Equine coat color

Horses exhibit a diverse array of coat colors and distinctive markings. A specialized vocabulary has evolved to describe them. Color is one of the first things that is noticed about a horse. Often, a horse is first described by its coat color rather than by breed or by sex.

While most horses remain the same color throughout life, a few, over the course of several years, will develop a different coat color from that with which they were born. Most white markings are present at birth, and the underlying skin color of a horse does not change, absent disease.

The basic outline of equine coat color genetics has largely been resolved, and DNA tests to determine the likelihood that a horse will have offspring of a given color have been developed for some colors. Discussion, research, and even controversy continues about some of the details, particularly those surrounding spotting patterns, color sub-shades such as "sooty" or "flaxen," and markings.

Basic coat colors

Genetically, all horses start out as either chestnut, called "red" by geneticists, represented by the absence of the extension gene ("e"); or "black," based on the presence of the extension gene ("E"). From this initial set of genes, all other color genes act upon the basic set. When at least one copy of another gene is present as a dominant allele, this creates the vast range of colors that horses can possess.

The most common horse colors are:

*Bay: Body color ranges from a light reddish-brown to very dark brown with "black points." (Points refer to the mane, tail, and lower legs). The main color variations are:
**Dark bay: very dark red or brown hair, also called "black bay," "mahogany bay," or "brown."
**Blood bay: bright red hair, the shade variation often considered simply "bay."
**Light bay: lighter than a blood bay, but hairs still clearly more red than gold
*Brown: See Bay, above. All "brown" horses are either genetically bay if they carry the "E" gene or genetically chestnut if they do not. Absent DNA testing, this is usually determined by looking closely at the mane, tail and legs for the presence of black points.
*Chestnut: A reddish body color with no black. Mane and tail is the same shade or lighter than the body coat. The main color variations are:
**Liver chestnut: dark very dark brown coat. Sometimes a liver chestnut is also simply called "brown."
**Sorrel: Reddish-tan to red coat, about the color of a new penny. The most common shade of chestnut.
**Blond or light chestnut: seldom-used term for lighter tan coat with pale mane and tail that is not quite a dun.
*Gray: A horse with black skin and white or mixed dark and white hairs. Gray horses can be born any color, lighten as they age, and eventually most will have either a completely white or "fleabitten" hair coat. Most "white" horses are actually grays with a fully white hair coat. A gray horse is distinguished from a white horse by dark skin, particularly noticeable around the eyes, muzzle, flanks, and other areas of thin or no hair. Variations of gray a horse may exhibit over its lifetime include:
**Salt and Pepper or "steel" gray: Usually a younger horse, an animal with white and dark hairs evenly intermixed over most of the body.
**Dapple gray: a dark-colored horse with lighter rings of graying hairs, called dapples, scattered throughout.
**Fleabitten gray: an otherwise fully white-haired horse that develops red hairs flecked throughout the coat.
**Rose gray: a gray horse with a reddish or pinkish tinge to its coat. This color occurs with a horse born bay or chestnut while the young horse is "graying out."

