The Genetics of Champagne Coloring
- May 26, 2007
The champagne gene is a dominant dilution gene, first documented in 1996 by Philip Sponenberg, DVM, PhD, of Virginia Tech and Ann Bowling, PhD, of UC Davis. Prior to this the champagne gene was often misidentified. Many champagnes were mistakenly called "pumpkin-skinned palominos" due to their mottled skin and golden coloration. However, the champagne gene is distinctly separate from the cream gene (which causes palomino and buckskin) and the dun gene.
Many champagnes were mistakenly called "albinos" because of their bright blue eyes and pink skin at birth. However, true albinism is not common in horses, if it exists at all.
In addition to the bright blue eyes that later change to hazel or gold, and the pink skin that mottles with age, the champagne gene effects the coat color pigments. The gene causes red pigment to be diluted to gold, and black pigment to be diluted to chocolate.
Photos Courtesy Vonda Hamilton/CHBOA
The eye color of a champagne foal is bright blue (top photo at left). By the time the foal is three months old, the color might begin to change to green, and then gold. The eye color of an adult champagne can range from light gold, to green, to brown.
When champagne is combined with other genes, such as the cream gene or spotted pattern genes, the eyes of a champagne can remain bright blue through out its life.
However, having blue eyes at birth is not an indicator that a foal is champagne. Other dilutes (and some spotted breeds) are born with blue eyes and can strongly resemble a champagne, but are often found to carry a double cream or other modifier that is responsible for the blue eyes. It is the blue eyes in conjunction with other key characteristics that will ultimately identify a foal as having inherited the champagne gene.
The middle photo (at left) is an example of what the eye color on an adult horse that has inherited the champagne gene might look like.
The skin of a newborn champagne is bright pink. As the foal ages, dark mottling (freckles) will appear over the bright pink skin.
One place to check skin color and look for mottling is on the horse's head. Skin color and mottling can be observed around the eyes and on the muzzle. Notice the pink skin and heavy mottling on the muzzle of the filly in the lower figure (at left).
Another place skin coloration can be observed is around the horse's genitals. By lifting the horse's tail, the skin can be observed clearly in the areas that have no hair.
A chestnut, sorrel, or red-based horse that possesses the champagne gene will appear gold in color, often and easily misidentified as palomino. All of the red pigment in the horse's coat will be diluted to gold.
A black horse that possesses the champagne gene will appear chocolate, or even lilac. All of the black pigment will be diluted to chocolate. This color is often misidentified as dun or grullo. A bay horse, or one that displays agouti, that also inherits the champagne gene will appear buckskin in color, as the points will be diluted to dark chocolate and the red-based hair will be diluted to a mocha or buckskin color.
The champagne coat often has a distinct sheen to it. This is believed to be because of the unique structure of the hair shaft. The sheen is not itself an indicator of Champagne as a few other breeds also display this characteristic.
A gene is a code for a particular trait or feature. They control everything about an individual from appearance to metabolism and beyond.
Genes are found in sets of two, with the individual genes in the set being called an allele.
A horse that is heterozygous has two different alleles. It can be said that he or she carries one copy of a particular gene. The horse will produce a foal carrying the gene 50% of the time when bred to a horse without the gene. A horse that is homozygous has two like alleles. It can be said that he or she carries two copies of a particular gene. The horse will produce a foal carrying the gene 100% of the time whether or not the horse it is bred to carries the gene. In order for a horse to be homozygous for any gene, both of the horse's parents must have the gene and pass it. A dominant gene is a gene that "dominates." If a dominant gene is present, it will be expressed. It cannot be hidden.
Dominant genes are written as capital letters in genetic formulas. An example of a dominant gene is the black pigment gene, written as "E." A recessive gene is a gene that can "hide." In order for the gene to express itself, it must be in homozygous form (meaning both parents must pass the gene). Recessive genes are written as lowercase letters in genetic formulas. An example of a recessive gene is the red pigment gene, written as "e."
Step 1: Base color
All equine coat colors start out with a base color. Basically, underneath all of the other genes, all horses are either red or black. Some people may refer to bay as a base color, but bay is really black and agouti.
Step 2: Modifiers
Color modifiers change the appearance of the base color. Color modifiers include grey (progressive modifier that mixes white hairs with the coat color), roan (modifier that mixes white hairs with the body color--true roans have solid heads and legs), and the most prevalent of the modifiers: the agouti.
The agouti is a modifier that regulates the distribution of black pigment. Put simply, it limits the black on a black horse to the points (ears, legs, mane, and tail). A red-based horse can carry the agouti without showing it, as the agouti does not affect red pigment. However, a black horse cannot carry the agouti without expressing it.
If your horse is "a" (actually shorthand for "aa") then he/she is homozygous recessive for the agouti. Black horses are "aa." If a horse is "Aa", then he/she is heterozygous for the agouti and can throw horses with or without the agouti.
If a horse is "A" (shorthand for "AA"), then he/she is homozygous for the agouti and will never throw black-based horses without the agouti, meaning no blacks, smokey blacks, classic champagnes, blue roans, etc. Any black-based foal will have the black limited to the points. So, if you have a black mare and want a foal that is "any color except black," then breed your mare to a stud that is homozygous for the agouti.
Step 3: Dilution Genes
Dilution genes are genes that dilute, or modify, existing pigment (color) in the horse's coat. Some examples of dilution genes are: the champagne gene, cream gene, the silver gene, and dun gene. Each one is separate and affects the base color of the horse differently. A single horse can have several different dilution genes.
Step 4: Pattern Genes
Pattern genes effect the placement of white throughout the horse's coat. They are responsible for "spotted" horses.
The champagne gene can sometimes be mistaken for other dilution genes, and vice versa. See examples on the Champagne Horse Breeders and Owners Association Web site, www. www.CHBOA.com/comparisons.html, to the right to help you make an educated decision on the color of your horse. The pictures give a contrasting look at some of the more commonly mistaken colors of champagne. Flaxen gold champagne is often misidentified as palomino and registered as such. Just as often amber champagne is misidentified as buckskin.
Less often is the mistaken identity of a classic champagne with that of a grullo or dun, but one can see how this misidentification could and does happen.
If you have a horse that you think is champagne, look for the identifiers given in this article. Things to look for are bright blue eyes at birth that change to gold, green or amber within months; pink skin with mottling or freckling especially in the areas of the muzzle, eyes, and genitals; and often a characteristic sheen or glow to the coat.
Keep in mind that other breeds and dilution genes can also manifest with some of these characteristics, so if you are unsure whether or not your horse may be champagne, contact the Champagne Horse Breeders and Owners Association, www.CHBOA.com.
This information is provided courtesy of the Champagne Horse Breeders and Owners Association.
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