Equine Embryo Biopsy, Genetic Testing, and Cryopreservation

Abstract

Embryo cryopreservation and embryo biopsy have been slow to become established in equine reproductive practice, partly because of the difficulty in applying these techniques to the equine embryo as it is typically recovered from the uterus, that is, at day 7 after ovulation as an expanded blastocyst. Over the past 5 years, we have developed a technique, using micromanipulation with the Piezo drill, which provides a method for biopsy of both small and large equine embryos, with accurate genetic diagnosis from the biopsied cells and normal pregnancy and foaling rates after transfer. During the development of this biopsy technique, we found that blastocysts collapsed after biopsy showed relatively high viability after vitrification and warming. Modification of vitrification methods allowed the establishment of a vitrification technique that supports normal pregnancy rates for expanded blastocysts up to 650 μm in diameter. This technique uses blastocyst collapse, vitrification medium containing ethylene glycol and galactose, in combination with warming medium containing sucrose, and a low-volume vitrification device. Biopsy and vitrification of expanded equine blastocysts are now offered commercially, and have the potential to become valuable tools for use by the equine practitioner in the efficient management of equine reproduction.