Information about Coat Colours in horses

Within the large number of coat colour factors three genetic features explain the major differences in coat colours. These are the Agouti Factor, the Red Factor (Extension locus) and the Cream Dilution Factor. In the table below, possible combinations are indicated:

Genetic Factor Coat Colour Agouti Red Factor, Extension Cream Dilution locus Factor Black a/a E/E or E/e N/N Brown or Bay A/A or A/a E/E or E/e N/N Chestnut A/A, A/a or a/a e/e N/N Smoky black a/a E/E or E/e N/Cr Buckskin A/A or A/a E/E or E/e N/Cr Palomino A/A, A/a or a/a e/e N/Cr Smoky cream a/a E/E or E/e Cr/Cr Perlino A/A or A/a E/E or E/e Cr/Cr Cremello A/A, A/a or a/a e/e Cr/Cr

The Agouti Factor encloses the following results:

A/A In the hair, the black pigment is point shaped distributed. Basic colour is bay or brown in the absence of other modifying genes. A/a In the hair, the black pigment is point shaped distributed. Basic colour is bay or brown in the absence of other modifying genes. a/a Only recessive allele detected. Black pigment distributed uniformly. Basic colour is black in the absence of other modifying genes.

The Red Factor (Chestnut) encloses the following results: e/e Only red factor detected. Basic colour is sorrel or chestnut in the absence of other modi- fying genes. E/e One copy of red factor detected. Basic colour is black, bay or brown in the absence of other modifying genes. E/E No red factor detected. Basic colour is black, bay or brown in the absence of other mod- ifying genes.

The Cream Dilution Factor encloses the following results:

N/N Cream Dilution Factor not found. Basic colour is sorrel or chestnut, bay or black in the absence of other modifying genes. N/Cr Heterozygous, dilute, one copy of “Cream gene”. Typical colours are palomino, buckskin and smoky black in the absence of other modifying genes. Cr/Cr Double dilute (two copies of “Cream gene”). Typical colours are cremello, perlino and smoky cream in the absence of other modifying genes.

In addition to these three Coat Colour Factors, subsequently information about several other genetic factors that are known (other dilution factors and white patterns). The information about these tests is also available at www.certagen.de. Page 1 of 3 DNA is our core

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The Champagne Dilution Factor is a dominant gene that dilutes hair pigment from black to brown and red to gold. Champagne on a chestnut background produces a gold body colour and often a flaxen mane and tail that can be mistaken for palomino. Champagne on a bay background (“Amber”) produces a tan body colour with brown points. Champagne on a black background (“Classic”) produces a darker tan body with brown points. The skin of Champagne-diluted horses is pinkish/lavender toned and becomes speckled with age; the speckling is particularly noticeable around the eye, muzzle, under the tail, udder and sheath. The eye colour is blue-green at birth and darkens to amber as the horse ages.

The Champagne Dilution Factor encloses the following results:

N/N Champagne Dilution Factor not detected. Basic colour is sorrel or chestnut, bay or black in the absence of other modifying genes. N/Ch Heterozygous, dilute, one copy of “Champagne gene”. Chestnut colour is diluted to gold, bay to tan with brown points and black to darker tan with brown points in the absence of other modifying genes. Ch/Ch Homozygous, dilute, two copies of “Champagne gene”. Chestnut colour is diluted to gold, bay to tan with brown points and black to darker tan with brown points in the absence of other modifying genes.

The Silver Dilution Factor (Z-locus) dilutes the black pigment but has no effect on red pigment. The Silver Dilution Factor encloses the following results:

N/N Silver Dilution Factor not detected. Basic colour is sorrel or chestnut, bay or black in the absence of other modifying genes. N/Z Heterozygous, one copy of “Silver gene”. Black is diluted to chocolate with flaxen or light- ened mane and tail; Bay is diluted to lightened black pigment on lower legs, mane and tail; Chestnut is not diluted. Z/Z Homozygous, two copies of “Silver gene”. Black is diluted to chocolate with flaxen or lightened mane and tail; Bay is diluted to lightened black pigment on lower legs, mane and tail; Chestnut is not diluted.

The Pearl Dilution Factor (Prl-Locus), also called “Barlink Factor”, encloses the following results:

N/N Pearl Dilution Factor not detected. Basic colour is sorrel or chestnut, bay or black in the absence of other modifying genes. N/Prl Heterozygous, one copy of “Pearl gene”. Only dilution if Cream dilution is also present. If Cream dilution is also present, a pseudo-double Cream dilute phenotype is the result. Prl/Prl Homozygous, two copies of “Pearl gene”. A chestnut base colour is diluted to a uniform apricot colour of boy hair, mane and tail.

The Grey Factor encloses the following results:

N/N The horse is no carrier of the mutation responsible for the coat colour Grey. N/G or G/G The horse is hetero- or homozygous for the mutation responsible for the coat colour Grey. The horse will turn grey.

The coat colour Grey is being caused by a duplication of a part of the DNA. The test does not discriminate between horses carrying 1 or 2 copies of the duplication. All horses carrying the duplication will turn grey.

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The Tobiano Factor produces a white spotting pattern that is clearly marked and characterized by white areas across the spine that extends downward between the ears and tail.

The Tobiano Factor encloses the following results:

N/N No Tobiano factor N/TO Carrier of Tobiano factor. The horse is Tobiano and (statistically) half of the offspring will inherit Tobiano. TO/TO Homozygous Tobiano. The horse is Tobiano and all offspring will inherit Tobiano.

The Overo Factor produces a white spotting pattern with white patches on the side with a “frame” of colour surrounding the white. The Overo allele is dominant, all Overo horses are heterozygous for the Overo factor since it is lethal when homozygous.

The Overo Factor encloses the following results:

N/N No Overo factor N/O Carrier of Overo factor (Carrier OLWS!). The horse is Overo. O/O Overo Lethal White Syndrome (OLWS), lethal

The Sabino Factor produces a white spotting pattern that is described as irregular spotting usually on the legs, belly and face, often with extensive roaning. A mutation has been discovered that produces one type of sabino pattern, it has been named Sabino1 as it is not present in all sabino-patterned horses.

The Sabino1 Factor encloses the following results:

N/N The horse is no carrier of the Sabino1 mutation. N/SB1 One copy of the Sabino1 mutation detected. Horses typically may have 2 or more white legs, blaze, spots or roaning in the midsection and jagged margins around white areas. SB1/SB1 Two copies of the Sabino1 mutation detected. Complete or nearly complete white phe- notype expected.

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