The champagne gene is a simple dominant allele responsible for a number of rare horse coat colors. The most distinctive traits of horses with the champagne gene are the hazel eyes and pinkish, freckled skin, which are bright blue and bright pink at birth, respectively. The coat color is also affected: any hairs that would have been red are gold, and any hairs that would have been black are chocolate brown. If a horse inherits the champagne gene from either or both parents, a coat that would otherwise be chestnut is instead gold champagne, with bay corresponding to amber champagne, seal brown to sable champagne, and black to classic champagne. A horse must have at least one champagne parent to inherit the champagne gene, for which there is now a DNA test.
Unlike the genes underlying tobiano, dominant white, frame overo spotting and the Leopard complex common to the Appaloosa, the champagne gene does not affect the location of pigment-producing cells in the skin. Nor does the champagne gene remove all pigment from the skin and hair, as in albinism. Instead, the champagne gene produces traits known as hypomelanism, or dilution. Champagne is not associated with any health defects. Other dilution genes in horses include the Cream gene, Dun gene, Pearl gene and Silver dapple gene. Horses affected by these genes can sometimes be confused with champagnes, but champagnes are genetically distinct. Champagnes are not palominos, buckskins, or grullos, nor does the word champagne indicate that a horse is a shiny or light shade of another coat color.
This gene and the associated coat colors are only known in American breeds, especially the American Cream Draft, Tennessee Walker, American Saddlebred and Missouri Fox Trotter.
Coat colors
Champagne is a dominant trait, based on a mutation in the SLC36A1 gene. A horse with either one or two champagne genes will show the effects of the gene equally. However, if a horse is homozygous for a dominant gene, it will always pass the gene on to all of its offspring, while if the horse is heterozygous for the gene, the offspring will not always inherit the color. Horses with the champagne gene may also carry other coat color genes that affect their phenotype, or outward color.
Horses with the champagne gene have a lightened hair coat and specific eye and skin color traits. Black pigment in the coat, if present, is lightened to chocolate, while red pigment is lightened to gold. The precise champagne dilute coat color produced depends on the underlying base coat color. The effects of champagne plus additional coat color genes have their own distinct vocabulary and appearances;
It is difficult to distinguish between homozygous and heterozygous champagne, which is different from incomplete dominant dilutions such as the cream gene. However the 2008 study that mapped the gene and identified it as a dominant trait noted in passing that homozygotes may have less mottling or a slightly lighter hair color. The authors of this study noted that
The following are considered the most "basic" champagne coat colors:
Classic champagne is, as its name suggests, the coat color most associated with the champagne gene. It is produced by the action of champagne on a black coat. The body coat is chocolate, the mane and tail a darker shade. The legs may also be slightly darker. The overall effect has also been described as lilac, dark taupe, and even green. This color is most often misclassified as grullo, and in the past was sometimes called "lilac dun."
Sable champagne is produced by the action of champagne on a seal brown coat. It is visually difficult to distinguish from classic champagne, and can be confirmed by a DNA test negative for the recessive black (a) allele at Agouti.
Amber champagne is produced by the action of champagne on a bay coat. The coat is gold with chocolate points. Just as there are varying shades of bay, the gold body coat may vary in shade as well. The legs are often lighter than the mane and tail, and the colored points may be difficult to see. The mane and tail may also have "frosting" or light edges, a trait that also occurs in bay duns and some buckskins. Amber champagne can be confused with buckskin or bay dun.
Gold champagne is produced by the action of champagne on a chestnut coat. The coat is gold, and the mane and tail are typically ivory. In some cases, the mane and tail may be self-colored, matching the body coat. These gold champagnes are sometimes called "dark gold" and may be an all-over apricot shade. Dark gold champagnes can be confused with red dun, while those with paler manes and tails were historically called "pumpkin-skinned palominos."
Apart from the unique shades, there are several qualities of the champagne coat that may be used to help identify them. Champagne coats often have an unusual sheen. This sheen makes champagnes difficult to photograph accurately, as the appearance of the coat depends on the lighting. Not all champagne horses have this sheen, and there are many extremely shiny non-champagne horses, so a "sheen" in and of itself does not indicate the champagne gene. The coat may also exhibit reverse dappling, though this is also an unreliable indicator.
Skin and eyes
The color of the skin is the single most important visual identifier of champagne horses: in the adult horse, the skin is "pink with abundant dark freckles, except under white markings." The freckles - not mottles, splotches, specks, or blotches - are dark and may have a purple cast, and are small and numerous. By comparison, mottling associated with the Leopard complex is large and blocky alternations between true black or charcoal-colored skin and pigmentless-pink skin. The skin of cremellos and perlinos is pigmented-pink, and exhibit a scant few tiny black specks. Homozygous pearls and pearl-cream combinations also exhibit some freckling of the skin, however this is muted in comparison to the freckles of champagne skin. The skin may exhibit an overall lavender tone. The color qualities of the skin are most evident around the eyes and muzzle, under the tail, and on the udder or sheath.