Less common coat colors

*Albino: There are no true albinos in the horse world (white coat with pink skin and pink eyes). If a foal is born a true albino, it either dies in the womb or shortly after birth. The equine coat color genetics factors that create true albinism, for reasons not yet fully understood, are lethal in horses. See "white" color, below for description of a truly white horse.
*Appaloosa or Leopard: There are a group of coat patterns caused by the leopard gene. It should be noted that not every horse with the leopard gene will exhibit hair coat spotting. However, even solid individuals will exhibit 'characteristics' such as vertically striped hooves, mottled skin around the eyes, lips, and genitalia, plus a white sclera of the eye. There are several distinct leopard patterns:
**blanket: white over the hip that may extend from the tail to the base of the neck. The spots inside the blanket (if present) are the same color as the horse's base coat.
**varnish roan: a mix of body and white hairs that extends over the entire body--no relation to true roan
**snowflake: white spots on a dark body. Typically the white spots increase in number and size as the horse ages.
**leopard: dark spots of varying sizes over a white body.
**few spot leopard: a nearly white horse from birth that retains colour just above the hooves, the knees, 'armpits', mane and tail, wind pipe, and face
**frost: similar to varnish but the white hairs are limited to the back, loins, and neck. ::Several breeds of horse can boast leopard-spotted (a term used collectively for all patterns) individuals including the Knabstrup, Noriker, and the Appaloosa.
*Black: Black is relatively uncommon, though not "rare." There are two types of black, fading black and non-fading black. Most black horses will fade to a brownish color if the horse is exposed to sunlight on a regular basis. Non-fading black is a blue-black shade that does not fade in the sun. Genetically, the two cannot yet be differentiated, and some claim the difference occurs due to management rather than genetics, though this claim is hotly disputed. Most black foals are usually born a mousy grey or dun color. As their foal coat begins to shed out, their black color will show through, though in some breeds black foals are born jet black. For a horse to be considered black, it must be completely black except for white markings. A sun-bleached black horse is still black, even though it may appear to be a dark bay or brown. A visible difference between a true black and a dark chestnut or bay is seen in the fine hairs around the eyes and muzzle; on a true black these hairs are black, even if the horse is sun-bleached, on other colors, they will be lighter.
*Brindle - One of the rarest colors in horses. Characteristics are any color with "zebra-like" stripes, but most common is a brown horse with faint yellowish markings.
*Buckskin- A bay horse with one copy of the cream gene, a dilution gene that 'dilutes' or fades the coat colour to a yellow, cream, or gold while keeping the black points (mane, tail, legs).
*Champagne: Produced by a different dilution gene than the cream gene. It lightens both skin and hair, but creates a metallic gold coat color with mottled skin and light colored eyes. Champagne horses are often confused with palomino, cremello, dun, or buckskins.
*Cream dilution, an incomplete dominant gene that produces a partially diluted coat color with one copy of the allele and a full dilution with two copies. Colors produced include Palomino, Buckskin, Perlino, Cremello and Smoky Cream or Smoky black.
*Cremello - A horse with a chestnut base coat and two cream genes that wash out almost all color until the horse is a pale cream or light tan color. Often called "white," they are not truly white horses, and they do not carry the white (W) gene. A cremello usually has blue eyes. "See also creme gene."
*Dun: Yellowish or tan coat with "primitive" markings, sometimes called "dun factors:" a darker-colored mane and tail, a dorsal stripe along the back and occasionally faint horizontal zebra stripings on the upper legs and a possible transverse stripe across the withers. There are several variations of dun:
**Grulla, Grullo or Blue Dun: A black horse with the dun gene. Coat is solid "mouse-colored" gray or silver with black or dark gray dun factors.
**Red dun: A chestnut base coat with dun factors. Coat is usually pale yellow or tan with a red mane, tail, and striping
**"bay dun" or "zebra dun" is terminology sometimes used to describe the classic dun color of yellow or tan with black mane and tail when necessary to distinguish it from red duns or grullos.
**"Buckskin dun" describes a dun that also carries the cream gene dilution and has a coat of pale gold with black mane, tail, legs and primitive markings.
*Palomino: chestnut horse that has one cream dilution gene that turns the horse to a golden, yellow, or tan shade with a flaxen or white mane and tail. Often cited as being a color "within three shades of a newly minted gold coin," palominos range in shades from extremely light, almost cremello, to deep chocolate, but always with a white or flaxen mane and tail.
*Perlino: similar to a cremello, but acts genetically a bay base coat with two dilute genes. Eyes are usually blue. Mane, tail and points are not black, but are usually darker than the body coat, generally a reddish or rust color, not to be confused with a red dun.
*Pinto: a multi-colored horse with large patches of brown, white, and/or black and white. Variations include:
**Piebald: a black and white spotting pattern (term more commonly used in the UK than the USA)
**Skewbald: a spotting pattern of white and any other color other than black, or a spotting pattern of white and two other colors, which may include black. (term more commonly used in the UK than the USA).
**Tobiano: Spotting pattern characterized by rounded markings with white legs and white across the back between the withers and the dock of the tail, usually arranged in a roughly vertical pattern and more white than dark, with the head usually dark and with markings like that of a normal horse. i.e. star, snip, strip, or blaze.
**Overo: Spotting pattern characterized by sharp, irregular markings with a horizontal orientation, usually more white than dark, though the face is usually white, often with blue eyes. The white rarely crosses the back, and the lower legs are normally dark. Variations include "Frame Overo" and "Spash White."
**Sabino: Often confused with roan or rabicano, a slight spotting pattern characterized by high white on legs, belly spots, white markings on the face extending past the eyes and/or patches of roaning patterns standing alone or on the edges of white markings
**Tovero: spotting pattern that is a mix of tobiano and overo coloration, such as blue eyes on a dark head. May also refer to horses with Tobiano coloring that carry a recessive overo gene.
**Paint: pinto horses with known Quarter Horse and/or Thoroughbred bloodlines. This is a separate breed of horse.
*Roan: a color pattern that causes white hairs to be evenly intermixed within the horse's body color. Roans are distinguishable from greys because roans typically do not change color in their lifetimes, unlike gray that gradually gets lighter as a horse ages. Roans also have heads that are either solid-colored or much darker than their body hair, and do not lighten. Variations of roan include:
**Red Roan: A chestnut base coat with roaning pattern with the mane and tail being the same red as the body. Red roans are also commonly referred to as a Strawberry Roan, and the term is occasionally is used to describe a Bay Roan. [ [http://www.aqha.com/association/registration/generalglossary.html AQHA General Glossary] ]
**Bay Roan: A Bay base coat with roaning pattern (the mane and tail of the Bay Roan will be Black). Bay roans are sometimes also called Red Roans. [ [http://www.aqha.com/association/registration/generalglossary.html AQHA General Glossary] ]
**Blue Roan: A black with roaning pattern, not to be confused with a gray or a blue dun/grullo. Grays not only lighten with age, but their heads tend to lighten before the rest of their bodies, while a roan tends to have a darker head. A blue dun will usually be a solid color and have dun striping, a blue roan has mixed-color hairs.
**Rabicano: A roan-like effect that is caused by a genetic modifier that creates a mealy, splotchy, or roaning pattern on only part of the body, usually limited to the underside, flanks, legs, and tail head areas. Unlike a true roan, much of the body will not have white hairs intermingled with solid ones, nor are the legs or head significantly darker than the rest of the horse.
*Silver dapple: Caused by a dilution gene that only acts upon black hair pigment, it lightens black body hair to a chocolate brown and the mane and tail to silver. The gene may be carried but will not be visible on horses with a red base coat.
*White : One of the rarest colors, a white horse has white hair and pink skin. These horses are born white, with blue or brown eyes, and remain white for life. A truly white horse occurs one of two ways: either by inheriting one copy of the dominant white (W) gene, or by being a "fully expressed" sabino (essentially a horse that is one big white spot). The vast majority of "white" horses are actually grays with a fully white hair coat. As noted above, there are no true albinos in the horse world.

