Colour Testing Information:

DNA testing is only available to ACE Group members.  You can request a DNA kit to be mailed to you by emailing [email protected]

Base Color:

Every horse has a base color, which can be black, bay, or red. This is controlled by the Extension (Red/Black Factor) and  genes. The Extension gene controls the production of black or red pigment throughout the coat. The allele for black color (E) is dominant over the red allele (e), so a horse only needs one copy of the black allele to appear black-based.

The Agouti gene can then modify black pigment by pushing it the the points of the horse, creating a bay. The Agouti gene is dominant, so a black pigmented horse only needs one copy of the Agouti gene (A) to appear bay. Agouti does not have any effect on red pigment.

There may be some variation in the intensity of the base colors, for example, dark bays compared to light bays or liver chestnuts to sorrels. This could be caused by a variation in the expression of the genes or interaction of other genetic factors.

Agouti (Bay/Black)

Description:

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). Agouti has been linked to a deletion of 11 nucleotides in the agouti gene. The 11 nucleotide deletion of this gene is the recessive form of the gene. 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. Therefore, a breeder might want to test a chestnut base horse to see if it is an Agouti carrier. Testing bay horses might be desired to see whether the horse carries one (Aa) or two (AA) copies of the Agouti allele. A homozygous Agouti (AA) horse will always pass Agouti to its offspring whereas a heterozygous (Aa) horse will have a 50% chance of passing on the gene. Another reason to test for Agouti might be if there is some doubt whether a black horse is truly black or a very dark bay. The effects of other genes might also make it hard to tell if Agouti is present or not.

This test does not determine if a horse is homozygous for black factor. To determine black homozygosity, a breeder should test for red/black Factor. See the Red/Black Factor below for more info.

Test Results:

Equine Genetics Research Centre – (Racing Australia) offers DNA testing for the Agouti gene that controls the distribution of black pigment. The genetic test verifies the presence of the dominant Agouti mutation and presents results as one of the following:

Equine Base Coat Red/Black Factor

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, sorrel to grey – 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.

Horses that are bay, black, grullo, buckskin, black/blue roan, etc. are black pigmented horses that carry at least one copy of the Black Factor (E) allele. The black (E) allele of the extension gene is dominant and causes a black pigmented base both in the heterozygous (Ee) and homozygous (EE) state. A horse that is heterozygous for Red/Black Factor means that it carries one copy of the black allele (E) and one copy of the red allele (e). A horse that is heterozygous for red/black factor can pass on either red or black pigment to its foals. A homozygous black (EE) horse means that it carries two copies of the black allele (EE). A homozygous black horse will always produce black based foals regardless of its mate.

Horses that are chestnut or sorrel, palomino, red dun, red roan, etc. are red pigmented horses and must carry two copies of the Red Factor (e) allele. The red (e) allele of the Extension gene is recessive and will only cause red pigmentation when the horse carries two copies of this allele; this is referred to as Homozygous red (ee). Therefore, a red based foal results when both parenst have passed on a copy of the red (e) allele.

Test Results:

Equine Genetics Research Centre – (Racing Australia) offers DNA testing for the extention gene effecting the Red / Black base coat color of a horse. The genetic test verifies the base coat color and presents results as one of the following: