Equine coat color
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.
In the absence of DNA testing, chestnut and bay can be distinguished from each other by looking at the mane, tail and legs for the presence of black points.
[1][2] The word "points" is given to the mane, tail, lower legs, and ear rims with respect to horse coloration.
It acts on the extension gene, when present, to suppress black color to all but the extremities of the horse; the legs, mane, tail and tips of the ears.
Point coloration may also be visible on horses with other dilution genes that act upon a bay base coat.
These include: A dilution gene that produces what looks like point coloration, but from a completely different genetic mechanism is the dominant Dun gene, which dilutes the color of the body coat but not the points, including primitive markings—a dorsal stripe down the back and, less often, horizontal striping on the upper legs.
Similarly, darker coloration at the points is also preserved in horses with the roan gene, a patterning gene, producing a body coat of mingled white and dark hairs, but leaving the points the darker base color in all horses, not just those carrying agouti.
Most will eventually develop a complete white or a "fleabitten" coat, which retains speckles of the horse's original color.
The double cream dilute phenotypes overlap regardless of base coat color and often cannot be distinguished visually.
Sometimes the creme allele is combined with an unrelated dilution gene from another family, which creates a cremello-like coat.
[6] Several breeds of horse can boast leopard-spotted (a term used collectively for all patterns) individuals including the Knabstrupper, Noriker, and the Appaloosa.
There are several distinct leopard patterns: A pinto has large patches of white over any other underlying coat color.
Pinto spotting is produced by a large number of genetic mechanisms, with dozens now mapped and identifiable through DNA testing.
Rabicano: A roan-style effect that is caused by a yet-to-be-mapped genetic modifier that creates a mealy, splotchy, or roaning pattern on only part of the body, usually limited to the underside, flanks, legs, tail and 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.
Albinos, defined as animals with a white coat with pink skin and reddish eyes, are created by genetic mechanisms that do not exist in horses.
White markings are present at birth and unique to each horse, making them useful in identifying individual animals.
The champagne and pearl genes also produce lightened eye colors in the blue or green shades.
Most horses have a dark grayish hoof wall unless they have white leg markings, in which case they will have pale-colored hooves.
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.