The eyes of an adult champagne horse are most often described as hazel or amber.Cook et al. 2008. "To be characterized as possessing the champagne phenotype, horses exhibited a diminished intensity of color (dilution) in black or brown hair pigment and met at least two of the three following criteria: 1) mottled skin around eyes, muzzle and/or genitalia, 2) amber, green, or light brown eyes, or 3) blue eyes and pink skin at birth" In the newborn or very young foal, the eyes are bright blue to blue-green and the skin is bright pink.Cook et al. 2008. "champagne foals are born with blue eyes, which change color to amber, green, or light brown and pink "pumpkin skin" which acquires a darker mottled complexion around the eyes, muzzle, and genitalia as the animal matures. Foals with one copy of CR also have pink skin at birth but their skin is slightly darker and becomes black/near black with age." The champagne blue foal eye is creamier than other types of blue eye such as the bright, unpigmented blue seen on some pinto horses.
In the past, some breeders and horse owners had concerns that horses with light-colored skin and eyes were not healthy. However, the lightening of these parts of the horse due to the champagne gene is not known to be linked to any health or genetic defects. While horses with white markings may sunburn on exposed unpigmented skin, the freckled-pink skin of a champagne horse is said to tan instead.Identifying the Champagne Colored Horse. "The pink skin of a Champagne horse is "pigmented pink" -- not the pigment-free, paler pink color found under all white markings of all horses. It will often tan." In addition, the color of the hoof has no bearing on its strength.
Interaction with other coat color factors The presence of other coat color modifying alleles has no effect on whether or not a horse has the champagne trait. However, different traits may interact; they may suppress, enhance, obscure or cancel out various tell-tale clues to the genetic identity of a coat color. Coat colors involving multiple genes often have an unexpected appearance and unique terminology. This type of genetic interaction is called epistasis.
Horses with both the champagne gene and the cream gene are the most common combination. The cream gene is responsible for the palomino, buckskin and cremello coat colors, and is a dose-dependent or incomplete dominant, meaning that a horse with only one copy is visibly different from a horse with two copies of the gene. A single copy of the cream gene dilutes red pigment in the coat to gold or yellow, and has a slight effect on the skin and eye color. The black pigment is lightened little, if at all. Two copies of the cream gene dilute both red and black pigments in the hair to cream or ivory, dilute the skin to a rosy-pink and the eyes to pale blue. The cream gene and champagne gene have an additive or enhancing interaction. Horses with the champagne gene and a single cream gene typically have lighter yellowish or blue eyes and paler, more faintly freckled skin. Gold cream or Ivory champagne refers to an otherwise-chestnut coat affected by the champagne gene and a single copy of the cream gene. The mane, tail, and coat of gold creams are typically ivory and difficult to distinguish from cremello, other than by the skin and eyes. Amber cream, similarly, is an otherwise-bay coat affected by the champagne gene and a single copy of the cream gene. The mane and tail of a typical amber cream are a warm yellowish-brown and are often frosted. The legs may also be a light chocolate brown, but need not be. The body coat is a shade of ivory, usually darker than a gold cream. Their points are substantially darker than those of a perlino, and they have champagne skin and eye traits. Sable cream is a seal brown coat affected by champagne and a single copy of the cream gene. Sable creams may more closely resemble amber cream or classic cream. Most are several shades darker, with a cooler hue, than amber creams. Classic cream is a black coat affected by champagne and a single copy of the cream gene. Classic cream coats should resemble classic champagne shades, being only slightly lightened by the cream gene. Their coats may have a cooler hue. Double cream champagne is a coat of any color affected by champagne and both copies of the cream gene. Unlike the coat colors associated with only a single cream gene, double cream champagnes (respectively prefixed with "gold," "amber," etc.) retain no obvious champagne traits. Their skin is clear pink without freckling, and the eyes are pale blue. The terms "cremello champagne", "perlino champagne" and so forth are also acceptable.
Horses with both the champagne gene and the dun gene are also well-recorded. The dun gene is responsible for flat, diluted coat colors and vivid primitive markings. Bay dun is thought to be the wildtype horse coat color. Dun does not affect skin or eye color, but dilutes red pigment to yellow and black pigment to slate gray. Champagne horses with the dun gene will have slightly further-diluted coats compared to non-dun champagnes, and will always exhibit striking primitive markings, such as a dorsal stripe and zebra-like stripes on the legs. Naming schemes are much the same as with champagne-cream combinations. Champagne-dun combinations retain their champagne eye and skin traits. The coats are distinguishable from non-champagne duns in that they are several shades lighter, black pigment is chocolate rather than slate, and they may exhibit a sheen. The coats are distinguishable from non-dun champagnes in the presence of primitive markings and a flatter tone.