GETTING TESTED
All four tests covered in this article are available through the APHA’s official labora- tory at UC–Davis for $25 each. You can also opt for the Comprehensive Coat Color Test—a thorough screening that tests for the presence of red factor, agouti, cream, pearl, champagne, dun, silver, gray, tobiano, OLWS, Sabino 1 and three splash whites—for $110. Since parent- age verification is required for all racehorses, you can test for coat colors and fulfill the DNA genetic typing requirement with just one hair sample. The DNA Hair Kit Order Form and fees are available online or by calling APHA Mem- berCare at (817) 222-6423.
The iconic image of a splash overo is of a horse that looks like he’s been dipped in white paint—APHA Supreme Champion Gambling Man is one of the most-recognized splash white Paints.
Splash White 1, 2 and 3 Splash white is a complex and vari- able spotting pattern producing an extremely wide blaze, extensive leg markings, variable belly spots and often blue eyes—think of APHA Supreme Champion Gambling Man and legendary Paint reiner Colonels Smokingun. Some, but not all, splash white horses are deaf.
A study announcing the discovery
of three splash white mutations was published in 2012, offering breeders new genetic tests to identify carriers of SW1, SW2 and SW3. These are believed to be incomplete dominant
genes, meaning a foal only has to inherit one copy to display splash characteristics. According to the University of California–Davis Veterinary Genetics Laboratory website, “SW1 has been found in several breeds—Quarter Horse, Paint, Trakehner, Miniature Horse, Shetland Pony and Icelandic Horse—and may be present in other breeds as well. Horses homozygous for SW1 have been identified, which suggests that this mutation is not homozygous lethal. SW2 and the rare SW3 occur exclusively in certain lines of Quarter Horses and Paints. Based on predictions from other species, SW2 and SW3 may be homozygous lethals and thus matings of two horses that carry SW2 or SW3 should be avoided.” Not all horses classified as splash white carry SW1, SW2 or SW3. Researchers believe there are other, undiscovered mutations also
WHAT ABOUT GENETIC DISEASES?
According to a study published in 2006, racing-bred Quarter Horses and Paints were at the least risk of carrying genetic diseases. Nonetheless, it’s still wise to test breeding stock for inheritable conditions, especially stallions. UC–Davis offers a Comprehensive Disease Diagnostic test that screens for the presence of HERDA, HYPP, GBED and OLWS for $100. These tests can also be ordered individually for $50 each. Testing for both genetic disease and color patterns is key to seeing the big picture and making informed breeding decisions.
24 JULY 2013 PAINT HORSE RACING
capable of producing the splash white phenotype.
The Bottom Line Genetic testing is a valuable tool for making educated breeding decisions. Keep in mind however that all the white pattern genes—including those we can test for and those we can’t— are highly variable in their expres- sion of white. Every day, researchers discover more examples of Paints that test positive for a specific gene with- out expressing a “typical” example of that pattern.
Irene Stamatelakys is a special
contributor for Paint Horse Racing. To comment on this article, email
feedback@apha.com.
Three genes that cause the splash overo pattern were recently identified and can be tested for, though it’s likely other pres- ently unknown genes might also be responsible for the pattern in some cases.
APHA FILE
APHA FILE PHOTO
JESSICA HEIN
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