The post-thaw survival of mouse embryos of the various developmental stages was determined after cryopreservation by vitrification in a solution containing ethylene glycol, Ficoll and sucrose (EFS). All the embryos were equilibrated for 2 minutes just prior to freezing. The number of blastomeres during in vitro development was counted by nuclei higher rates of post-thaw survival were obtained from the embryos of 2-cell(92.2%), 8-cell(77.2%) or morula stage(90.0%) than those of blastocyst stage(62.7%). The number of blastomeres per embryo following in vitro culture for 24 hours was significantly(P<0.05) smaller as 66.0f22.3 in vitrified and thawed morulae than fresh morulae(91.712.2).

• 박충생(경상대학교 농과대학 축산학과)
• 곽대오(경상대학교사범대학 과학교육과)
• 박준규(국립종축원)
• 공일근(경상대학교 농과대학 축산학과)
• 정기화(국립종축원)