Deep freezing of horse embryos

Abstract

Fourteen horse embryos recovered non-surgically on Days 6-8 after ovulation (Day 0) were cooled slowly to -35°C (7 embryos) or -40°C (7 embryos) and stored in liquid nitrogen (-196°C) for 4-98 days. Surgical transfer of the thawed embryos to unmated recipient mares that had ovulated -2 to +1 days with respect to the embryo donors resulted initially in the establishment of 4 conceptuses. However, only one mare maintained her pregnancy to term.