Genetics of silver Experts say that the silver dilution gene was possibly present in Icelandic horse populations more than 1,000 years ago.
However, the exact cause of the silver coat color was discovered only recently.
In October 2006, an international team led by researchers at Uppsala University in Sweden, in association with BMC Genetics, published its study, “A missense mutation in PMEL 17 is associated with the silver coat color in the horse.” The study revealed that a mutation in the gene PMEL 17 on horse chromosome 6 causes one amino acid to be substituted for another and is responsible for a dilution of the black pigment in the hair.
The team In your mind, compare Andretti MVF AQHA with an ordinary bay and you’ll see where the silver dilution gene comes into play by diluting the black in the body, mane, tail and lower legs. Note how the silver gene has lightened the mane, tail and legs of this buckskin.
Stars Angel Too also carries the sooty gene which makes her coat darker than most buckskin silvers. confirmed that the silver allele (Z) is dominant and, if present, will almost always produce the silver phenotype. “Horses that are homozygous (ZZ) for silver seem to exhibit a more diluted coat color compared to the heterozygous (Zz) horses, but this indication needs to be verified,” wrote the researchers.
The exceptions are the red-based horses.
They do not show any effects of the silver mutation and are hidden carriers, capable of producing offspring with silver coat colors when crossed with horses carrying the black gene.
Once the silver dilution gene was mapped, a genetic test was developed and commercialized, giving breeders a definitive tool to distinguish silvers from other similar colors and identify red-based carriers.
When silvers are misclassified as reds, they usually go undetected until they produce a bay, brown or black foal with a red mate.
This raises a flag with breed registries since two red horses can only produce a red.
Before the silver test was available, the only other option was to test for the red factor to show the “chestnut” was genetically black. “Very, very few people can tell certain shades of chestnut from certain shades of silver bay visually,” said Trembreull. “I have years of experience telling the two apart, and there are individuals that I will not even attempt to classify as silver visually.
There are horses that the only way to determine if they are a silver bay or a chestnut is by red factor and silver testing.” Geneticists continue to study the silver dilution gene because of eye abnormalities found in Rocky Mountain Horses, Kentucky Saddle Horses and Mountain Pleasure Horses.
For years, these problems have been attributed to Anterior Segment Dysgenesis (ASD), a congenital, inherited but not progressive disease that can affect horses of any breed or color.
ASD was thought to be linked to the silver gene or color.
However, in a recent studies, the eye defects found in Rocky Mountain and Kentucky Saddle Horses were not those usually associated with ASD.
Also, researchers are not certain if the problems are linked to a specific bloodline or to the silver gene.
Other breeds have not found ASD in their silver horses.
Further research is necessary. Searching for silver Like any precious metal, silver is rare.
Where did the silver dilution gene come from? Are there many silver Paints? According to the Swedish-led study, silver coat colors are relatively common in Icelandic Horses, American Miniature Horses and Rocky Mountain Horses.
They have also been found in the Morgan Horse, American Saddlebred and Shetland Pony.
In the Morgan breed, “evidence suggests Headlight Morgan as the possible source of the gene,” said Lord.
Why is this 1893 “liver chestnut” stallion significant? “If he truly was carrying it, it may be much more widespread than we think, as he sired not only many Morgan foals, but was also used as a sire of Quarter Horses on the Burnett Ranch,” said Lord. 110 u PAINT HORSE JOURNAL u FEBRUARY 2009 TALIA CHIODO In 2002, the first silver Quarter Horse was officially discovered—Bar U Champ Binder, a 1981 silver stallion.
His sire, Bow Champ, was registered as sorrel, but is probably a silver bay, as he sired at least one bay foal from a chestnut mare. “It’s not 100 percent certain which side of the pedigree Bow Champ got it from,” said Lord. “Both parents are registered as sorrel.” A few months later, another silver Quarter Horse line was identified—Ms Barbarella, a 1993 mare registered as chestnut but with a silver phenotype.
Her pedigree included a long line of “roans” and “grays”—colors that could have been silver.
That line leads back to Smoky Wheat. “He is sired by Waggoner, a bona fide gray,” said Lord, “so Smoky Wheat and his offspring could have been gray plus silver.
But his dam is just identified as ‘Mare by Headlight Morgan,’ which takes us full circle to the horse identified as the likely source of the gene in Morgans.” Because APHA does not officially recognize the silver colors, it is impossible to accurately estimate the number of silver Paints.
According to silver enthusiasts, only the two registered Paints owned by Chiodo are known to carry the silver dilution gene, confirmed through genetic testing.
Stars Angel Too is a 1991 buckskin silver overo mare, registered as dun. “Angel is not a typical silver buckskin,” said Chiodo. “She also carries the sooty gene, which makes her coat much darker than a normal buckskin silver.
Many buckskin silvers look almost identical to traditional ‘buttermilk’ buckskins. “Angel is a unique color.
Her base color is a dark caramel.
Her legs are dark, but not black.
They are almost a deep burgundy.
Her mane and tail almost look dark red, but with flaxentinted ends.” Based on photos, Chiodo believes Angel got the silver gene from her dam, Silver Star Dust. “I theorize that Silver Star Dust received the gene from her sire, Silver Buzz,” explained Chiodo. “His grand-dam, Painted Doll, looks like she might be silver by her photo.
I haven’t been able to find any photos to trace the gene back any further than that.” Angel passed her silver gene to Wrangled From Heaven, a 2003 black silver tobiano mare, registered as dun. “Silver is notorious for ‘progressing’ over time,” explained Chiodo. “Bella is a completely different color than she was when she was a weanling or yearling. “Her mane and tail have always had dark roots with flaxen-tinted ends.
She has striped hooves and marbling on her legs.
In the summer, she usually develops a ton of gold dapples.” A silver lining Undoubtedly, more Paints carry the silver dilution gene.
Silver-colored horses are frequently misclassified and underestimated because it is so difficult to identify them visually. “It can be hard to trace the silver gene because silver ‘hides’ on red-based horses,” explained Chiodo. “The silver gene can be passed down through generations of red-based horses without anyone even realizing it, since it will only show itself when it is passed to a foal along with at least one copy of the black gene.” Most silvers are registered incorrectly as chestnuts, flaxen liver chestnuts or sooty palominos. “Remember, it’s only been a short time that the test has been available,” said Lord, “and probably very few owners or breeders know anything about the color.” As more breeders learn about the gene and its effects, they’ll turn to genetic testing for answers and perhaps find precious metal— silver Paints—hiding in plain sight in their pastures.
Read more about They have also been found in the Morgan Horse, American Saddlebred and Shetland Pony: