EN
Cryopreservation is not a routine procedure for the storage of equine embryos. Regardless of the method of cryopreservation, its efficiency in the transplantation of frozen embryos is relatively low. The success of freezing depends on the phase of embryo development, the type and concentration of the cryoprotectant and the freezing method. Equine embryos can be successfully cryopreserved by using conventional, slow-cooling methods or by vitrification, when embryos do not exceed 250 µm in diameter. In bigger equine embryos, changes in tolerance to cryopreservation are observed. These failures may result from the glycoprotein capsule, which appears in later stages of embryo development. New methods of vitrifying embryos in a reduced volume of fluid (2-10 µl) enable embryos to pass quickly through the critical stage of rapid temperature changes and make it possible to lower the concentration of cryoprotectants in the vitrification mixture. Vitrification is a rapid procedure that requires limited equipment and time. Further research is needed to increase the survival of equine embryos after slow-freezing or vitrification.