Improved vitrification method allowing direct transfer of goat embryos

The aim of this study was to design a vitrification method suited to field embryo transfer experiments in goat. In a first experiment, a standard vitrification protocol, previously designed for sheep embryos was compared to slow freezing of goat embryos. No significant difference was observed on kidding rate (48% versus 69%, respectively), nor on embryo survival rate (35% versus 45%). Second experiment: all embryos were vitrified. After warming, embryos were either transferred directly (direct transfer), or after in vitro dilution of the cryoprotectants (conventional transfer). The kidding rate was not affected by the transfer method (38% versus 23%, respectively). However, embryo survival rate tended to be higher after direct transfer (26% versus 14%). Third experiment: OPS vitrification was compared to standard vitrification. The kidding rate was not affected (22% versus 39%, respectively), but the embryo survival rate was lower after OPS (14% versus 28%). Fourth experiment: 0.4 M sucrose was added with cryoprotectants in vitrification. The kidding rate after direct transfer was significantly enhanced after addition of sucrose (56% versus 27%, respectively), whereas embryo survival rate was not significantly affected (32% versus 18%). Fifth experiment: vitrification with sucrose supplementation was compared to slow freezing. No significant difference was observed after direct transfer on kidding rate (52% versus 31%, respectively), but embryo survival rate tended to be higher after vitrification (34% versus 21%). In conclusion, our results indicate that addition of 0.4 M sucrose in association with direct transfer improves significantly the viability of goat vitrified embryos.