THE RESISTANCE OF OOCYTES AND IN VITRO PRODUCED CATTLE EMBRYOS TO CRYOPRESERVATION

In vitro fertilization and production of bovine embryos in vitro is method, which improves utilization of animal reproduction potential. In connection with cryopreservation methods and ability of long-term cryostorage of embryos offers suitable tool for positive influence of endangered species or breeds. In vitro embryo production with subsequent embryo transfer contributes to the improvement of reproduction rates and bypassing some reproduction failure in high productive animal breeding. The method is generally used for in vitro production of transferable bovine embryos. Worldwide about 411 000 of IVP bovine embryos are annually transferred to recipients (IETS, 2013). Most of them were transferred immediately after producing, which is difficult for organization and synchronization of animals. In contrast to this possibility the storage of embryos for later using brings undisputable advantages. In order to protect animal genetic resources and to preserve the gene pool of rare and endangered animals, it is necessary to establish gene banks containing stocks of gametes and embryos of these animals. Optimization of the methods of in vitro production of bovine embryos and increasing their resistance to cryopreservation process is an actual challenge to ensure long-term storage in the gene bank of animal resources. The main goal of this mini-review is to provide general insight into the task of oocyte and embryo resistance to cryopreservation.