Reproductive isolation from a cross between a horse and a donkey or between a mare and a donkey, respectively. These animals are nearly always sterile due to the difference in the number of chromosomes between the two parent species. Both horses and donkeys belong to the genus "Equus", but "Equus caballus" has 64 chromosomes, while "Equus asinus" only has 62. A cross will produce offspring (mule or hinny) with 63 chromosomes, that will not form pairs, which means that they do not divide in a balanced manner during meiosis. In the wild, the horses and donkeys ignore each other and do not
Equus (magazine) Equus (magazine) Equus is a monthly magazine for horse owners that was first published in November 1977. The intent of the magazine is succinctly stated by founding editor and publisher Ami Shinitzky's original working title: "The Horseman's Veterinary Journal". In the editorial in the first issue Shinitzky wrote, "EQUUS serves as a bridge between the veterinarian and the horse owner, bringing to our readers the expertise of the nation's leading authorities on the care and maintenance of the animal through the talents of writers who are able to translate often technical information into a language easily understood and rapidly absorbed."