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Description

Equine coat color is built on one of two possible base pigments: red or black. The extension gene controls the production of this base pigment [red or black]. All of the coat colors we see today, from white to black and sorrel- every single one of them begins with either a red or black base pigment. All horses will have the genetics for black or red pigment, regardless of their physical appearance. There are a number of dilutions patterns and modifiers which a horse can carry that affect the base pigment of a horse.

Bay - E_ A_ (Bay) OR E_ At_ (Seal Bay) OR E_ A+_ (Wild Bay) - The Agouti gene controls the distribution of black pigment. This pigment can be either uniformly distributed or distributed to "points" of the body [ear rims, lower legs, mane, tail]. Only when the agouti gene is homozygous for the deletion [aa] is the black pigment evenly distributed. Heterozygous [Aa] or homozygous for the absence of the 11 nucleotide deletion [AA] results in point distribution of black pigment. Agouti has no effect on homozygous positive red factor [ee] horses as there has to be black pigment present for agouti to have an effect. Agouti is not shown physically on red [ee] horses.

From Left to Right, Row 1; Light Bay, Standard Bay, Blood Bay, Dark Bay
From Left to Right, Row 2; Seal Bay, Wild Bay

Description

Equine coat color is built on one of two possible base pigments: red or black. The extension gene controls the production of this base pigment [red or black]. All of the coat colors we see today, from white to black and sorrel- every single one of them begins with either a red or black base pigment. All horses will have the genetics for black or red pigment, regardless of their physical appearance. There are a number of dilutions patterns and modifiers which a horse can carry that affect the base pigment of a horse.

Bay - E_ A_ (Bay) OR E_ At_ (Seal Bay) OR E_ A+_ (Wild Bay) - The Agouti gene controls the distribution of black pigment. This pigment can be either uniformly distributed or distributed to "points" of the body [ear rims, lower legs, mane, tail]. Only when the agouti gene is homozygous for the deletion [aa] is the black pigment evenly distributed. Heterozygous [Aa] or homozygous for the absence of the 11 nucleotide deletion [AA] results in point distribution of black pigment. Agouti has no effect on homozygous positive red factor [ee] horses as there has to be black pigment present for agouti to have an effect. Agouti is not shown physically on red [ee] horses.

From Left to Right, Row 1; Light Bay, Standard Bay, Blood Bay, Dark Bay
From Left to Right, Row 2; Seal Bay, Wild Bay