* Gemsbok (Oryx gazella) are antelopes, mammals belonging to the Bovidae family.
* Horses (Equus caballus) belong to the Equidae family.
Different species cannot interbreed. The genetic differences between them are too significant for their offspring to be viable. Even if they were to produce an embryo, it would not survive.
Therefore, the idea of a gemsbok-horse hybrid is purely fictional.