The chestnut, also known as a night eye, is a callosity on the body of a

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

or other

equine Equinae is a subfamily of the family Equidae, which have lived worldwide (except Indonesia and Australia) from the Hemingfordian stage of the Early Miocene (16 million years ago) onwards. They are thought to be a monophyletic grouping.B. J. Ma ...

, found on the inner side of the leg above the knee on the foreleg and, if present, below the

hock Hock may refer to: Common meanings: * Hock (wine), a type of wine * Hock (anatomy), part of an animal's leg * To leave an item with a pawnbroker People: * Hock (surname) * Richard "Hock" Walsh (1948-1999), Canadian blues singer Other uses: * A ...

on the hind leg. It is believed to be a

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

toe, and along with the

ergot Ergot ( ) or ergot fungi refers to a group of fungi of the genus ''Claviceps''. The most prominent member of this group is '' Claviceps purpurea'' ("rye ergot fungus"). This fungus grows on rye and related plants, and produces alkaloids that c ...

form the three toes of some other extinct Equidae. Darren Naish dissents from this belief, noting that the chestnut is "not associated with the metacarpus or metatarsus, the only places where digits occur." Chestnuts vary in size and shape and are sometimes compared to the fingerprints in humans. For purposes of identification some

breed registries A breed registry, also known as a herdbook, studbook or register, in animal husbandry and the hobby of animal fancy, is an official list of animals within a specific breed whose parents are known. Animals are usually registered by their breeder ...

require photographs of them among other individual characteristics. However, because chestnuts grow over time and horse groomers often peel or trim off the outer layers for neatness, their appearance is subject to change.

Distribution among equines

The evolution of the horse involved a reduction in the number of toes to one, along with other changes to the ancestral

equid Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus' ...

foot. The chestnut is thought to correspond to the ''wrist pad'' of dogs and cats, or to be a

scent gland similar to those found in some deer and other animals. chapter 2 The domestic horse is almost alone among

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

equines in having chestnuts on the hind legs. Chestnuts are absent from the hind legs of

ass Ass most commonly refers to: * Buttocks (in informal American English) * Donkey or ass, ''Equus africanus asinus'' **any other member of the subgenus ''Asinus'' Ass or ASS may also refer to: Art and entertainment * ''Ass'' (album), 1973 albu ...

es and

zebra Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. zebr ...

s. The majority of

domestic horse The horse (''Equus ferus caballus'') is a Domestication, domesticated, odd-toed ungulate, one-toed, ungulate, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two Extant taxon, extant subspecies of wild horse, ''Equus fer ...

s have chestnuts on all four legs, as does the

Przewalski's horse Przewalski's horse (, , (Пржевальский ), ) (''Equus ferus przewalskii'' or ''Equus przewalskii''), also called the takhi, Mongolian wild horse or Dzungarian horse, is a rare and endangered horse originally native to the steppes of ...

, but a few

horse breed A horse breed is a selectively bred population of domesticated horses, often with pedigrees recorded in a breed registry. However, the term is sometimes used in a broader sense to define landrace animals of a common phenotype located within a l ...

s are reported to lack chestnuts on the hind legs. These include: *

Banker horse The Banker horse is a breed of feral horse (''Equus ferus caballus'') living on barrier islands in North Carolina's Outer Banks. It is small, hardy, and has a docile temperament. Descended from domesticated Spanish horses and possibly brough ...

(most individuals) *

Caspian pony The Caspian is an Iranian breed of pony or small horse of Oriental type. The breed was created in 1965 by Louise Firouz, an American living in Iran, from a base stock of a small number of small horses found in the Elburz Mountains. In 2011, ...

(some individuals) * Icelandic horse (most individuals)

Grooming

Chestnuts grow over time, protruding from the surface of the leg. Grooming for horse showing may include peeling or trimming the outer layers to give a neater appearance to the leg; they may peel more easily if softened first with

baby oil Baby oil is, in general terms, an inert oil for the purpose of keeping skin soft and supple. It is often used on babies for the purpose of maintaining "baby-soft" skin, but it is also often used by adults for skincare and massage. The skin of an ...

or moisturizer. If left alone, eventually the chestnut peels naturally.

References

External links

Chestnuts And Ergots In Horses
* {{Commons-inline, Chestnut (Horse Anatomy) Horse anatomy

Distribution among equines

Grooming

See also

References

External links