Equus caballus, Horse: Coat Color

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Silver coat color in the horse

Brunberg E, Andersson L, Cothran G, Sandberg K, Mikko S, Lindgren G. A missense mutation in PMEL17 is associated with the Silver coat color in the horse. BMC Genet. 2006 Oct 9;7:46.

Phenotypic description of Silver colored horses.
A. A Black Silver Icelandic horse. A genetically black horse that exhibits the typical silver phenotype with a dark body with dapples and a shiny white mane and tail. Photo: Tim Kvick.
B. Two Black Silver Rocky Mountain Horses. Photo: Bob Langrish.
C. A Brown Silver Morgan horse. A genetically brown horse that shows the silver phenotype with the mane and tail diluted from black to white and the lower legs diluted from black to dark greyish. Photo: Laura Behning.
D. The legs of a Brown Silver horse. The lower legs are diluted from black to greyish. Photo: Laura Behning.

Phenotypic description of Silver colored foals.
A. A Silver colored Icelandic horse foal. Silver foals are generally very pale on the body with white mane and tail. Photo: Elsa Storgärds.
B. A striped hoof of a Silver colored Icelandic horse foal. Photo: Tim Kvick.
C. White eyelashes of a Silver colored Rocky Mountain Horse colt. Photo: Unknown.

A chestnut Morgan horse that carry the Silver mutation.
This particular individual (Amanda's Suzie Q) indicate that the Silver mutation in horses has little or no effect on pheomelanin (as mane does not seem to be diluted). Photo: Anthony Domire JR.

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Champagne dilution in horses

Cook D, Brooks S, Bellone R, Bailey E. Missense mutation in exon 2 of SLC36A1 responsible for champagne dilution in horses. PLoS Genet. 2008 Sep 19;4(9):e1000195.

Effect of Champagne gene action on base coat colors of horses (chestnut, bay, and black).
A) Chestnut – horse only produces red pigment.
B) Chestnut diluted by Champagne=Gold Champagne.
C) Bay – black pigment is limited to the points (e.g. mane, tail, and legs) allowing red pigment produced on the body to show.
D) Bay diluted by Champagne=Amber Champagne.
E) Black – red and black pigment produced, red masked by black.
F) Black diluted by Champagne=Classic Champagne.

Champagne Eye and Skin traits. A, B and C) Eye and skin color of foals. D and E) Eye color and skin mottling of adult horse.

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Dominant white (W) horses

Haase B, Brooks SA, Schlumbaum A, Azor PJ, Bailey E, Alaeddine F, Mevissen M, Burger D, Poncet PA, Rieder S, Leeb T. Allelic heterogeneity at the equine KIT locus in dominant white (W) horses. PLoS Genet. 2007 Nov;3(11):e195.

Dominant White Phenotype in Horses
(A) Franches-Montagnes mare with little residual pigmentation.
(B, C) Dominant white Franches-Montagnes stallion showing partial depigmentation as a colt and almost complete depigmentation at 4 years of age.
(D) Dominant white Thoroughbred stallion.
(E) Dominant white Arabian stallion.
(F) Camarillo White Horse.
(G) Immunohistochemistry using a polyclonal KIT antibody on a skin biopsy from a solid-colored horse. Blue staining indicates KIT expression throughout the epidermis. Melanin produced by melanocytes is visible as brown granules.
(H) Immunohistochemistry on a skin biopsy of a white horse. Note the weak blue staining and the complete absence of melanocytes and melanin. The bars correspond to 50 μm.

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Chestnut horses

Rendo F, Iriondo M, Manzano C, Estonba A. Identification of horse chestnut coat color genotype using SNaPshot. BMC Res Notes. 2009 Dec 16;2:255.

The Cantabrian Coast horse breeds of the Iberian Peninsula have mainly black or bay colored coats, but alleles responsible for a chestnut coat color run in these breeds and occasionally, chestnut horses are born. Chestnut coat color is caused by two recessive alleles, e and ea, of the melanocortin-1 receptor gene, whereas the presence of the dominant, wild-type E allele produces black or bay coat horses. Because black or bay colored coats are considered as the purebred phenotype for most of the breeds from this region, it is important to have a fast and reliable method to detect alleles causing chestnut coat color in horses.

The four native breeds analyzed. (a) Pottoka and (b) Jaca Navarra ponies; (c) Euskal Herriko Mendiko Zaldia and (d) Burguete heavy horse breeds.

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Silver (chocolate) coat color and MCOA in horses

Andersson LS, Juras R, Ramsey DT, Eason-Butler J, Ewart S, Cothran G, Lindgren G. Equine Multiple Congenital Ocular Anomalies maps to a 4.9 megabase interval on horse chromosome 6. BMC Genet. 2008 Dec 19;9:88.

A Silver colored Rocky Mountain Horse. The typical shiny white mane and tail as well as a slightly diluted body color with dapples is seen in this genetically black Silver colored horse. The phenotype is caused by dilution of eumelanin in the hair to white or grey. The dilution is most visible in the long hairs of the mane and tail. The horse has also been diagnosed with MCOA (Multiple Congenital Ocular Anomalies).

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