In vitro production of interspecies hybrid embryos of cattle (Bos taurus) and wisent (Bison bonasus)

European bison or wisent ( Bison bonasus ) is a rare species that is endangered. The technology for producing in vitro embryos using oocytes of cows and wisent semen can be an effective tool for conservation of genetic resources of this species and their rational use in basic research on the physiology of development and to create the new animals’ types. However, the methods for production of in vitro embryos using the above-mentioned germ cells are currently not described in the literature. In this work, we first attempted to obtain the hybrid cow-wisent embryos in vitro using the IVM/IVF/IVC protocol, developed for domestic cattle ( Bos taurus ). Frozen epididymal sperm derived from wisent was thawed and prepared by the swim-up procedure. Matured oocytes were co-incubated during 18 h together with prepared sperm in Fert-Talp medium, which was replaced then by embrional medium where the embryos were cultured until the blastocyst state. Additionally, for positive control, a part of matured bovine oocytes were fertilized with frozen/thawed ejaculated bull sperm. Fertilizing capacity of male cells of both species was assessed according to the nature of spermatozoa-egg interactions, as well as the capacity of fertilized bovine oocytes to subsequent embryonic development. It was found that the rate of oocytes with sing polyspermy was higher for fertilization with wisent sperm comparing to allogenic insemination (21.6 vs. 8.5 %, P < 0.05). There were no differences between two types of fertilizations nether for the sperm penetration rate (90.0±0.3 vs. 93.3±1.7 % for bull and wisent, respectively), nor for the rate of normal fertilization (78.3±1.7 % vs. 73.2±2.3 %). The similar cleavage and blastocyst formation rates were observed for two fertilization types. Our data indicate the similarity in the mechanisms of oocyte activation and embryonic development in cow and wisent females. In addition, it is obvious that IVM/IVF/IVP protocol, in general, allows in vitro producing cattle-wisent hybrid embryos, however, high levels of polyspermy observed in heterogeneous fertilization, indicates the necessity to adjust the method.