The Extension (Red Factor) and Agouti genes define the Base Coat Color (Bay, Black or Chestnut) of an Arabian horse. A breeder can
determine the color odds for a foal, providing these genes are known for the sire and dam.
Definitions |
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E = Black Pigment |
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e = Red Pigment |
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A = Agouti |
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a = No Agouti |
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Rules |
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Black (E) is dominant over Red (e). |
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Agouti (A) is dominant over Non-Agouti (a). |
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The Agouti gene restricts Black pigment to the points (mane, tail, lower legs & ears). |
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Color |
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Bay horses have at least 1 Black gene and at least 1 Agouti gene: EEAA, EeAA, EEAa or EeAa. |
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Black horses have at least 1 Black gene and no Agouti gene: EEaa or Eeaa. |
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Chestnut horses have 2 Red genes: eeAA, eeAa or eeaa. |
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Bay EEAA |
Bay EeAA |
Bay EEAa |
Bay EeAa |
Black EEaa |
Black Eeaa |
Chestnut eeAA |
Chestnut eeAa |
Chestnut eeaa |
Bay EEAA |
100% Bay |
100% Bay |
100% Bay |
100% Bay |
100% Bay |
100% Bay |
100% Bay |
100% Bay |
100% Bay |
Bay EeAA |
100% Bay |
75% Bay 25% Chestnut |
100% Bay |
75% Bay 25% Chestnut |
100% Bay |
75% Bay 25% Chestnut |
50% Bay 50% Chestnut |
50% Bay 50% Chestnut |
50% Bay 50% Chestnut |
Bay EEAa |
100% Bay |
100% Bay |
75% Bay 25% Black |
75% Bay 25% Black |
50% Bay 50% Black |
50% Bay 50% Black |
100% Bay |
75% Bay 25% Black |
50% Bay 50% Black |
Bay EeAa |
100% Bay |
75% Bay 25% Chestnut |
75% Bay 25% Black |
56.25% Bay 18.75% Black 25% Chestnut |
50% Bay 50% Black |
37.5% Bay 37.5% Black 25% Chestnut |
50% Bay 50% Chestnut |
37.5% Bay 12.5% Black 50% Chestnut |
25% Bay 25% Black 50% Chestnut |
Black EEaa |
100% Bay |
100% Bay |
50% Bay 50% Black |
50% Bay 50% Black |
100% Black |
100% Black |
100% Bay |
50% Bay 50% Black |
100% Black |
Black Eeaa |
100% Bay |
75% Bay 25% Chestnut |
50% Bay 50% Black |
37.5% Bay 37.5% Black 25% Chestnut |
100% Black |
75% Black 25% Chestnut |
50% Bay 50% Chestnut |
25% Bay 25% Black 50% Chestnut |
50% Black 50% Chestnut |
Chestnut eeAA |
100% Bay |
50% Bay 50% Chestnut |
100% Bay |
50% Bay 50% Chestnut |
100% Bay |
50% Bay 50% Chestnut |
100% Chestnut |
100% Chestnut |
100% Chestnut |
Chestnut eeAa |
100% Bay |
50% Bay 50% Chestnut |
75% Bay 25% Black |
37.5% Bay 12.5% Black 50% Chestnut |
50% Bay 50% Black |
25% Bay 25% Black 50% Chestnut |
100% Chestnut |
100% Chestnut |
100% Chestnut |
Chestnut eeaa |
100% Bay |
50% Bay 50% Chestnut |
50% Bay 50% Black |
25% Bay 25% Black 50% Chestnut |
100% Black |
50% Black 50% Chestnut |
100% Chestnut |
100% Chestnut |
100% Chestnut |
Besides Bay, Black and Chestnut, the Arabian Horse Association lists Gray and Roan as color options.
While both effect the appearance of a horse, neither identify their base coat color.
Gray is a dominant modifier gene which causes the coat to progressively lose pigment. At birth, the base coat color of Bay, Black or Chestnut is apparent and the Red Factor and Agouti rules still apply.
Roan is not a Color, but rather a Pattern of white hair mixed within a base coat color of Bay, Black or Chestnut. It is possible to have a Bay Roan, Black Roan or Chestnut Roan.
ETALON Diagnostics provides DNA testing services for Red Factor, Agouti, Gray and much more.
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