Horse colors: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Nancy Sculerati MD
imported>Nancy Sculerati MD
No edit summary
Line 1: Line 1:
Horses have coats in shades of black, red, white, brown and grey, and mane and tail colors that either match, or contrast, with color of the coat. Those colors lend a distinctive appearance to the individual horse, and sometimes, typify an entire [[horse breed]]. The genetics behind the inheritance of these colors is a fascinating subject in and of itself, but  is also of practical interest to the horse breeder and owner. Knowledge of colors and markings are important in identifying horses, and in breeding selection for desireable traits. Not only are some colors and patterns in increased demand, but sometimes these features are written in to the breed standard of purbred horses. The [[Paint horse]], and the [[Appaloosa]], for example, were originally defined largely for the pattern of their coats. The [[Lipizzaner horse]]s, famous as the "dancing white stallions" are (like almost ''all'' "white" horses) almost always grey. Speculation about just how color and pattern is inherited in horses has probably been around as long as horse breeding has been, but it is only in the last decades that an understanding of the genetics has become sophisticated enough to go beyond speculation. Several [[DNA]] tests for color genes are now available, and a blood or hair root sample can reveal the [[genotype]] of a mare and stallion, allowing the breeder to predict the appearance of their offspring. Since some of those genes also influence eye and skin color, and the color of hoofs, as well as the patterns of color on the coat and the probability of white markings like socks, snipes, and blazes, accuracy of that prediction can go beyond simple base coat color.  
Horses have coats in shades of black, red, white, brown and grey, and mane and tail colors that can either match, or contrast, with color of the coat. Those colors lend a distinctive appearance to the individual horse, and sometimes, to entire [[horse breeds]]. The genetics behind the inheritance of these colors is a fascinating subject in and of itself, but  is also of practical interest to the horse breeder. Not only are particular colors and patterns in more demand by the horse buyer, but sometimes these features are written in to the breed standard. The [[Paint horse]], and the [[Appaloosa]], were originally defined largely for the pattern of their coats. The [[Lipizzaner horse]]s, famous as the "dancing white stallions" are (like almost all "white" horses) actually grey. Speculation about just how color and pattern is inherited in horses has been around as long as horse breeding has, but it is only in the last decades that an understanding of the genetics has become sophisticated enough to go beyond speculation. Several [[DNA]] tests for color genes are now available, and a blood or hair root sample can reveal the [[genotype]] of a mare or stallion. Since some of those genes also influence eye and skin color, and the color of hoofs, as well as the patterns of color on the coat and the probability of white markings like socks, snipes, and blazes, the predicted appearance of the foal from parents with known test results can be made with great accuracy. The genetics of color do not simply specify the pigment of horse hair, but also its distribution. In addition to genes that specify a hair pigment, like black, other genes can determine whether that color is limited to the very tip of a hair, or evenly distributed throughout the hair, and these genes are inherited as a separate factor than the color itself.  


=Solid colors=
=Solid colors=


==Red: chestnut and sorrel==
==Chestnut and sorrel==
 


Red haired horses are called by different names by English speaking people in different geographic areas. Equestrians from the [[United Kingdom]], and the [[British commonwealth]], as well as Americans from the East Coast call these horses ''chestnut'', and Americans from Western USA call them ''sorrel''. That distinction carries over to breeds and styles of riding, meaning that the [[quarter horse]]s so popular for [[western riding]] are likely to be called sorrel, and a [[warmblood]] competing in high level dressage is more likely to be called chestnut, even if both horses are the same shade of red, and in the same geographic area.
[[Image:Image:Mounted police officer in Helsinki Finland.jpg| left| caption: Chestnut police horse with blaze.]]
[[Image:Image:Mounted police officer in Helsinki Finland.jpg| left| caption: Chestnut police horse with blaze.]]




[[Image:Image:Chestnut head.jpg|right| This thoroughbred mare is chestnut. The most famous chestnut thoroughbred was probably the great racehorse, [[Secretariat]].]]
[[Image:Image:Chestnut head.jpg|right| This thoroughbred mare is chestnut. The most famous chestnut thoroughbred was probably the racehorse, [[Secretariat]].]]
 
==Black hairs: the E gene==
 


===Black or bay? : the agouti gene===
==Black or bay: the agouti gene==




Line 50: Line 47:




Most horses ''called'' "white" are actually grey. The gene responsible for this color is responsible for a process, "greying". Grey foals are born a different color than they will have as young horses, and that youthful adult color will often continue to change over time. In youth, many grey horses have lighter coats than manes and tails, and may have a black mane and tail through much of their adult life. Since the G gene is dominant, one parent of a grey horse will always be grey.
Most horses ''called'' "white" are actually grey. The gene responsible for this color is actually responsible for a process, "greying". Grey foals are born a different color than they will have as young horses, and that color will usually change over time, becoming lighter and lighter.  
 
===G gene===
 
Grey horses have a dominant form of the G gene, which excludes pigment from hair. The dominant G allele is not really a color, but a process of pigment loss. That process has been likened to human greying of hair, in which a black, red, or brown haired person becomes eventually silver-headed with age. "A young horse with a G allele will be born any color but gray and will gradually become white or white with red or black flecks as an aged animal. Earliest indications of change to gray can be seen by careful scrutiny of the head of a young foal, since often the first evidence of the gray hairs will be seen around the eyes. In intermediate stages of the graying process, the horse will have a mixture of white and dark hairs, a most confusing stage for trying to identify color."(reference for quote [http://www.vgl.ucdavis.edu/~lvmillon/coatcolor/coatclr3.html])


In youth, many grey horses have lighter coats than manes and tails, and may have a black mane and tail through much of their adult life.




