Vitrification of in vitro produced bovine embryos: in vitro and in vivo evaluations

The efficacy of different vitrification solutions to cryopreserve in vitro produced bovine blastocysts was evaluated based upon in vitro development of embryos in culture and on in vivo development of embryos transferred into recipients. In the first experiment, ethylene glycol + glycerol (Eg + Gly) + different sucrose concentrations were evaluated. There were no significant differences in development rates among solutions. As for hatching, the Eg + Gly + 0.1 M sucrose group had a greater rate as compared with Eg + Gly + 0 M sucrose and Eg + Gly + 0.5 M sucrose groups in the evaluations of Day 6, Day 7 and Day 6 + Day 7 embryos; and, Eg + Gly + 0.3 M sucrose group had a greater rate as compared with the Eg + Gly + 0 M sucrose and Eg + Gly + 0.5 M sucrose groups in evaluations of Day 6 and Day 6 + Day 7 embryos. There were no significant differences in development and hatching rates between Day 6 and 7 in in vitro produced bovine embryos within each treatment group. There were significant differences in nuclei number after vitrification between Eg + Gly + 0.1 M and Eg + Gly + 0 M sucrose groups and the Eg + Gly + 0.5 M sucrose group. Pregnancy after 60 days of transfer and calving rates showed a difference between in vivo produced embryos freshly transferred and in vitro produced embryos vitrified with Eg + Gly + 0.3 M. There were no significant differences in gestation length and sex ratio between treatments. As for birth weight, there were significant differences between fresh in vivo produced embryos and all treatments of in vitro produced embryos. There were significant differences in dystocial parturition between in vivo produced embryos and all treatments with in vitro produced embryos. These results demonstrate that vitrification can be used successfully in the cryopreservation of in vitro produced bovine embryos, and that it might be considered for use in commercial programs.