Silver dilution is a dominant trait. This means that a horse requires only one parent to carry and pass on the gene. Somewhat similar to the agouti gene, the silver dilution gene will only alter black pigmented horses (E/e or E/E). It has no effect on red pigmented horses (e/e). While the agouti gene alters the coat by controlling the distribution of the black pigment, the silver dilution gene does so by diluting areas of black pigment.
The effects of the silver dilution gene can vary greatly. When a uniform black horse is diluted by the silver gene, the mane and tail are lightened. The body is also lightened to a chocolate color, which is often dappled as well. A bay horse carrying the silver gene will usually have a lightened mane and tail, as well as lightened lower legs.
Genetic testing can be very important, as the silver gene is not always expressed. Although a red horse will not be diluted by the silver gene, it can be a carrier and pass the gene to its offspring. Because the gene is dominant, only one copy is needed for the horse to develop the silver colorations.
Silver dilution has been identified in a number of horse breeds, including the Quarter horse, the Rocky Mountain horse, the Icelandic horse, the Morgan, the Shetland pony, and the Miniature horse.
|Homozygous: Horse has two copies of the Silver Dilution gene mutation and will pass a copy to every offspring. Black-based horses will exhibit the dilution.
|Heterozygous: Horse has one copy of the Silver Dilution gene mutation and can pass a copy to any offspring. Black-based horses will exhibit the dilution.
|Negative: Horse is negative for the Silver Dilution gene mutation.