In vivo and in vitro survival of goat embryos after freezing with ethylene glycol or glycerol

The aim of the present study was to compare the survival rates of goat morulae and blastocysts after different freezing procedures. The viability of frozen-thawed embryos was assessed both in vivo and in vitro. Two cryoprotectants, ethylene glycol and glycerol, were used and three cryoprotectant removal procedures were compared: progressive dilution in 1.0, 0.5, 0.3 and 0 M of cryoprotectant in PBS; a similar progressive dilution with cryoprotectant in PBS plus 0.25 M of sucrose; or one-step transfer in PBS containing 0.25 M of sucrose. In vitro development of frozen-thawed blastocysts was always higher than that of frozen morulae irrespective of the cryoprotectant (52 129 = 40.3% vs 23 161 = 14.3% ; P< 0.001). In vivo, however, frozen-thawed morulae developed equally as well as blastocysts after an identical freezing-thawing protocol. Development both in vivo and in vitro showed ethylene glycol to be a better cryoprotectant than glycerol for goat embryos at both developmental stages (23 vs 0%, 45 vs 35% in vitro; 34.5 vs 21%, 35 vs 23% in vivo for morulae and blastocysts, respectively).