Hinnies
The hinny, also known as the blunt male or burreño , is the hybrid animal resulting from the cross between a horse (Equus ferus caballus) and a donkey (Equus africanus asinus). The mule is the result of a cross between a mare and a donkey. They are produced in smaller numbers than mules, since it is easier to combine donkeys with mares than vice versa, since getting pregnant in a donkey is more difficult (one in seven donkeys can conceive when covered by a horse).
Features
Hinnies are smaller than mules, and while the mule's face is more reminiscent of a donkey, the hinnie's is more like a horse's, which is long and thin. It does not have ears as long as the mother, although somewhat longer than the father's. Its tail is hairy throughout its entire length like horses. It presents not very slender shapes and its size is close to that of the donkey (Equus africanus asinus). Its size is believed to be restricted by having been gestated by a donkey, whose womb is smaller than that of a mare, which limits the growth of the fetus.
As a hybrid animal, the hinnie is almost always sterile due to the difference in the number of chromosomes in the nucleus (horse, 64; donkey, 62). This means that when they are combined, offspring (mule or hinnies) come out with 63 chromosomes, that is, they do not form pairs; which results in them not dividing equally during meiosis.
Its exterior morphology is similar to that of its father, the horse, and its skeleton to the donkey, its mother. Its size is intermediate between the mule and the donkey; its head is fine, slender, harmonious and well proportioned like that of a horse, with ears of medium length but similar to those of a horse, the orbital arches are prominent: the nose is elastic and very dilatable, and the false nose is diverticulate; the mane on the neck and tail are abundant and long like her father's; the back, the back and the croup or haunch are straight and sharp as donkeys have; the limbs are lean and the hooves appear broader than those of the donkey.
Its genital organs are highly developed, with very developed and long nipples or preputial nipples. The skin is very fine, and the hairy coat is uniform in color, generally dark, and they preserve the dorsal stripe with its crucial tongues and the locks on the fore and hind legs; In addition, it has four spectacles or chestnuts on all four limbs, as on the horse; the donkey has two and the mule has three. (The glasses are horny tissue plates located on the inside of the limbs, on the front limbs above the knees, and on the hind limbs below the hocks.
These formations are supposed to be vestiges of the little finger, the fifth finger of the horses; these are defined after one year of age and are like the fingerprints of humans and are used to identify them.)
Genetic problems of crossbreeding
Hinnies are almost always sterile, and in the few cases of fertility the young tend to be underweight and weak. Its sterility is attributed to the different number of chromosomes of the species from which it comes (donkeys have a nucleus of 62 chromosomes, while those of the horse have 64).
The hinn and the mule are really man-made animals, since in the natural state the two parent species live on different continents. The horse and the donkey have a relatively recent common ancestor, they belong to the same genus, which is why they share more than 97% of their genes, close enough to produce offspring but too far apart to be fertile (something that has been known since ancient times), since the horse has 64 chromosomes while the donkey has 62.
Obtaining hinnies
To obtain mules or hinnies, it is necessary to train or deceive the male with the presence of a female of his species to achieve interspecies copulation or use artificial insemination.
Uncastrated male mules and hinnies often have a high sexual appetite even though they are sterile, because their testicles produce testosterone at normal rates. That is why they are castrated for work.