Cryopreservation of Equine Embryos and First Report of a Native Colombian Breed Born by Transfer of an Equine Vitrified Embryo

Abstract

The aim of this paper is to report on the success of a cryopreservation procedure of equine embryos to achieve a viable pregnancy. Equine embryos were collected on day 6-6.5 (<300 μm, n = 24) and subjected to two cryopreservation techniques: group 1 (n = 12), vitrified, exposing them to a VS1 (Gli [1.4 M]) 5 min, VS2 (Gli [1.4 M] + EG [3.6 M]) and VS3 (Gli [3.4M] + EG [4.6 M] 1 min solution. They were packed in 0.25 ml straws and immersed in liquid nitrogen; group 2 (n = 12), slow freezing: exposed to a freezing solution (1.8 M EG + 0.1 M sucrose) for 10 minutes, packed into 0.25 ml straws, brought to the embryos freezer, exposed to a freezing curve and immersed in liquid nitrogen. Following defrosting, cryoprotectants were removed from the 24 embryos in one step; they were submerged in culture medium DMEM/F12 + 10% of fetal bovine serum (FBS) and incubated under controlled atmosphere (5% CO₂, 5% N₂, 90% O₂) for 48 h. Embryonic development was evaluated in 75% of the vitrified embryos (n = 4); 20% of the embryos were subjected to slow freezing (n = 1). No significant difference was observed in the groups regarding embryonic development, but a greater survival tendency on the vitrified embryos was noted. Also, one of these vitrified embryos was transferred to a receiver, achieving a viable pregnancy and the birth of a living foal.