EFFECT OF CULTURE SYSTEM ON THE SURVIVAL OF CRYOPRESERVED BOVINE EMBRYOS

This study compares the effect of culture system on the survival and hatching rates of in-vitro produced bovine embryos cryopreserved by slow freezing and vitrification. Oocytes were collected by slicing of ovaries from slaughtered cows. Presumptive zygotes produced by IVM/IVF were randomly allocated to one of the following culture media; TCM-199 or SOF. Day 7 and day 8 blastocysts, cultured in TCM-199 or SOF, were subjected to two cryopreservation methods; slow freezing and vitrification. Development of blastocysts 4, 24 and 48 hours post-thawing and hatching rates were recorded. There were no statistical differences in the post-thawing development or hatching rate between day 7 and day 8 cryopreserved blastocysts cultured in TCM-199 or SOF. But a significant difference was observed in the post-thawing development (4, 24, and 48 hours) of day 7 vitrified blastocysts cultured in SOF (46.1, 67.4, and 70.7%, respectively), as their survival rates were better than that cultured TCM-199. Day 7 and day 8 blastocysts culture in SOF had a better post-thawing development and 48 hours) after slow freezing than those cultured in TCM-199. Slow frozen and vitrified blastocysts cultured in SOF hatched more than the slow frozen ones cultured in TCM-199. In summary, day 7 vitrified blastocysts cultured in SOF were more cryotolerant. Cryopreserved blastocysts that were cultured in SOF survived vitrification and slow freezing better than those cultured in TCM-199.