Use of a low dose of equine purified FSH to induce multiple ovulations in mares.

The research explored the effects of a low dose of equine purified FSH (eFSH) on the rate of multiple ovulations and embryo recovery in mares, suggesting its potential as a tool to increase the efficiency of commercial equine embryo transfer programs.

Research Setting and Subjects

• The study was conducted during the physiological breeding season in Brazil and involved 14 Mangalarga Marchador donor mares. These animals participated in a crossover study.
• The research also incorporated another 25 mares of the same breed, aged between 3 and 12 years old. These mares were used as recipients for the embryo transfers.

Methodology

• The mares were closely observed during two consecutive oestrus cycles: an untreated cycle and a subsequent cycle where eFSH was introduced.
• Following an embryo collection attempt on day 8 post-ovulation, the mares were administered 7.5 mg of dinoprost and their two largest follicles were checked every day by ultrasound until they ovulated.
• Upon the identification of a 35-mm follicle, the mares were inseminated every 48 hours with fresh semen from a single stallion, continuing until ovulation.
• Ovulations were induced via intravenous administration of 2.500 IU of human chorionic gonadotropin when a follicle of 35-40 mm was detected.
• In the eFSH treated cycle, 5 mg of eFSH was administered intramuscularly daily from day 8 post the previous ovulation until at least one follicle reached 35 mm in diameter.
• On the 8th day of the mare’s dioestrus period (where day 0 = ovulation), embryo flushes were performed.

Findings

• Application of eFSH resulted in a higher ovulation rate and occurrence of multiple ovulations than in the control cycle (1.6 versus 1.0 and 50% versus 0%, respectively). One mare even had triple ovulation.
• However, the rates of embryo recovery in control and eFSH treated cycles were nearly identical (0.8 and 1.0 respectively, p > 0.05).
• The rate of pregnancy in the recipient mares following the embryo transfer was similar in both the control and eFSH cycles (11/11 and 10/14, respectively).

Conclusion

• The research concluded that while the use of eFSH enhanced the ovulation rate and caused multiple ovulations, it did not significantly impact the embryo recovery rates or eventual pregnancy rate.
• The authors propose that further studies are required to devise a low-dose eFSH protocol that can consistently boost the efficiency of commercial equine embryo transfer programs.