Dzo Dzo A dzo (Tibetan མཛོ་ mdzo) (also spelled zo, zho and dzho) is a hybrid between the yak and domestic cattle. The word dzo technically refers to a male hybrid, while a female is known as a "dzomo" or "zhom". In Mongolian it is called khainag (хайнаг). There is also the English language portmanteau term of yattle, a combination of the words yak and cattle, as well as yakow, a combination of the words yak and cow. Dzomo are fertile (or, fecund) while dzo are sterile. As they are a product of the hybrid genetic phenomenon of heterosis (hybrid vigor),
Wild horse cranial and metacarpal differences, indicates the presence of only two subspecies in postglacial times, the tarpan and Przewalski's horse. At present, the domesticated and wild horses are considered a single species, with the valid scientific name for the horse species being "Equus ferus." The wild tarpan subspecies is "E. f. ferus", Przewalski's horse is "E. f. przewalskii", and the domesticated horse is "E. f. caballus". The rules for the scientific naming of animal species are determined in the International Code of Zoological Nomenclature, which stipulates that the oldest available valid scientific name is used to name the species. Previously, when