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says Winand. “There is also the emotional and ethical level. All AQHA members should adhere to their breed’s mission statement, to breed healthy horses. We need to understand what we must do to breed healthy horses, and recognize that genetic problems are diseases.”
Dr. Carrie Finno, Assistant Professor and Researcher, Population Health and Reproduction, UC-Davis, does genetic research looking for mutations in horses, to make tests available. “It’s important for new horse owners to understand, especially in the Quarter Horse world, that even if you are not considering breeding your animal, you should do the 5-panel test as part of a pre-purchase exam because many of the muscle diseases can be performance-limiting. They can be managed, but you’ll want to know the genetic status of a horse before you purchase because this is life-long manage- ment. It’s best to go into this with eyes wide open, rather than find out after the fact that the very nice horse you’ve purchased has a problem.”
“Since some of these genetic diseases are not
as common in speed horses new owners may
be unaware of the risks,” says Winand. “Those diseases are still there and could be a huge money loss. Some people say it’s no big deal because you can manage the muscle diseases, which are fairly common in speed horses. Yes, you can, but it depends on what kind of performance level you want. An affected horse will never be good at speed events.” This could be a huge disappointment if you bought a horse to race, or barrel race.
“Someone might buy a horse and not know what questions to ask, like whether it has been tested,” says Dr. Gary Magdesian of School of Veterinary Medicine, UC-Davis. “Ask for test results or do the test for any horse you purchase so you know what you are getting into and whether you want to take it on.”
“Also, for the horse’s sake, you need to know. With some of these diseases the horses need careful diet management. If you take care of them prop- erly, some diseases are manageable with diet and exercise plus medication.
“Testing provides knowledge, and knowledge is power,” Magdesian continues. There is a lot to learn, and most horse owners try to learn all they can about their horses, so they can make the best decisions regarding care and breeding.
LEGAL IMPLICATIONS
There have been several legal issues and lawsuits resulting from situations where breeders were not up front regarding the genetic status of the horses they were selling or standing at stud. Winand testified in a trial in which a major wit- ness wanted people to believe that these genetic problems are not diseases. These types of lawsuits are traumatic and damaging for the breed.
“Money sometimes overshadows ethics,” she says. Horses are sometimes misrepresented if they have popular bloodlines, with owners not wanting
The recessive muscle disorder GBED (glycogen branching enzyme deficiency) has been traced back to the stallion King.
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potential clients to know that those horses are car- riers of a genetic disease.
In this case, the court ruled that the defendants were liable. “Bottom line, if you are doing business in the horse industry, you need to represent the horses accurately, which means you need to see the DNA test results, which are essentially medical records,” Winand says. “If you don’t protect yourself by testing and maintaining accurate records, you can be liable because you are in business, and don’t want the liability that comes from false advertising.”
“It is not advisable to partially advertise DNA test results. You can’t claim that a horse is HERDA- negative, which might be true, and then not disclose that the horse is positive for GBED. That type of partial disclosure could be interpreted as intention- ally misleading advertising.”
“If you have just one horse you might test for everything there’s a test for, but if you have 200 mares you maybe couldn’t afford to,” Winand explains. “This situation, and the fact that stallions tend to sire many more offspring than a mare can produce, even with embryo transfer, makes it to where testing is focused on stallions,” she says.
The ideal situation is when you can do DNA typing at the same time you do these tests. “We’ve known for a long time about HYPP testing fraud and realized we needed a system to DNA-type samples when they come in,” says Winand. “The
5-panel test was based on that premise. We do a DNA type and then all the relevant diseases, even though for some disciplines some of those tests won’t be relevant. AQHA was trying to make the 5-panel test be cost-effective.
These diseases are serious. We must try to avoid them or breed around them so we never create affected offspring.
GENETIC TESTS AID DIAGNOSTICS
“We also use genetic testing for diagnostic purposes,” says Valberg. “It is important to have a veterinarian involved, because you first need to deter- mine if the horse has symptoms that could be linked to the genetic trait. It is important to have a clinical evaluation, and the veterinarian can also interpret results of the genetic test, evaluate clinical signs, and decide whether the problem is actually due to that specific genetic disorder or not.”
Magdesian says most owners test in order to make informed breeding decisions, but another reason is for diagnostic purposes in horses with muscle issues, tying up, poor performance, etc. “This might be a horse that is not performing up to expectations (such as not being able to run the barrels in an acceptable time). If a mare has an abortion, part of the diagnostics would be a test for GBED,” he explains.
Often a genetic disease isn’t the first thing most
EQUINE HEALTH
painting by Orren Mixer