Update on genetic testing in Quarter Horses

Source: Text by Kristy Vanderwende

Genetic Main artWith the ever increasing advancements in equine research, it has become easier than ever to obtain knowledge about genetic disorders that affect American Quarter Horses. In an effort to reduce the likelihood of reproducing genetic disorders beginning in 2015 the American Quarter Horse Association will require all breeding stallions to be five-panel genetic tested before foals are available for registration.

Seasoned breeding managers discuss how genetic testing has impacted their breeding operations and share what visions they have for the future of the industry.

Since 2012, the five-panel test, which consists of Glycogen branching enzyme deficiency (GBED), Hereditary Equine Regional Dermal Asthenia (HERDA), Hyperkalemic Periodic Paralysis (HYPP), Malignant Hyperthermia (MH) and Polysaccharide Storage Myopathy (PSSM1) has been readily available to the public.

Each disease has its own wide ranging effects on the horse, which have caused suffering for those affected as well as significant financial loss and emotional pain for owners and breeders alike.

According to Ladonna Wilkinson, the American Quarter Horse Association’s Senior Director of Registration, the association is making strides toward part of their mission statement to “preserve the pedigree of the American Quarter Horse while maintaining the integrity of the breed and welfare of its horses” with the increase of genetic testing.

“We need to educate, educate, educate,” she says. “We just started requiring the five-panel test for stallions breeding more than 25 mares in 2014, but in 2015 all breeding stallions are required to be tested before the foals can be registered. In the future, we hope that the five-panel test will make people more aware and make a better decision by knowing what they are breeding.”

Conducted at the University of California -Davis, DNA kits are ordered through AQHA by phone or on their online form. Horse owners simply then receive their kit in the mail that is marked for the five-panel, pull the horse hair required and follow instructions to send it back to the lab.

A head shot of a beautiful mare with her foal.“Test results will eventually be noted on the horse’s record,” she says. “We are in the process of updating our system to include all five-panel test results on their online records as well as on the horse’s registration papers when they are reissued for transfer.”

In the case of using frozen semen from deceased stallions, Wilkinson explains that genetic testing can be conducted from the semen itself. She encourages mare owners to call AQHA if they are interested in the results of a particular stallion. This year, many stallion owners are putting the results right on their ads, websites and breeding contracts.

To longtime stallion manager, Kim Dean of Whitesboro, Texas, it is the responsibility of the stallion manager to be open and ethical about their stallions and what mares are allowed to be bred to them.

“We have each stallion’s results right on our contracts,” she says. “We also offer free genetic tests to mare owners. If a mare owner calls and wants to breed and hasn’t had their mare tested then I look at the mare’s bloodlines and look for a potential carrier. If I see anything on there that could possibly match up with a stallion they may want to breed to I have the mares tested before they can be bred.”

Over the past couple of years, Dean has experienced breeders making a lot less of a big deal about horses having positive results and feels the more accepting attitude is a direct result of the increase in education and open information available.

“There are few horses that don’t have any issues,” says Dean. “Some of the best bloodlines that have dominated the industry and made it what is today are carriers of something. At first, I think the emphasis was put mostly on the stallion owner but I have found more mare owners getting more educated.”

Dean encourages mare owners to get their mares tested since it takes two to produce a baby with an issue.

“Even before bloodlines on papers, I think genetic results should be on the horse’s papers. In my opinion, all horses registered should be tested and it should come right with registering a foal,” she says. “It’s the most important thing. This way everybody is on the same page.”

With vast experience shipping semen overseas, Dean has found foreign breeders to be less accepting of carriers of the genetic disorders.

David MassionetteInternational stallion broker and AQHA breeder, David Maisonette of Aurec-sur-Loire, France feels the lack the information in Europe about genetic disorders has caused a negative impact for horses who have a carrier gene.

“At first when people heard the name disease over here they would automatically mark a carrier a no buy or no breed horse,” he says. “For me it is really about the lack of information and people who talk about things that they are not educated about. We should just be happy to have these tests so breeders do not make mistakes.”

For Maisonette who has all of his own mares tested, genetic testing is a real positive for the advancements in more precise breeding. He encourages all breeders to get up on testing and educate themselves to fully understand the disorders. When buying a broodmare, he explains that he would still buy a mare that was a carrier if she had great conformation, show and produce record and was good-minded.

“Excluding all carriers in our breeding program would be the exclusion of amazing horses that we absolutely need to improve our industry. We have used these horses for years why would we suddenly put them to trash?” he asks. “It used to be babies were born dead once in a while and we would say well that’s breeding. Now, we have tests so we don’t make these mistakes.”

In Europe, there is no regulation of not breeding carrier horses as they follow AQHA rules. The German Association Stallion Service Auction does however require all stallions that are entered to be tested.

This year, Maisonette has seen an increase in acceptance of breeding to carrier horses although he does feel negative comments on social networking has not helped speed up the process.

“I would just like people to understand and gain more knowledge about the disorders,” he says. “It’s really all about education.”

Longtime AQHA breeder and stallion owner, Kerry Bradac of Marmarth, North Dakota, has felt for many years now that it is the responsibility of the breeder to have themselves up to speed on testing. She has spent a lot of time educating herself and not only has her stallions tested but all of her mares as well. She hopes for the better of the industry that serious breeders will be most interested in bettering the breed and not just breeding for what will be the most marketable short term.

“My biggest concern is that you have people that have no idea what these diseases mean. You really need to do your research,” she says. “So many great, influential horses in the industry have been carriers. It’s just our responsibility as breeders to know what our horses are so we do not reproduce these disorders.”

