Abstract
The relationship between thawing rate and the viability of frozen bovine blastocysts derived from in vitro fertilization and culture was examined. Embryos were frozen in straws with 1.4M glycerol+0.2M sucrose(GS), 1.6M 1,2-propanediol(PG) or 1.8M ethylene glycol(EG). They were thawed at various rates by placing the straws in 10, 20, 30, 40 or 50 C water bath. As soon as the crystallized medium in the straw melted, the contents were drained into a petri dish. The embryos were transferred into culture medium and co-cultured with cumulus cells for up to 72 h. When embryos were frozen in GS, there were no significant differences in the proportion of survived embryos which recovered the blastocoel among the various thawing rates, but hatching rate of the embryos increased with increasing the thawing rate. When embryos were frozen in PG, the survival (94%) and hatching rates (77%) of embryos thawed in 20 C water bath (876 C/min) were significantly higher (P<0.05) than those observed in other thawing rates. When embryos were frozen in EG, there were no significant differences in the rates of survival (82∼94%) and development (73∼91%) with all the thawing rates.
