Direct Transfer of Frozen-Thawed Bovine Embryos Freezed by Using Ethlene Glycol as a Cryoprotectant

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Bovine embryos (blastocysts) recovered from donor uteri were used in this experiment. The embryos were equilibrated with 1.8M ethylene glycol for 30-60 min in modified phosphate buffered saline (m-PBS) supplemented with 20% calf serum. Embryos were loaded into 0.25-ml plastic straws in a small volume of freezing medium separated by two air bubbles from the same medium filling the rest of the straw. The straws were placed directly into a cooling chumber kept at 0°C and then cooled to -7°C at 1°C/min. After leaving for 15 min at this temperature, including seeding, the straws were then cooled to -30°C at 0.3°C/min. The straws were then left for 10 min at this temperature before being plunged into liquid nitrogen.<BR>The straws confining embryos were thawded at 30-35°C and the embryos were co-cultured with granulosa cell for 48h. Eighty-nine percent (8/9) of embryos developed to hatching blastocyst or hatched blastocyst.<BR>When the frozen-thawed embryos were directly transfered into cow uteri, seventy-three percent (13/18) of recipients became pregnant.<BR>The results of this study demonstrate the potential for using ethylene glycol as a Cryoprotectant for bovine embryos, thus permitting direct transfer of frozen-thawed embryos to recipient cows.
日本暖地畜産学会の論文