Equine Color Genetics - How Horses Get Their Color

The role of genetics in how horses get their colors is fascinating and complicated. While there are many facets of equine color genetics that researchers are still trying to understand, breeders have successfully used genetics to manipulate horse colors and breed horses in a wide range of colors and color combinations.

All the different horse colors we see result from two basic coat color genes - red base coat genes and black base coat genes, and the effects of dilution genes and modifier genes on these base coat colors.

• If a horse has a red base coat and there are no other genetic factors at play, the horse will have a brown body, a brown tail and a brown mane.
• If a horse has a black base coat and there are no other factors at play, the horse will have a black body, a black tail and a black mane.

It is important to note -

• Black base color genes are dominant genes - that means, that if both black and red color genes are present, the black gene will prevail and its effects will be visible.
• Red base color genes are recessive genes - that means that two red genes are needed, one from each parent, to get a red base color gene. If only one red gene is present, its effects will not be seen.

Many people assume bay to be a base color too, but it is not; it is actually a result of the Agouti modifier, about which we will read further on.

When dilution genes and modifier genes come into play, we get many color variations, depending on -

• Base coat color
• Dilution type
• Modifier type

Dilution genes, as the name indicate, dilute or lighten a coat color. A horse may have more than one dilution genes. Modifier genes, again as the name indicates, modify or alter a coat color. Modifiers may be -

• Base coat specific, affecting only a red base coat or a black base coat.
• Location specific, affecting only certain body areas.
• Non-specific, affecting both types of base coats and any area of the body.

There are four types of dilution genes -

Cream -

• Dominant gene.
• Affects only red base coat.
• Turns a brown horse to golden, with white mane and tail.
• Turns a black horse to smoky, otherwise no visible effect.
• Turns a bay horse to golden-brown, with no changes to the black mane and tail.

Champagne -

• Dominant gene.
• Affects both base coats.
• Results in eye colors like blue, green and amber.
• Results in pale, light, pink or brown skin. Skin may show brown or black freckles.
• On a red base coat, body lightens to golden brown, with flaxen mane and tail.
• On a black base coat, body lightens to a smoky shade or brown. Mane and tail may lighten or remain dark.
• On a bay horse, body lightens to golden brown. Mane, tail and points may lighten or remain dark.

Silver -

• Dominant gene.
• Does not affect red base coat.
• Affects black base coat only.
• Lightens black base coat to silver or brown, with white mane and tail. May result in a dappled coat.
• On a bay horse, brown body color remains unaffected, with lightening seen in points, mane and tail.

Dun -

• Affects both base coats.
• On a red base coat, leads to coat lightening and appearance of markings like shoulder stripes, dorsal stripes and leg bars. Points remain the same.
• On a black base coat, leads to body turning smoky or grey, with no changes to legs and head. Markings like shoulder stripes and leg bars can vary in color.
• On a bay horse, body may turn yellow or tan, with legs and head remaining dark. Marks like dark dorsal stripes, leg bars and web-like pattern on face may be seen.

The following are modifier genes -

Agouti modifier, also known as bay modifier -

• Affects only black base coat.
• Results in a brown body with black points, mane and tail.

Sooty modifier -

• Affects both base coats.
• Causes darkening and may affect any body part.
• May result in some dappling.

Brindle modifier -

• Rather rare and still being researched.
• Causes a pattern of dark markings over a lighter coat.

Gray modifier -

• Dominant gene.
• Affects both base coats.
• Causes coat colors to turn grayish over the years.

Flaxen modifier -

• Recessive gene, most probably.
• Affects only a red base coat.
• Causes a lightening of coat and turns mane and tail to golden, pale brown or white.

Mealy modifier, also known as pangare modifier -

• Affects both base coats.
• Causes a whitening or lightening of coat at the muzzle, eyes, elbows, belly and flanks.

Equine color genetics, By Dan Phillip Sponenberg, Wiley-Blackwell, 2003

http://scienceray.com/Biology/Zoology/Equine-Color-Genetics-Chestnut-Palomino-and-Cremello.293617

http://www.champagnewalkers.net/genetics.htm

http://www.champagnewalkers.net/TheDunFactor.htm

http://www.artbycrane.com/horsearticles/equinecolorgenetics.html

http://www.whitehorseproductions.com/ecg_basics4.html

http://www.aqha.com/magazines/aqhj/content/06february/oneinamillion.pdf

http://www.lattefarms.com/colorgenetics.html

http://www.vgl.ucdavis.edu/horse/hrseinfo.htm

http://www.horsecolor.info/articles.htm