Markings and other unique identifiers

White markings are present at birth and unique to each horse, making them useful in identifying individual animals. Markings usually have pink skin underneath them, though some faint markings may not, and white hairs may extend past the area of underlying pink skin. Though markings that overlie dark skin may appear to change, the underlying skin color and hair growing from pink skin will not. Horses may also be uniquely identified by an unusual eye color, whorls, brands and chestnuts.

Color breeds

Registries have opened that accept horses (and sometimes ponies and mules) of almost any breed or type, with color either the only requirement for registration or the primary criterion. These are called "color breeds." Unlike "true" horse breeds, there are few if any unique physical characteristics required, nor is the stud book limited to only certain breeds or offspring of previously registered horses. As a general rule, the color also does not always breed on (in some cases, due to genetic improbability), and offspring without the stated color are usually not eligible for recording with the color breed registry. The best-known color breed registries are for buckskins, palominos, and pintos. Some "true" breeds also have color that usually breeds on as well as distinctive physical characteristics and a limited stud book. These horses are true breeds that are said to have a "color preference." They are not color breeds, and include the Friesian horse (must be black for mainstream registration), the Appaloosa (Leopard or other small spotting patterns) and the American Paint Horse. In some breeds, though not all, offspring of animals registered in these stud books can also be registered, sometimes with restrictions, even if they do not have the desired color.

References

* [http://www.vgl.ucdavis.edu/services/coatcolorhorse.php "Horse coat color tests"] from the UC Davis Veterinary Genetics Lab
* [http://www.vgl.ucdavis.edu/services/coatcolor.php "Introduction to Coat Color Genetics"] "from" Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008
* [http://www.animalgenetics.us "Horse coat color and Genetic Disorder Testing"] Animal Genetics Inc. new Gray Gene Testing for horses

ee also

*Equine coat color genetics
*Horse markings