Know Your Genes: How Ranches Handle Genetic Testing

By Abigail Boatwright

When it comes to breeding horses, the more information you have about the sire and dam, the better chance you have of producing a healthy and successful foal. Testing the DNA of equine individuals for certain genetic disorders before buying or breeding adds an important layer to that decision-making process. AQHA offers a five-panel genetic test for the most common hereditary disorders, and in 2015, the Association began requiring all breeding stallions to be tested.

We spoke with three AQHA Ranching Heritage Breeders about how the advent of genetic testing has changed their management, marketing and breeding decisions.

Garth Gardiner of Gardiner Quarter Horses in Ashland, Kansas, comes from a long line of Angus breeders. He has been familiar with genetic disorders and genetic testing in the cattle industry for years, so the adjustment to genetic testing in horses wasn’t a stretch.

HERDA Genetic Disorder

HERDA is a skin disorder characterized by hyperextensible skin, scarring and severe lesions along the back of affected horses. The condition is most commonly seen in horses in cutting and cow horse disciplines because, according to research done by Dr. Ann M. Rashmir-Raven and Dr. Nena J. Winand, the mutation can be traced to Poco Bueno’s lineage. But a horse that is a carrier shows no signs of the disorder; it’s only when the horse has two copies of the gene that this devastating skin condition is expressed.

Because these ranch breeding operations focus on horses with cow sense, of the five mutations that are tested for, they’re most concerned with HERDA.

“From a management standpoint, you have to pay attention if you have a carrier of a mutation like HERDA,” Garth says. “I haven’t been overly concerned if there’s a horse that carries HERDA, I just know we need to manage it carefully – it wouldn’t be a good idea to breed that horse to another carrier.”

J.D. Wing of Tee Cross Ranch in North Pueblo, Colorado, says the importance of five-panel genetic testing is similar to the advent of testing for HYPP a couple of decades ago.

“If we test a horse and we have an N/H horse (a carrier), then we are going to breed to an N/N (normal) horse,” J.D. says. “We are not going to roll the dice and breed an N/H horse to an N/H horse at all.”

Right now, J.D. has just one really good mare that’s a carrier, and he says after he began testing for genetic disorders, he gradually weeded out carriers from his broodmares.

“If I had two mares that are comparable, I’m always going to choose the N/N mare for the progression of the breed,” J.D. says.

GBED Genetic Disorder

Chad Smith at O RO Ranch in Prescott, Arizona, says he’s focused on cleaning up his breeding stock to be free of markers of genetic mutations – primarily, GBED, which is fatal in newborn foals and caused by a defect in glycogen storage that affects the heart, skeletal muscles and brain. It’s inherited as a recessive gene, so only a horse with both copies of that gene will express the disorder.

“Once you breed one carrier to another, that could end up with a fatality, and that affects our numbers, so now we test everything,” Chad says. “It’s a requirement for us now. But not many people are asking for us to do it yet for ranch-type horses. We are definitely paying attention to these tests, and we won’t buy any more stud prospects that are not clean.”

PSSM1 Genetic Disorder

Even for working stock, Chad says it’s important to make sure your horse doesn’t have PSSM1 – a muscle disorder that causes muscle pain, stiffness, skin twitching, sweating, weakness and a reluctance to move – some refer to these symptoms as “tying up.” PSSM1 is a dominant gene where sometimes even a carrier can exhibit the disorder.

“For ranch horses, you’ve got to have a really hearty, longwinded, tough horse for a lot of situations, and having one that ties up, that’s not going to work well,” Chad says.

Genetic Testing and Management

Because all of Gardiner Quarter Horses’ broodmares have been tested and are negative for HERDA, Garth says he’s not worried about whether a stallion is negative or a HERDA carrier.

“I’m more concerned about producing a marketable product, and the offspring that we cross our mares with,” Garth says. If one of Garth’s mares was bred to a stallion whose five panel genetic test is negative across the board, he may not always test the foal.

“It’s really not worth the extra money when you can expect those offspring to be negative, as well,” Garth says.

However, he doesn’t hesitate to test a foal he’s bred if the stallion is a carrier.

Once horses bred on the Tee Cross Ranch are ready to ride, they’re sorted into either J.D.’s performance horse line or his ranch horse line. He says he keeps tabs on the sire and dam’s genetic status, but doesn’t test the ranch horses as much. The performance horse prospects of any sex are always tested, and J.D. advertises their results regardless. J.D. has mares tested before they’re placed in the broodmare barn, or when he’s prepping a horse for sale. Or, if he’s preparing a Snaffle Bit prospect as a 2-year-old, he’ll have the testing done.

Chad pulls hair from his horses to test when he halter breaks them at 6 to 8 months of age. If a horse is destined to be a gelding, he won’t test it.

