Influence of the method of vitrification and developmental stages of embryos on cryopreservation efficiency of in vitrobovine embryos produced in Vietnam

The study aimed to evaluate the influence of different vitrification methods and developmental stages of bovine embryos produced in vitro during cryopreservation in Vietnam. In vitro bovine embryos were frozen by two methods: (1) Vitrification by cryotop and (2) Vitrification by microdrop. The percentage of embryos obtained after thawing of method (1) was higher than that of (2) (100 vs 81.01%, p<0.05). However, there was no difference in survival, re-expansion and hatching blastocyst rates after thawing between the two methods (1) and (2) (88.43 vs 91.89%; 83.1 vs 84.43%; and 20.34 vs 17.79%, p>0.05; respectively). In this study, the survival, cleavage, blastocyst and hatching blastocyst rates of in vitro bovine zygotes after thawing were 86.83, 63.83, 21.39, and 3.91%, respectively. The authors did not observe any difference in survival and hatching blastocyst rates after thawing while vitrification at morula/compact morula and blastocyst stages (82.67 vs 88.43%, 16.54 vs 20.34%, p>0.05; respectively). The results showed that in vitro bovine embryos were successfully frozen at the zygotes, the morula/compact morula and blastocyst stage by vitrification.