The Combination of hCG and GnRH Analog to Hasten Ovulation in Mares Does not Change Luteal Function and Pregnancy Outcome in Embryo Recipient Mares.
Authors: Segabinazzi Lorenzo G T M, Oba Eunice, Alvarenga Marco A
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Combined hCG and GnRH analogue treatment is widely used in equine reproduction to synchronise ovulation, yet evidence supporting synergistic benefits remains limited. Segabinazzi and colleagues investigated whether administering deslorelin acetate (GnRH analogue) alongside hCG produced superior ovulation induction compared to either agent alone, and critically, whether this combination influenced subsequent luteal function and embryo transfer outcomes in recipient mares. Across 17 experimental mares and 194 retrospective embryo transfer cases, the researchers measured corpus luteum diameter, blood flow, and serum progesterone concentrations from ovulation induction through day 16, alongside pregnancy rates and loss data. Despite minor differences in progesterone concentration on the day of ovulation, the combination therapy yielded no measurable advantage over single-agent protocols: corpus luteum development, progesterone dynamics over time, pregnancy establishment rates, and pregnancy retention to 60 days were equivalent across all treatment groups. These findings suggest that the widespread adoption of combined hCG–GnRH protocols may represent unnecessary polypharmacy, with potential implications for cost-effectiveness and medication burden in breeding programmes, though practitioners should continue individualised assessment pending further investigation into specific clinical scenarios.
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Practical Takeaways
- •Using hCG and GnRH analog together to induce ovulation does not provide synergistic benefits over single-agent protocols in recipient mares—consider cost savings by using either agent alone
- •Embryo transfer pregnancy outcomes are not compromised by ovulation induction method; practitioners can select based on individual mare response and drug availability rather than efficacy concerns
- •Luteal function (CL size, blood flow, and progesterone production) develops normally regardless of ovulation induction method, simplifying post-ovulation management protocols
Key Findings
- •Combined hCG and deslorelin acetate did not hasten ovulation more efficiently than either drug alone in mares with ≥35 mm follicles
- •No differences in corpus luteum diameter, blood flow, or progesterone concentration over 16 days post-ovulation between treatment groups
- •Pregnancy rates (5 days post-embryo transfer) and pregnancy loss (up to 60 days) were similar across control, hCG, deslorelin acetate, and combined treatment groups (n=194 transfers)
- •Control group had higher progesterone on the day of ovulation compared to GnRH group (P<0.05), but no other progesterone differences emerged over time