The Dilution Genes

Agouti, Cream, Dun, Roan, Silver Dapple, Champagne, Pearl

Many horse colors are the result of dilution genes acting on the base colors. They all work similarly in that they dilute the main body color, but not always the color of the legs, mane, and tail. Bay is the most basic dilution color, and it is caused by the agouti gene diluting black. The black body hairs are diluted to a shade of brown while the legs, mane, and tail remain black. Like most dilution genes, agouti is dominant, so if a horse carries it, it will be expressed.

Agouti is not actually a seperate gene, but rather a piece of the black gene called an allele. It can occur in three forms: A-agouti (meaning the horse is bay), a-non agouti (meaning the horse remains black), and At-brown (a color often confused with dark bay, but genetically different from bay).

This is Touch Gold, a light bay.

This is a red or blood bay.

This is Rambler's Renown, a Cleveland Bay. Note the lovely golden undertones and dappling. (Owned by IdleHour Stud)

This is Empire Maker, a dark bay.

The horse at left is also a bay, but the black on his legs is restricted to just his joints and pasterns. This is called a wild type bay. It is thought to be a primitive coloration as it is often found in old breeds like the Fjord and Przewalski's Horse.

 

Brown is also a dilution that acts on black as I mentioned above. Though it looks similar to dark bay, it is genetically different. Brown horses are characterized by having a black coat with brown hairs on their muzzles, flanks, inner forearms, and inner thighs. Seattle Slew is an excellent example of this color. (Photos by Anne Eberhardt)

 

Cream: Unlike agouti, which can only act on the black gene, cream can modify any color it acts in conjunction with, though it is most commonly seen combined with chestnut, bay, and black. The cream gene is an incomplete dominant, meaning it is always expressed when it's present, but it acts differently in its heterozygous (1 copy of the gene) and homozygous (2 copies of the gene) states. Simply put, horses with one copy of the cream gene will have a diluted coat; horses with 2 copies will have a doubly diluted coat. Double dilutes always have blue eyes. The cream gene does not effect black hairs in it's single form, only in it's double form.

 

Palomino: Chestnut + 1 Cream gene
Chestnuts have no black hairs, so the entire coat is diluted. The mane and tail are almost always white.

Cremello: Chestnut + 2 Cream genes
Cremello is basically a very pale palomino color---white markings are still discernable against the pale cream colored coat. Cremellos have blue eyes and light colored skin. (The only true pink skin is under white markings.)


Buckskin: Bay + 1 Cream gene
Because the cream gene doesn't affect black hairs, the dark points remain even after the bay body color has been diluted.

Perlino: Bay + 2 Cream genes
When two cream genes are present, the body color becomes very pale, and the black points are diluted to a red or brown color.

Smoky Black: Black + 1 Cream gene
The cream gene has very little affect on black hairs in its single state, so smoky black is very hard to distinguish from brown or (very sooty) dark bays. Often the best way to tell if the horse carries the cream gene is to have it genetically tested.

Smoky Cream: Black + 2 Cream genes
This Akhal Teke is thought to be a smoky cream. Notice how his points are still a darker shade than the rest of the body.



When sooty is present along with the cream gene, it can do strange things to the horse's coat. Chex Nu Jewel, a palomino Quarter Horse stallion, has most of his sooty coloration concentrated in his mane. (Photo by McBride Quarter Horses.)


Golden Belle is a sooty buckskin. (Bred, owned, and photographed by Red Fox Farm.)

 

Dun: Like the cream gene, the dun gene is also a dilution gene, but it is a complete dominant rather than an incomplete one, meaning heterozygous and homozygous duns look the same. It is often considered a "primitive" color because most very ancient breeds are predominantly or entirely dun, i.e. Przewalskis, Tarpans, etc. Duns are characterized by certain markings known as dun factors. They usually consist of a distinct dorsal (or eel) stripe down the back, leg barring (or zebra stripes), and cobwebbing on the face. As with the cream gene, the dun gene only dilutes the body color, not the points.

Red Dun: Chestnut + Dun
The chestnut color is diluted to a sandy color, but the mane, tail, and points remain chestnut. The dun factors tend to be the same reddish brown color as the points.

Bay Dun: Bay + Dun
The body color is diluted to a sandy color, but the points remain dark. This mustang shows another typical characteristic of duns---the light colored hairs on top of the mane and at the dock of the tail.

Black Dun: Black + Dun
This color is also called grulla, slate dun, or mouse dun. Once again, the points remain dark while the body color is lightened. (This is Quartz of Croila, a lovely Highland Pony stallion I met when we both still lived in Georgia.)

 

Silver Dapple: Silver dapple (also called taffy) is a dilution gene that only affects black (and thus bay), but not chestnut. It acts by changing black pigment to a chocolately color, and bay to a reddish, sometimes dappled color. (This dappling is unrelated to that caused by the grey gene.) While the legs are not affected by the silver dapple gene, the mane and tail change to a pale, flaxen color. Because of this, flaxen chestnuts are easily confused with silver dapple chestnuts. This color is found primarily in Rocky Mountain Horses, other related gaited horses, Mustangs, and Shetland Ponies.


This is silver dapple on black. Note the diluted mane and tail. Some silver dapple blacks fade with sun exposure to a dappled chocolate or even greyish-brown shade. The latter is very common in Shetland Ponies.


This is Amaretto Blu, a silver dapple bay Morab. The manes and tails of silver dapple horses often darken as they age, but they generally do retain flaxen tips. (Bred, owned, and photographed by Tamar's Ventures.)

This little cutie is a bay dun silver dapple: black + agouti + dun + silver dapple. (He's also a tobiano pinto.)

This is a silver dapple buckskin: black + agouti + cream + silver dapple.


Champagne: The champagne gene is a simple dominant dilution gene, much like dun. In other words, if a horse carries the champagne gene, he will be champagne in color. Champagne combined with chestnut is called "gold," with bay is "amber," and with black is "classic." Sometimes, champagne is combined with the cream gene as well, producing a color known as "ivory." It is known to act in conjunction with other dilution genes (i.e. dun), but those colors have yet to be named. Champagne horses are usually born with bright pink skin that becomes mottled as they age. They are also born with blue eyes that change to a hazel shade as they get older. The champagne gene is found most often in Tennessee Walking Horses, Missouri Foxtrotters, American Saddlebreds, and Quarter Horses. The best resource for more information and pictures of champagne horses is the Champagne Horse Association.

Gold Champagne: Chestnut + Champagne
The chestnut color is diluted to a golden color, similar to palomino. There is a distinguisihable difference because champagnes have hazel eyes and mottled skin. Many champagnes have a metallic or pearly sheen to their coats. (This is Glenknoll's Moregold, and ASB stallion.)

Amber Champagne: Bay + Champagne
The bay color is diluted to a golden color, similar to buckskin, but again is distinguishable because of the hazel eyes and mottled skin. (This is Doc’s Golden Champagne, an APHA gelding
co-owned by Natalia Tate and Jordan Pierce.)

Classic Champagne: Black + Champagne
The black color is diluted to a sort of mousie grey-brown shade with darker points. Just like the gold and amber champagnes, classic horses have the telltale hazel eyes and mottle skin. (This is Go Boy’s Champagne Pride, a TWH stallion owned by Laura Kidder.)
When combined with the creme gene, champagne horses are diluted to a nearly white shade called ivory champagne. Only classic champagnes combined with cream retain any noticeably dark pigment in their mane and tail and legs. There are some excellent pictures availble here.

 

Pearl: The pearl dilution is newly discovered. More info coming soon!

 

On to Other Modifiers

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