| Southwest Spanish Mustang Association |
| Preserving The Purest Spanish Mustangs In Existence Today |
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| Horse Color Genetics by D. Phillip Sponenberg, DVM, PhD. Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061 |
| Colorbook |
| 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 out white spots or hairs. Only concentrate on color. Following an appreciation of how the colors arise it 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. |
| 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 all of the others. |
| Chestnut #1 Chestnut (Ee) is recessive to nonchestnut (black or bay) (EE ). Chestnut horses are basically red, although many have "Bend Or" spots, which are dark or black spotsup to a few inches across. |
| Bay#2. For the nonchestnut 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. |
| Bay |
| Light Version |
| Chestnut |
| Blood bay, Mahogany bay |
| Red bay, Cherry bay |
| Red chestnut |
| Medium Version |
| Sandy bay, Gold bay |
| Dark Version |
| Black |
| Black |
| Liver Chestnut |
| Gold or Light Chestnut |
| Color |
| Black |
| “Summer” Black |
| 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: |
| Chestnut |
| Brown or Mahogany Bay (depending on naming system) |
| Bay |
| Base Color |
| Liver Chestnut or Black Chestnut |
| Sooty Variant |
| Black |
| 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. |
| #5 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. |
| Smoky |
| Sooty Palomino |
| Cream #7. The cremello gene (Crcr ) in one dose 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. |
| Bay |
| Two Doses |
| Cream (technically perlino) |
| Brown |
| Palomino |
| Cream (technically cremello) |
| Cream (technically cremello) |
| Cream (technically smoky cream) |
| Buckskin |
| Liver Chestnut |
| Cream (technically perlino) |
| One Dose |
| Base Color |
| Black |
| Sooty Buckskin |
| Chestnut/S orrel |
| Base Color |
| Apricot Dun |
| “Light” Black |
| Gold Dun |
| Sorrel |
| Coyote Dun |
| Linebacked Cream |
| Chestnut |
| Grullo |
| Dun Variant |
| Buckskin |
| Zebra Dun |
| Olive Dun or Olive Grullo |
| Black |
| Linebacked Palomino |
| “Sooty” Black |
| Brown |
| Bay |
| Red Dun |
| Cream |
| Lobo Dun |
| Palomino |
| 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. |
| Silver Dapple Variant |
| Linebacked Yellow Silver |
| Chestnut |
| Yellow Silver |
| Buckskin |
| Bay |
| Chestnut (no visible evidence) |
| Red Silver |
| Brown |
| Black |
| Chocolate Silver, Blue Silver, Silver Dapple |
| Brown Silver |
| Base Color |
| Zebra Dun |
| Silver Dapple#9 The silver dapple gene (ZZ ) is a dominant that acts to lighten black areas, and leaves red areas unchanged. It is rare, but increasing in frequency in some breeds. It results in colors that are frequently confused with chesnut, but that lack the redness of chestnut. It lightens manes, tails, and lower legs to flaxen, or can leave them relatively unchanged. |
| I haven't found any examples of SSMA horses with the Silver Dapple gene. I'll keep looking. |
| Palomino |
| champagne |
| base color |
| champagne variant |
| Black |
| Chestnut |
| gold champagne (mimics palomino or light sorrel) |
| Champagne #10 . The champagne gene (ChC ) is a dominant that is Lightens black areas to flat light chocolate, and red to light red or yellow. Skin to be pink or mottled, and eyes haz |
| vory champagne (very light, with dark blue eyes) |
| amber champagne (gold or yellow with brown points) |
| Bay |
| Grullo Brindle |
| Brindle #11 The final color interaction is brindle. This is rare indeed, and reorganizes the sooty countershading into vertical stripes. |
| Base Color |
| Brown |
| Lobo Dun |
| Brindle Variant |
