homozygotes, and silver black horses are heterozygous for this mutation could not be confirmed by DNA tests.
Some silver horses have congenital anomalies of the structure of eyes called anterior segment dysgenesis (ASD). Scientific literature also uses the name multiple congenital ocular abnormalities (MCOA). The phenotypes include:
Small pupils, which do not react to light or react poorly. (Application of dilating preparations does not have an effect.)
Abnormally formed pupils.
Hypoplasia (underdevelopment) of the iris, including its stroma.
Hypoplasia of iris formed by a pigmentary layer on the top edge of the pupil.
Abnormal structure of pectineal ligament.
Cataracts.
Cysts in the vitreous body.
Corneal thickening.
Abnormal arrangement of the eye lens.
Retinal dysplasia.
Abnormal circulation of intraocular liquid.
Defects of the ciliary body, such as small cysts in the junction between the sclera and cornea.
Cysts of the iris and ciliary body sometimes extending to the peripheral part of the retina.
Microphthalmia or megalophthalmia (abnormally small or abnormally large eye or eyes).
Abnormally large eyes.
The majority of the eye anomalies are connected with the forward segment of the eye, and some of them can occur independently, although there are also exceptions—such as the retinal displasia. Heterozygotes for the Silver gene are less affected than homozygotes. The vision of horses with cysts is usually normal. Unlike in normal horses with healthy eyes, the sclera of silver horses is sometimes pink, but not pigmented. Not all horses with MCOA have notable problems with their vision, but there are, of course, exceptions. For example, when cysts of a ciliary body are torn due to an impact, it can lead to the detachment of retina.
Most often MCOA is found in related breeds that originated from horses coming from Appalachia. These include Rocky Mountain Horses, Kentucky Mountain Saddle Horses, and Mountain Pleasure Horses. Similar abnormalities are also observed in other breeds, such as the Morgan, Belgian, Shetland Pony, American Miniature Horse, and Icelandic Horse. Affected horses can display abnormal behaviors due to the problems with their vision. Structural eye abnormalities are the result of a pleiotropic action of the PMEL17 gene. For this reason, since 1998, Kentucky Mountain Saddle Horses are required to pass veterinary inspection for the absence of vision problems before being allowed for breeding (animals with eye anomalies are excluded). The rules are not so strict for the Rocky Mountain Horse. Nevertheless, breeders of Rocky Mountain Horses, including those in Europe, do not recommend breeding carriers of the Silver gene.
COLORS DETERMINED BY THE CHAMPAGNE GENE
Unlike colors due to the Silver gene, champagne colors are absent in breeds in Russia and Europe. They are found in a limited number of breeds: the American Cream Draft, Tennessee Walking Horse, Missouri Fox Trotter, Quarter Horse, Paint Horse, Appaloosa, Rocky Mountain Horse, American Saddlebred, Kentucky Mountain Saddle Horse, Racking Horse, American Warmblood, Miniature Horse, North American Sportpony, and the Mustang.
Horses expressing the Champagne gene have the following features:
Specific age-dependent change of body color: The majority of foals of other colors is born light and darkens with age. In contrast, champagne foals are born with a dark hair and become lighter with age.
Color of eyes: Champagne horses are born with light blue eyes that gradually become greenish, then golden, and finally amber or hazel (Photos 63–65). However, the process of pigment accumulation in the iris can stop at any of these stages, and certain animals can have blue, green, or goldish eye color all their lives.
Speckled skin: Champagne foals are born with pink skin that darkens unevenly over time, developing specks. The skin of champagne horses differs from the skin of double cream diluted horses. It is dark pink, rather than light or bright pink in color. In adult champagne horses the dark, lilac specks are especially noticeable around the eyes, on the muzzle, under the tail, and on the genitals. Occasionally specks can be so dense they can merge together.
Goldish gloss of hair: Not all champagne horses have this trait, and at the same time not all horses with glossy hair are champagne. Nevertheless, this is considered a characteristic feature of champagne colors.
Dapples: Carriers of the Champagne gene sometimes have so-called “reverse” dapples—that is, not light against a dark background, as observed in the majority of dappled horses, but dark on a light background. However, not all champagne horses have such dapples, and reverse dapples are not unique to them. The International Champagne Horse Registry (ICHR—www.ichregistry.com) in the United States keeps records of horses having this color, regardless of their breed.
Classic Champagne
This is the least common champagne color—a derivative from black. Classic champagne, to a certain degree, is similar to grullo (Photo 66). This color varies from dark-ashy, chocolate, or brown to golden and bronze, dark and brass, or light gray-brown, with a darker (chocolate or dark-chestnut, but not black) mane and tail. The lower part of the legs can be darker than the horse’s body. The ashy hair sometimes has a bluish shade. The hooves of classic champagne horses are pigmented; the eyes are amber, or less often green.
Foals are born dark brown and lighten. Similar to black horses, champagne horses can become sun-faded in the summer. Experts separate this from a light classic champagne, which is an animal with very light bronze, almost yellow color, and those with a light but noticeable grayish shade.
Amber Champagne
This is a combination of the Champagne gene and a bay base (Photo 67). Amber champagne completely corresponds to its name: the body color is amber or goldish red. The mane, tail, ear rims, and lower part of the legs are chocolate or light brown. Occasionally there is an admixture of white, silvery, or pale-yellow hair in the mane and tail. This color can be confused with buckskin or silver buckskin.
The most typical amber champagne horse has body hair the color of saturated amber, apricot, or orange, and the mane, tail, and lower part of legs are chocolate. At birth, foals can be almost indistinguishable from classic champagne—it is with age that they become lighter. The eyes of an adult amber champagne horse are usually amber though they can remain light green in some animals. Hooves are pigmented.
Sable Champagne
Sable champagne is the Champagne gene on a seal brown base; therefore, it sometimes does not differ much from classic champagne color. The most common body color of a sable champagne horse is chocolate (of any intensity) with an ashy to dark or bronze shade (Photo 68). The guard hair is dark brown or chocolate; the lower part of the legs and ear rims often the same. For sable champagne horses that look similar to classic champagne, reliable distinction between them is possible via DNA analysis.
Gold Champagne
Gold champagne is a color determined by the Champagne gene combined with the chestnut base (Photos 69 & 70). Gold champagne horses have a goldish