| Summary: | Studies to date have shown that wood bison embryo development in vitro is compromised with little or no embryos developing to the blastocyst stage. The aim of this study was to use bison-cattle hybrid embryos, an interspecies that is known to result in live offspring in vivo, as a model for assessing species-specific differences in embryo development in vitro. Cattle oocytes were fertilized with cattle, plains bison and wood bison sperm. Blastocyst development rates were 34.45 ± 2.45% (cattle), 39.56 ± 3.44% (plains bison hybrid), 23.43 ± 1.33% (wood bison hybrid). Plains and wood bison hybrid blastocysts had significantly lower cell numbers than cattle blastocysts (110.1 ± 4.6, 104.2 ± 5.9, 133.3 ± 8.3, respectively; n=10). There was significantly more apoptosis in hybrid wood bison blastocysts than in those of either cattle or hybrid plains bison. As well, ATP levels (n=25) and expression profiles of NRF1, mtTFA and Cytb (n=3, rep=3) were not significantly different among groups in both 8-16 cell and blastocyst stage embryos. These data confirm that wood bison hybrid embryos are incompetent compared to cattle embryos most likely due to media conditions.
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