As stallion owner, Bradac believes that the stallion’s genetic testing results should be readily available to the public. When she purchased her stallion, Hot Diggity Joe, she had him tested as part of the pre-purchase exam. Although Joe is negative on all five-panels as is her other stallion, Open For Suggestion, Bradac has had all of her mares tested and believes all serious breeders should do the same.

“I think it would be best for stallion owners to ask mare owners if their mares have been tested because it takes two,” she says. “It is unfair for mare owners to say I wouldn’t breed to your stallion because they are a carrier when they are unaware of what their mare is. It’s your personal choice but I think it’s most responsible to know.”

Horse's Mane CloseupAlthough AQHA does not currently require all mares to be tested at this point, many breeders feel it is a responsibility mare owners need to take on as well. According to Wilkinson, AQHA has experienced more mare owners calling and requesting kits and more stallion owners ordering for mare owners.

Longtime stallion owner and breeder, John Wainscott of Georgetown, Kentucky believes if mandatory testing for stallions is required, mare owners should be held to the same level.

“I am not for mandatory testing for stallion owners even though I should be because my horse is negative on all panels,” he says. “As a stallion owner, we are held to a different level. We help with lots of the research that is done so that mare owners can call and ask what the results of our stallion is when they haven’t had their mare tested. There should be as much emphasis on testing for mare owners as there is for stallion owners to be fair.”

As a mare owner, Wainscott has not had any of his mares genetic tested and does not believe panels should determine what horses we breed to each other. He looks for good conformation to be the most important factor when deciding what horses to breed to each other.

“I think it should be optional,” he says. “If you want to have it done and you want to advertise it then you can if you don’t then you shouldn’t have to. I just don’t think what we can do or not do with our horses should be regulated.”

Longtime stallion manager and owner of Pilot Knob Quarter Horses, AQHA judge Mike Hay of Pinnacle, North Carolina has found an increase in potential breeders asking about the status of different horses he stands. He too believes “serious breeders” should go ahead and get their mares tested.

“I’m not sure stallion owners should carry all the weight or responsibility but also I do understand that it is easier to regulate studs over mares,” he says. “The key to me is to educate yourself and make responsible decisions.”

With genetic testing for HYPP already being required for years, Hay hopes the five-panel test will help make progress in “nipping the other disorders in the bud.”

“Everything is so cost involved that you want to give yourself the highest percentage or chance of success whether it’s with breeding, showing or however you are involved,” he says. “I really think everything is headed in the right direction and hopefully in two or three generations we should be able to take care of a lot of it.”

And if the future is any indication of the past, researchers will continue finding more disorders that can be tested to ensure better breeding results.

“I wouldn’t be surprised with the advancements in genetic testing that in 10 years, we don’t have a 10 or even 15 panel test,” Maisonette says. “They will always be finding new diseases. It will always be something.”

GBED is an inherited, fatal condition that generally affects foals under eight weeks of age and mares to abort in utero. It is caused by the body’s inability to properly store sugar. Horses are not able to store enough energy to function properly and often experience symptoms of low energy, contracted muscles, seizures and weakness. An autosomal recessive trait, GBED only affects foals who inherit the disease from both parents. If a horse is a carrier of GBED they will not have any symptoms of the disorder and can not pass it on to their foals unless bred with a carrier.

HYPP is a muscular disease caused by a genetic mutation tracing back to the horse, Impressive. Symptoms include muscle twitching, respiratory noises, and unpredictable paralysis that can be fatal. HH results represent both homozygous positive results. NH are heterozygous horses that can be affected and NN are homozygous negative horses that are not affected by the disorder.

Beginning with of foals of 1998 later required parentage verification of Impressive progeny were required to have a HYPP test at the same time. HYPP has been a required test by AQHA since 2007 where all Impressive progeny were required to be parentage verified and HYPP tested before they were able to be registered. Results are stamped on the horse’s papers. Since then, HH, horses were no longer able to be registered.

HERDA is a genetic skin disease that causes the outer layer of skin to separate, which can cause permanent scarring to the extent that the horse is unable to be ridden. It is believed to be traced back from Poco Bueno’s sire line. Horses must have both parents that possess at least one copy of the gene in order to be affected.

MH is a rare genetic muscle disorder that is caused by an abundance of exercise and stress or can be triggered by exposure to an anesthesia. Symptoms should be treated immediately or results can be fatal. They include sweating, muscle rigidity, increase in temperature, heart rate and high blood pressure. This disorder can be passed on even if only one parent has the defective gene.

PSSM1 causes horses to tie-up with muscle damage where they are unable to move. Horses can be maintained with the condition on a low-starch and low-sugar diet with regular exercise routines. It is a dominant autosomal hereditary condition where both horses with one and two mutant genes are affected. Horses with n/P1 or heterozygous for the disease are affected and have a 50 percent chance of passing it on to their offspring where P1/P1 horses that have two inherited copies have a 100 percent chance of passing at least one copy of the mutant gene on to their offspring.

Ordering Testing Kits It’s simple to test horses for genetic disorders discussed here. Mane or tail hair is submited to a lab. Results are usually available in one to four weeks.

Kits ordered through AQHA are sent to UC Davis for testing and are $85 for members and $125 for non-members. If a panel test is ordered with a required DNA test, the cost is $105 for members (slightly cheaper for both tests) and $145 for non-members. Kits can be ordered by calling AQHA at (806) 376-4811 or can be ordered online at www.aqha.com.

Animal Genetics in Tallahassee, Florida is another lab that also offers five-panel genetic testing for $95 with a one to two day turnaround. For more information on genetic disorders and tests available visit www.animalgenetics.us.



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