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Determining Parentage DNA testing can be used to match the DNA markers of a horse with one or both of its parents. One or both parents of the horse must be known and they must have a DNA marker report of their own already on file with the registry and/or the lab, in order to perform a DNA parentage verifi- cation test. The results are believed to be more than 99% accurate when a horse’s DNA is matched with both of its parents. Matching a horse’s DNA with only one parent is less conclu- sive, but can still exclude or qualify that parent depending on the DNA match. (Note: “Qualifying” a parent doesn’t guar- antee that horse is the parent, especially if only one parent is tested, but it indicates a high likelihood of that horse being the parent and is generally considered to be a verification of parentage.)


One of the common misconceptions about DNA parent-


age verification is that it can be used to learn the parents of a horse even if they are unknown to the owner. Although it is possible, it’s unfortunately not usually that simple. First, the parent must have been DNA tested previously, and many horses registered before DNA was a common requirement were never DNA tested. Second, if the parent has been DNA tested it is necessary to know which registry and which lab did the test, because results are generally not shared between labs and registries. For example, if the parent was DNA tested at VGL the results won’t be in the database of UK and vice versa. Likewise, if the parent was tested through one breed registry the results are not automatically shared with all breed registries. In other words, there is not one huge universal database containing the DNA results of all horses ever tested. Sometimes, if a person is lucky, a horse of unknown parentage can be tested with a registry and a match will be made, but in most cases it’s like searching for the proverbial needle in a haystack.


Color Testing DNA testing is also popular to test for a horse’s color or to help predict what color foal may be produced from certain pairings. Color testing can be especially helpful in estab- lishing the homozygosity of colors, since this can’t be determined simply by looking at a horse and it can play a crucial role in predict- ing what color foals a horse may produce. Testing for the homozy- gosity of tobiano (pinto) and black are especially popular. A homo- zygous pinto horse will always produce a pinto-colored offspring, and a homozygous black horse cannot produce a chestnut-colored offspring and is more likely to produce a black-colored offspring.


60 July/August 2016


One of the common misconceptions about DNA parentage verification is that it can be used to learn the parents of a horse even if they are unknown to the owner. Although it is possible, it’s unfor- tunately not usually that simple.


Disease Testing DNA testing can also be used to screen for fatal and/or life-threatening inherited diseases such as HERDA (Heredi- tary Equine Regional Dermal Asthenia), GBED (Glycogen Branching Enzyme Deficiency), MH (Malignant Hyper- thermia), HYPP (Hyperkalemic Periodic Paralysis) and LFS (Lavender Foal Syndrome). Although HERDA, GBED, MH and HYPP are most common in the stock horse breeds (Quarter Horses and Paints) and LFS is most common in Arabians, the advances in DNA testing for diseases is still noteworthy to all horse enthusiasts, regardless of breed preference. As people introduce stock horse breeds and/ or Arabians into their Warmblood breeding programs, these diseases could also begin to infiltrate the Warmblood breeding population. HERDA is a great example of how priceless DNA testing


can be. HERDA is a genetic skin disease which usually won’t show symptoms until the horse is around the age of two, and will usually require the horse to be euthanized. By test- ing both parents before breeding, HERDA can be avoided entirely, because as long as one parent is free of the disease the foal will be free of the disease as well. If both parents are carriers of HERDA, however, there is a 25 percent likelihood the foal will inherit the disease, so this heartbreak can be avoided by DNA testing the parents for the disease prior to breeding in order to not breed two HERDA carriers together.


Sezuan’s Surprise I


n 2012 the three-year-old stallion Sezuan, who at the time was believed to be by Blue Hors Romanov, was presented at the Danish 10-day stallion performance test. Owned and presented by international rider Andreas Helgstrand, the young stallion was a star at the testing and was granted his breeding license. As one of the requirements for the Danish breeding approval, Sezuan’s DNA


had to be tested. The spectacular young stallion turned out to not be sired by Blue Hors Romanov at all, but instead was by the stallion Blue Hors Zack. Although it didn’t affect his licensing or approval, the revelation sent the Warm- blood breeding world buzzing and helped to bring the discussion of DNA testing to the forefront.


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