Maximum survival of frozen goat embryos is attained at the expanded, hatching and hatched blastocyst stages of development

Abstract

Embryos were collected 5, 6 and 7 days after ovulation to determine their optimum stage of development for cryopreservation. The embryos were frozen using either glycerol or dimethyl sulfoxide (DMSO) as cryoprotectant, and then thawed and cultured to determine their viability. The rate of survival increased as the stage of development of the embryos increased. All hatched blastocysts survived freezing regardless of which cryoprotectant was used, whereas none of the 22 morulae frozen with DMSO survived, and only 12 of the 63 morulae frozen with glycerol survived. At the early blastocyst stage there was a significantly different result between freezing procedures (P less than 0.05) with greater survival rates obtained using DMSO rather than glycerol. The viability of goat embryos obtained at the early to hatched blastocyst stages, when collected 7 days after ovulation, was assessed by transferring half the embryos singly to recipients and freezing the remainder before transfer. When pregnancy was tested at the 7th week of gestation, the survival rate of fresh embryos was 67/111 (60%) compared with 64/109 (59%) for frozen-thawed embryos.