Mare and stallion effects on blastocyst production in a commercial equine ovum pick-up–intracytoplasmic sperm injection program
Authors: Cuervo-Arango Juan, Claes Anthony N., Stout Tom A. E.
Journal: Reproduction, Fertility and Development
Summary
# Editorial Summary Within commercial equine assisted reproductive programmes, success with ovum pick-up and intracytoplasmic sperm injection (OPU-ICSI) varies substantially between individual animals, yet predicting outcomes remains challenging for practitioners planning treatments. Cuervo-Arango and colleagues analysed 552 OPU procedures across 323 warmblood mares over two years, stratifying results by mare and stallion identity to identify which factors most reliably forecast embryo production. Early performance proved highly predictive: mares producing at least one blastocyst on their first OPU-ICSI cycle had a 77% success rate on subsequent attempts, whereas those failing initially showed a 62% failure rate thereafter. The number of oocytes recovered per session emerged as the strongest predictor of overall success (P < 0.001), with mares undergoing four or more cycles averaging 20.5% blastocyst conversion rates and 1.67 embryos per session, though individual variation was considerable (1.4–46.7% and 0.2–4.2 respectively). Whilst stallion effects existed, they were comparatively modest and consistent across most animals; mare identity and oocyte yield therefore warrant primary focus when counselling clients on realistic treatment expectations and optimising protocol decisions in commercial OPU-ICSI programmes.
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Practical Takeaways
- •If a mare produces blastocysts in her first OPU cycle, continuing the program is statistically justified; conversely, first-cycle failure suggests 62% chance of repeated failure and warrants careful case evaluation before additional attempts
- •The number of oocytes recovered during aspiration is the single most important practical indicator of likely success—focus breeding soundness exam and pre-OPU management on maximizing follicle availability rather than selecting young mares, as age alone does not predict outcome
- •Stallion choice has less impact on blastocyst production than mare factors; most stallions cluster in the 15–27% range, so mare quality and responsiveness to OPU is the limiting factor in commercial programs
Key Findings
- •Mares with successful first OPU-ICSI cycle had 77% likelihood of success in subsequent attempts, while 62% failure rate occurred when first cycle yielded no blastocyst
- •Among mares with ≥4 OPU sessions, mean blastocyst production was 20.5% per injected oocyte (range 1.4–46.7%)
- •Number of recovered oocytes per OPU was the strongest predictor of success (P<0.001), with stallion effects less variable than mare effects
- •Mare identity proved more reliable than age as a predictor of OPU-ICSI success