Abstract
We examined the efficacy of methyl cellosolve (MC) as a cryoprotectant for cryopreservation of bovine embryos derived from in vivo and in vitro. In the presence of 1.3M-MC, in vitro fertilized (IVF) embryos were cooled from 0 C to -6 C at -1 C/min and seeded, held for 10 min, and then cooled either at -0.3 C/min or at -0.5 C/min to -30 C. They were plunged and stored in liquid nitrogen. While no significant difference in the survival rates after 48 h of post-thaw culture was observed beween the 2 cooling rates, the development rates to hatched blastocysts were significantly (P<0.01) higher in cooling at a rate of -0.3 C/min than at a rate of -0.5 C/min. When IVF embryos were cryopreserved in the presence of various concentration of MC or ethylene glycol (EG), the survival and the development rates to hatched blastocysts were higher in 1.3M -MC and 1.8M-EG than in other concentrations of the each cryoprotectant. Sixty one of in vivo embryos collected from 10 superovulated Japanese Black cows and 48 of blastocysts produced in vitro were cryopreserved in the presence of 1.3M-MC or 1.8M -EG, and transferred immediately after thawing into synchronized recipients without removing the cryoprotectant. The pregnancy rates originated from in vivo and in vitro embryos were 48.3% (14/29), 47.6% (10/21) using 1.3M-MC and 50.0% (16/32), 63.0% (17/27) using 1.8M-EG, respectively. These results indicated that MC has the efficacy as a cryoprotectant for direct transfer of bovine embryos.
