Equine reproduction researchers know that a specialized embryo freezing process called vitrification results in higher mare pregnancy rates than traditional slow-cooling cryopreservation techniques. But not every veterinarian has access to the specialized vitrification equipment, so they must opt for the less successful approach or ship embryos be vitrified elsewhere. Handling these tiny vulnerable structures with care becomes an issue in the meantime, so researchers at Louisiana State University (LSU) took a closer look at the best approach.

“When large embryos are subject to slow-cooling cryopreservation, pregnancy rates are less than 30%,” said Fabian A. Diaz, MS, a graduate assistant at LSU’s School of Animal Science. “Embryos frozen via embryo micromanipulation and vitrification, however, result in pregnancy rates greater than or equal to 65%.”

So, in an effort to make this preferred method more available to the masses, he examined the toll of temporarily cooling blastocysts to low temperatures (7-10°C, or 44-50°F) before vitrification on pregnancy rates. He described his study results at the 2015 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas.

Embryo transfer involves breeding a mare, whether through live cover or artificial insemination, collecting the embryo approximately six to eight days later, and then transferring the young embryo—called a blastocyst—to a recipient mare for gestation. Alternatively, mare owners can have collected embryos frozen for use until a recipient mare is ready for implantation or simply to preserve them for future implantation.<