Color Genetics

"A Good Horse is Never a Bad Color"

Horse color genetics is a complicated subject. It is impossible to deny that the complexities can make it difficult to understand. By breaking down the subject into smaller pieces it is possible to begin to understand how the interactions of different factors result in the vast array of color in horses.

A first step is to separate ot white spots or hairs. Only concentrate on color. Following an appreciation of how the colors arise is possible to add the white, thereby understand the final combinations.

Color is the result of interaction of eleven or so different factors. Some of these are single genes, others are unknown genetically. Each unique combination results in a single color, so there are many, many possibilities. Some are common, some are rare, and some depend on the breed involved.

By: D. Phillip Sponenberg, DVM, PhD.

Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061

Genetic Control of Color

(Ignore the White!)

The three main colors of horses are bay, chestnut, and black.

All other colors can be built from these three, so understanding these three is the foundation for understanding all other colors.

Chestnut #1

Non-chestnut (black or bay) (EE.)

Chestnut horses are basically red, although many have “Bend Or” spots, which are dark or black spots up to a few inches across.

Bay #2

For the non-chestnut horses, bay (A+) is dominant to black (Aa).

This relationship is tricky. Chestnut, though recessive, masks whether a horse would have been black or bay. A mating of chestnut and black horses can result in bay foals, even though both chestnut and black are recessive to bay.

Shade #3

“Shade” is a complicated trait that is probably controlled by several genes rather than a few. “Shade” for convenience, can be considered to make the base color dark, medium or light. It interacts with the basic coat colors to produce more designations:

Color

Bay

Chestnut

Black

Dark Version

Blood bay, Mahogany bay

Liver Chestnut

Black

Medium Version

Red bay, Cherry bay

Red Chestnut

Black

Light Version

Sandy bay, God bay

Gold or Light Chestnut

“Summer” Black

Sooty #4

“Sooty” is a factor that adds black hairs into the base color. This changes the appearance from a clear color to a sooty color; and in some systems of color names will change names of some colors. The interaction of sooty and shade provide many, many different nuances of color.

Base Color:

Bay
Chestnut
Black

Sooty Variant:

Brown or Mahogany Bay (depending on naming system)
Liver Chestnut or Black Chestnut
Black

The mane and tail color on chestnut horses is variable. It ranges from a dark brown that is close to black, through bright reds, and on to the very pale flaxen colors that are nearly white. These changes are related to many, many different genes and are complicated.

Mealy #6

Mealy is a single, dominant gene (Pa+) which causes lighter areas on the belly, muzzle, inner legs, and over the eyes. It is usually ignored in color description, except for changing black to seal brown, and changing chestnut to sorrel for breeders of draft horses.

Cream #7

Dilutes red to yellow, and leaves black unaffected. With two doses it changes both red pigment and black pigment to cream, with pink skin and blue eyes.

One Dose

Buckskin

Sooty Buckskin

Palomino

Sooty Palomino

Smoky

Two Doses

Cream (technically perlino)

Cream (technically cremello)

Cream (technically smokey cream)

Dun #8

The linebacked dun gene (Dn+) is dominant. It lightens body color, leaving a stripe down the back, bars on the legs, and frequently a stripe on the withers.

Base Color

Bay

Brown

Buckskin

Chestnut

Sorrel

Palomino

Black

“Sooty” Black

“Light” Black

Cream

Dun Variant

Zebra Dun

Coyote Dun

Gold Dun

Red Dun

Apricot Dun

Linebacked Palomino

Grullo

Lobo Dun

Olive Dun or Olive Grullo

Linebacked Cream

The silver dapple gene (ZZ) is a dominant that acts to lighten black areas, and leaves red that are frequently confused with chestnut, but that lack the redness of chestnut. It lightens manes, tails, and lower legs to flaxen, or can leave them relatively unchanged.

Base Color

Black

Brown

Bay

Buckskin

Zebra Dun

Chestnut

Silver Dapple Variant

Chocolate Silver, Blue Silver, Silver Dapple

Brown Silver

Red Silver

Yellow Silver

Linebacked Yellow Silver

Chestnut (no visible evidence)

I haven’t found any examples of SSMA horses with the Silver Dapple gene. I’ll keep looking.

Champagne #10

The champagne gene (ChC) is a dominant that lightens black areas to flat light chocolate, skin to be pink or mottled, and eyes haz

Base Color:

Black
Palomino
Black

Champagne Variant:

Champagne
Amber champagne (gold or yellow with brown points)
God champagne (mimics palomino or light sorrel)
Vory champagne (very light, with dark blue eyes)

Brindle #11

The final color interaction is brindle.

This is rare indeed, and reorganizes the sooty countershading into vertical stripes.

Base Color:

Grullo Brindle

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