Pregnancy Rates Following Low-Temperature Storage of Large Equine Embryos Before Vitrification.
Authors: Diaz Fabian A, Gutierrez Emilio J, Cramer Eddie, Paccamonti Dale L, Gentry Glen T, Bondioli Kenneth R
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Cryopreservation of equine embryos through vitrification can achieve good pregnancy rates, yet the technique's limited commercial uptake stems from requiring specialised equipment and technical expertise at centralised facilities—a significant barrier for many breeding operations. Researchers evaluated whether large equine embryos could tolerate brief chilling during transport by collecting 37 Grade 1 embryos on Day 7 or 8 post-ovulation, cooling them to 9–12°C for 0, 12, or 24 hours, then vitrifying and transferring them into recipient mares. Day 7 embryos demonstrated markedly superior viability, with pregnancy rates of 55.5% and 75% following 12 and 24 hours of cooling respectively, whereas Day 8 embryos yielded only 0% and 16.6% under identical conditions; embryo size also proved critical, with specimens smaller than 550 μm achieving 71.4% pregnancy rates compared to just 12.5% for larger embryos. These findings substantially improve the practical feasibility of embryo export, as Day 7 equine embryos up to 550 μm diameter can tolerate 12–24 hours of controlled chilling without compromised fertility outcomes—making it viable to ship embryos from collection sites to specialist cryopreservation centres rather than requiring in-situ vitrification equipment. For practitioners, this expands access to embryo freezing technology by decoupling embryo collection from immediate vitrification, provided attention is given to collection timing and embryo selection criteria.
Read the full abstract on PubMed
Practical Takeaways
- •Day 7 embryos can be safely cooled to 9-12°C for 12-24 hours during transport to specialized centers without compromising viability, reducing need for on-farm micromanipulation equipment
- •Embryo size matters: prioritize embryos smaller than 550 μm for cooling protocols to maximize pregnancy success rates
- •This approach makes commercial embryo cryopreservation more accessible to farms without specialized equipment, potentially increasing industry adoption
Key Findings
- •Day 7 equine embryos cooled for 12-24 hours before vitrification achieved 55.5-75% pregnancy rates, compared to 0-16.6% for Day 8 embryos
- •Embryos <550 μm diameter resulted in 71.4% pregnancy rate versus 12.5% for embryos >550 μm after cooling
- •Low-temperature storage (9-12°C) of large equine embryos for up to 24 hours before vitrification is viable for commercial transport applications