Cryopreservation of In Vitro Matured Buffalo (Bubalus bubalis) Oocytes by Slow Freezing or Vitrification

The present study was conducted to determine the effects on morphology and developmental competence of in vitro matured buffalo oocytes subjected to slow freezing or vitrification. Slaughterhouse-derived buffalo oocytes were matured in vitro and were either cryopreserved by slow freezing with a programmed controlled-rate freezer or were vitrified using conventional 0.25 ml French straws, either sealed (close system) or obliquely-cut straw (open system) using an ethylene glycol-based solution. Cryopreserved buffalo oocytes were evaluated for morphology at post thawing/warming and for subsequent development after fertilization in vitro. The results revealed that the proportions of. morphologically normal oocytes were significantly higher with vitrification procedures than with slow freezing (p<0.01). For vitrification, higher survival rate was achieved with buffalo oocytes vitrified using a close system rather than with the open system. Moreover, vitrification in close system resulted in morula and blastocyst development, albeit low. In conclusion, vitrification was more effective than slow freezing for the cryopreservation of buffalo oocytes matured in vitro.