In vitro development and post-thaw survival of blastocysts derived from delipidated zygotes from domestic cats

The ability to cryopreserve in vitro-produced feline embryos was investigated. To improve the survival rate of cryopreserved embryos, first the developmental ability of in vitro fertilized feline zygotes (after removal of intracellular lipids) was determined, followed by the post-thaw survival of cryopreserved blastocysts derived from delipidated zygotes. More than 67% of the delipidated zygotes cleaved and 36% of them developed to the morula stage. The developmental ability of delipidated zygotes to the blastocyst stage (26%) was similar to that of sham-operated (30.5%) or control embryos (31.3%). Although the survival rate of delipidated blastocysts (81.8%) after freezing and thawing tended to be higher than that of control embryos without delipidation (60.6%), rates were not significantly different between the both groups. In conclusion, in vitro-produced feline blastocysts were successfully frozen, removal of the cytoplasmic lipid content in feline zygotes did not impair their in vitro developmental competence (up to the blastocyst stage), and reduction of cytoplasmic lipids by aspiration had no apparent effects on the survival of in vitro-derived blastocysts after cryopreservation.