The effect of type and concentration of the permeable cryoprotectants on the viability of vitrified-warmed ovine blastocysts produced in vitro

This study was designed to optimize the vitrification of domestic animals embryos and achieve the highest survival rates after freezing-thawing pre-implantation embryos, in these animals and then the effect of different concentrations of permeable cryoprotectants such as ethylene glycol (3.6, 4.5 and 5.4 mmol per liter) and glycerol (2.8, 3.4 and 4.2 mmol per liter) in the vitrification medium and the type of cryoprotectant used in equilibration media were studied. In conventional vitrification method in 0.25 ml straws, ovine in vitro produced blastocysts on day 6 were equilibrated in equilibration media containing ethylene glycol or glycerol and then the embryos of each group were transferred to the vitrification solution containing 20, 25 or 30% ethylene glycol and glycerol. Blastocysts survival and hatching rate were recorded after 24 and 72 hours, respectively, after thawing of embryos in each group. In spite of higher permeability and lower toxicity of ethylene glycol compared with other cryoprotectants, a trend of higher survival and developmental rate was obtained in vitrified/warmed blastocysts that equilibrated in medium containing glycerol (P