Equid hybrids, also called hybrid equines, are created from the crossing of members from the horse family such as a horse, donkey and zebra.
History
From the 20th century on, equid hybrids were being created, though breeding for mules and hinnies had been going on since ancient times. The first crossbreeding was with zebras and donkeys. Equid hybrids can be traced back to Africa where there are vast amount of equid species which resulted in natural crossing, creating hybrid species. These hybrids were found to be more efficient than the original species because they possess certain traits of both species, so scientists began to experiment by crossing other species of horse family and categorizing them as equid hybrids. Equid hybrids are now bred commercially. Mules bred from mammoth studs and stock or draft mares can be as large as 17 hands and are as strong as a normal horse. Other mules are bred for pets or for entertainment such as zoos; these are the miniature horses or miniature donkeys.
Nomenclature
Hybrids are named based on the sex and species of the parents. Hybrids are typically given a portmanteau name, combining the first half of the father’s name and the second half of the mother's name. For example, the cross between a male zebra and a female horse is a zorse. Horse-donkey crosses are an exception to this naming convention. A mule is the cross between female horse and male donkey. A hinny is the cross of male horse and female donkey; mules and hinnies are reciprocal hybrids.
Zebras are usually wild animals, but when they are raised with other domestic horses, they are tame enough to be ridden draught. Mules are smaller, more resistant to heat and exhaustion and much stronger. Horses are much larger, but likely to suffer from exhaustion and heat.
Male mules are sterile, but fertile female mules sometimes occur. The different number and different structure in chromosomes makes it difficult for them to pair up. Donkeys have 62 chromosomes and horses have 64, so their hybrids have 63. Zebras have between 32 and 46 and their hybrids are sterile and infertile. It is harder to cross species if the female has less chromosomes than the males, as in the crossing of a stallion and a jenny ; this results in minimal breeding of hinnies.
Why are mules preferred?
Mules are preferred because they are more tolerant to heat than horses. Horses are more efficient in cold weather and mules, like donkeys, are more effective in deserts. Horses are more likely to suffer from exhaustion when compared to mules. Since mules are relatively slower than horses, they are much safer to ride than horses. It is cheaper to rear mules than horses because they consume less food. Lastly, mules are more enduring than horses and can live longer.
