Superovulation, embryo recovery, and pregnancy rates from seasonally anovulatory donor mares treated with recombinant equine FSH (reFSH).

The research article discusses an experiment involving the use of recombinant equine Follicle-Stimulating Hormone (reFSH) to stimulate follicular growth, multiple ovulations, and embryo production in mares that are seasonally anovulatory (not ovulating). The results show that treatment with reFSH was successful and led to follicular development, ovulation of fertile oocytes, and the production of viable embryos, with comparable effectiveness using once-daily and twice-daily dosage regimens.

Methodology

• Forty mares were randomly divided into four groups, each with a different hormonal treatment regimen. The treatment was given until a follicle of 35mm was observed or for a total period of 10 days.
• When the largest follicle reached 35mm or larger, the treatment was stopped. 2500 IU hCG was then administered via intravenous injection.
• The mares were inseminated with fresh semen repeatedly until ovulation was detected. Alternatively, one dose of frozen semen was used after the detection of the first ovulation.

Embryo Recovery and Transfer

• Eight days after the first ovulation, non-invasive transcervical embryo recovery was undertaken.
• The recovered embryos were transferred to anovulatory mares treated with estrogen and progesterone. These mares were then checked for pregnancy using ultrasonography at periodic intervals.

Results

• All mares receiving reFSH treatment, but none in the saline control group, showed follicular growth. On average, 6.5 days of reFSH treatment were required to develop follicles of ovulatory size.
• Ovulations were detected in 80% of mares in Group 1 and 2, 50% of mares in Group 3, and none in Group 4 (control group).
• Among the ovulating mares, no differences were observed in the number of ovulations, number of embryos recovered, or pregnancy rates across different reFSH treatments.
• Regarding embryo recovery, on average for each ovulated mare it was 88%, and for each ovulation, it was 43%.

Conclusion

• The study demonstrated that reFSH treatment during anestrus effectively results in follicular development, ovulation of fertile oocytes, and the production of embryos that can establish viable pregnancies after transfer.
• Furthermore, the research established that using reFSH once daily was as effective as twice-daily administrations, simplifying the administration regimen.