[[Image:Image:Holsteiner 0001.jpg|right| Caption: This Holsteiner is a dappled grey with very light mane and tail.]]
[[Image:Image:Holsteiner 0001.jpg|right| Caption: This Holsteiner is a dappled grey with very light mane and tail.]]
==White or true albino horses: the W gene==
If a horse possesses the dominant allele W, it will, starting from birth, lack pigment in both skin and hair. The skin is pink and the hair white. The eyes brown are usually brown, but can be blue. This horse is called white, or sometimes, albino. The W allele is rare. All horses that are homozygous for the recessive pigment allele are ww, and those horses include every one of the other colors discussed in this article. In other words,  ''all'' non-white (meaning non-albino) horses are ww.




Line 106: Line 96:


=Blue-eyed horses=
=Blue-eyed horses=
=Genetic testing=
Various laboratories around the world offer genetic testing of horses on either a research or commercial basis. The University of California at Davis  Vetinary Genetics Laboratory is one such facility.




[[Category:CZ Live]]
[[Category:CZ Live]]

Revision as of 19:10, 31 December 2006

Horses have coats in shades of black, red, white, brown and grey, and mane and tail colors that can either match, or contrast, with color of the coat. Those colors lend a distinctive appearance to the individual horse, and sometimes, to entire horse breeds. The genetics behind the inheritance of these colors is a fascinating subject in and of itself, but is also of practical interest to the horse breeder. Not only are particular colors and patterns in more demand by the horse buyer, but sometimes these features are written in to the breed standard. The Paint horse, and the Appaloosa, were originally defined largely for the pattern of their coats. The Lipizzaner horses, famous as the "dancing white stallions" are (like almost all "white" horses) actually grey. Speculation about just how color and pattern is inherited in horses has been around as long as horse breeding has, but it is only in the last decades that an understanding of the genetics has become sophisticated enough to go beyond speculation. Several DNA tests for color genes are now available, and a blood or hair root sample can reveal the genotype of a mare or stallion. Since some of those genes also influence eye and skin color, and the color of hoofs, as well as the patterns of color on the coat and the probability of white markings like socks, snipes, and blazes, the predicted appearance of the foal from parents with known test results can be made with great accuracy. The genetics of color do not simply specify the pigment of horse hair, but also its distribution. In addition to genes that specify a hair pigment, like black, other genes can determine whether that color is limited to the very tip of a hair, or evenly distributed throughout the hair, and these genes are inherited as a separate factor than the color itself.

Solid colors

Chestnut and sorrel

caption: Chestnut police horse with blaze.


This thoroughbred mare is chestnut. The most famous chestnut thoroughbred was probably the racehorse, Secretariat.

Black or bay: the agouti gene

Bay

This quarter horse shows the brown colored body combined with black mane tail and lower legs that is called "bay". Bay is the most common coloration of all horses. The one white hind sock, and white star


Blood bay

When a bay horse has a particularly red coat, the name "blood bay" is often used.

caption: This Arabian is a blood bay.


Black

When a horse with black coat pigment is doubly recessive for the Agouti gene, pigment is spread evenly over each hair and the apearance is black rather than bay. Since a single copy of the dominant allele of an Agouti gene will make that horse bay, and there are two agouti genes in each horse, overall, black horses are unusual. When breeds of horses, like the draft horse XXX are characteristically black, both parents will carry a pair of recessive ag genes, and their foals will share their color. Fresians, a particularly elegant draft breed, are almost always black, for this reason.

caption: A black stallion
This black stallion has white socks and a white star with snipe.

True black or barn black?

Smoky black

Grey horses

This Andalusian is grey.


Most horses called "white" are actually grey. The gene responsible for this color is actually responsible for a process, "greying". Grey foals are born a different color than they will have as young horses, and that color will usually change over time, becoming lighter and lighter.

In youth, many grey horses have lighter coats than manes and tails, and may have a black mane and tail through much of their adult life.


Caption: This Holsteiner is a dappled grey with very light mane and tail.


Roan horses

Dilution genes: The creme gene

Unlike many other mammals, horses are that are albino are not simply unusual, but unhealthy. When a horse has light eyes and pink skin, along with a light coat the gene at work is a dilution gene, rather than some form of lethal white. [1]. The creme gene codes for a modification of color, in its dominant form, CR, there is no modification. A heterozygous recessive, CR/cr, will lighten coat color and a doubly recessive creme gene, cr/cr will doubly lighten it. The resulting color will depend on the base color of the horse and other factors, as outlined below.

Buckskin

Dilution of a bay horse results in buckskin coloration. This horse will have at least one copy of the dominant agouti gene, AG, so that black pigment on the coat is relegated to the mane, tail and points. A well-marked buckskin horse has a tan body, black mane and tail, and black "socks".

There are additional modifications to the body coat color that are known by the colloquial terms "smutty buckskin", "sooty buckskin" and "black buckskin", when a percentage of body hairs are entirely dark.


Grulla

Smoky black

Dilution of a black horse results in smoky black coloration. Such a horse, like all black horses, will be doubly recessive for the agouti allele (ag, ag) and black pigment will be evenly spread along each hair.

Palomino

A chestnut horse (also caled sorrel) with a single dilute gene yields a palomino horse. Like the buckskin, there can be additional modifications of coat color. A so-called "chocolate palomino" occurs when XXX. The Paso fino Tomaria's Gallardo is an example of a chocolate or smutty palomino.

Cremello

This horse has a cream-colored coat that can range from a rather deep cream to near white. It is a doubly dilute form of a chestnut horse, and will have pink skin and blue eyes.

Perlino

Another double dilute, the perlino XXX

Paint or pinto patterns

Medicine hat

Overo

Tobiano

Chestnut tobiano with blaze.


Blue-eyed horses

Retrieved from "https://citizendium.org/wiki/index.php?title=Horse_colors&oldid=140848"