IN VITRO EVALUATION AND PREGNANCY RATES AFTER VITRIFICATION OF IN VITRO PRODUCED BOVINE EMBRYOS

The efficacy of different vitrification solutions to cryopreserve in vitro-produced bovine blastocysts was evaluated based on in vitro development of embryos in culture and on in vivo development of embryos transferred into recipients. In the first experiment, 2 vitrification solutions were compared: propylene glycol + glycerol (Pg+Gly) and ethylene glycol + Ficoll + sucrose (EFS). Differences in the overall development and hatching rates in favor of EFS were found (56.4 vs 33.3% and 35.4 vs 13.3 %; P<0.05). In the second experiment, 3 vitrification solutions were compared: EFS, modified EFS (EFSm) and ethylene glycol + glycerol (Eg+Gly). The vitrification solutions EFSm and Eg+Gly yield higher hatching rates than did EFS (57.7 vs 59.6 vs 35.7%; P<0.05). The last experiment was designed to compare in vivo 2 vitrification solutions: EFSm and Eg+Gly. There were no differences between them based on the results obtained after transfer (35.2 vs 43.7%). The vitrification solutions EFSm and Eg+Gly have resulted in good pregnancy rates. These results demonstrated that vitrification can be used successfully in the cryopreservation of in-vitro produced bovine embryos, and it might be considered for use in commercial programs.