of correlation was also observed in the patterns of uterine edema across the two cycles, reflecting a degree of repeatability in this physiological aspect of the mares’ reproductive process.

Conclusions and Implications

• The research concludes that mares ovulate from consistent follicular diameters across consecutive cycles. Hence, follicular diameter readings from previous ovulations may provide reliable predictions about the optimal breeding time in future cycles.
• This implies that breeders can significantly boost their breeding success rates by monitoring and recording the follicular diameters of mares during ovulation. This information can then be used as a predictive tool for determining optimal breeding times.
• In particular, attention should be paid to mares ovulating from unusually small follicles, as measurements from their previous cycles can prove especially crucial for predicting optimal breeding times.