Evaluation of two oestrus synchronization regimens in eFSH-treated donor mares.

The research article investigates the efficacy of two different procedures for synchronizing oestrus, or the period of sexual receptivity in female animals, and increasing ovulation in horses for embryo transfer programs. The study found that while one method resulted in higher synchronization, it also led to fewer ovulations.

Oestrus Synchronization Methods and Experiment Design

• The study’s main objective was comparing two procedures to regulate oestrus and stimulate superovulation in mares. Superovulation is a process used in animal breeding to produce multiple ovulations in a cycle.
• The two procedures compared were a combination of progesterone and estradiol-17β treatment (P&E group), and a prostaglandin F2α application (PG group).
• For the P&E group, the mares received daily doses of progesterone and estradiol-17β for 10 days, with a final dose of prostaglandin F2α on the last day.
• The PG group was treated with prostaglandin F2α 5 days post-ovulation.
• Both groups were also subjected to equine follicle-stimulating hormone treatment and were bred after this. The process of embryo recovery and transfer was done routinely.

Results of the Synchronization Methods

• The interval to ovulation, meaning the time period leading up to when the mares ovulated, was similar for both groups.
• Synchronization success — how well the mares’ cycles matched up — was higher with the P&E regimen.
• However, the P&E regimen resulted in fewer ovulations, constituting a potential disadvantage.
• Both methods had similar results in terms of embryo recovery and recipient pregnancy rates after the embryo transfers.

Conclusion

• The authors concluded that the P&E regimen seems more reliable for oestrus synchronization in mares treated with an equine follicle-stimulating hormone.
• Even though the P&E regimen resulted in fewer ovulations, which could be a disadvantage for programs needing a higher number of embryos, it did not affect the overall recipient pregnancy rate per transferred embryo, as both groups had similar rates.