“Then we know going down the road with training, what we want to do, and if we want to spend a lot of time for ourselves on them for blood stock,” Chad says.

Chad says knowing the genetic status of his horses has helped him make better breeding decisions and get a better foal crop. 

Gardiner Performance Horses previously stood Hes Wright On and Hickory Holly Time. They both had negative five-panel tests, which Garth says slightly helped with mare owners looking for a stallion for breeding.

“If your stallion is not a carrier, it also gives you a larger pool of mares to select from,” Garth says. “Some owners may have mares that may be a carrier, and they don’t want to breed to a carrier, so they’re looking for a stallion that is not a carrier.”

For Garth, a stallion’s test results are not the main thing he evaluates when seeking out breeding stock, particularly because he only keeps mares that test negative.

“I think it all plays into a larger selection process,” Garth says. “I think it’s one of the ingredients, but I don’t think it’s the most important ingredient.”

When marketing in the breeding business, Garth says you need to disclose if your horse is a carrier, but he doesn’t think being a carrier for HERDA is always a bad thing. In fact, a study published in 2009 by Dr. Rashmir-Raven and her team hypothesized that carriers of HERDA in the cutting industry may have a performance advantage.

As an experienced breeder, Garth says it’s his job to inform potential buyers and breeders of his horses’ genetics.

“When someone purchases a horse from me, they’re not going to have any problems (with genetic disorders) from us,” Garth says. “Or, if they do purchase from someone a horse that is a carrier of HERDA, provided it’s a breeding animal, they need to understand that you don’t breed a carrier to a carrier. But that’s not a big deal, there are plenty of great non-carrier stallions out there – you can find non-carrier sons of really great stallions that are carriers.”

When J.D. is looking to purchase broodmares, he wants to know the genetic test results.

“I want to know if they’re a carrier for HERDA,” he says. “If that information is not listed, it’s one of the first questions I ask. If they haven’t tested, I’ll ask if they’re going to do it before the sale. When you’re talking about spending $15,000 to $20,000 on a mare, the last thing you want to do is invest $150,000 buying a bunch of mares, and all of a sudden, you can’t breed them to one of your stallions that you were planning to breed them to.”

Chad requests testing by sellers before purchasing breeding stock.

“I have offered to pay for the test for some sellers, if they’ll hold the horse for me during the period waiting for the results,” Chad says. “You’re better off to be out that fee, versus spending a lot of money you’re spending on the horse, only to end up with a good gelding you can’t breed.”

Know Your Breeding Stock's Genetics

Garth says the more information you have about your breeding stock animals, the better breeding decisions you can make.

“I think the $100 cost to do the five-panel test is a wise investment in your program to have that knowledge and make wise management decisions when making those breeding choices,” Garth says.

Before genetic testing was so prevalent for horses, Garth purchased a mare from a sale that hadn’t been tested, and as he says, he “made a poor decision.”

He bred her to a HERDA carrier and then a test of the foal showed that the foal possessed both copies of the gene, meaning it would be affected by the mutation. Rather than wait to see if the horse would succumb to the painful and career-ending conditions (the lifespan of most horses living with HERDA is only two to three years), he made the difficult decision to euthanize the colt.

“I made a breeding mistake,” Garth says. “I wouldn’t want to sell someone a really nice colt and try to hide the fact that he’s not only a carrier of HERDA, he has both sides of the gene and more than likely would exhibit the disorder at some point in his lifetime. So that was the only sound decision I could make.”

This experience is why Garth feels it’s so important to familiarize yourself with your mare’s pedigree and see if there are any horses in her lineage that could contribute to her possessing genetic mutations.

“If the horse could be a carrier, I think it’s wise to invest your money in the five-panel test,” Garth says. “It’s a minimal investment compared to going through the process of breeding a mare, maybe even paying for a recipient mare, embryo flushing and transfer – the list goes on … and then finding out that you’ve got a carrier. All of that is way more expensive than the $100 for the five-panel test.”

J.D. recommends educating yourself on the mutations covered by the five-panel test.

“Once you understand what they’re testing for and why, figure out what you’re OK with,” J.D. says. “There are a lot of people fine with (having) a (HERDA) carrier. I don’t mind a carrier horse, but if you’re going to have one, you need to understand what the risk is, and that it limits you, especially for breeding purposes.”

Chad advises aiming for a clean five-panel test result on horses you keep in your breeding stock.

“Having a carrier is manageable, but for me, I would try to stay away from it,” Chad says. “To me, it’s cut and dried.”

About the Sources

Garth Gardiner is a fourth-generation rancher from Ashland, Kansas. Together with his brothers, he operates Gardiner Angus Ranch, which was established in 1885. Garth and his wife, Amanda, started Zoetis Ranching Heritage Breeder Gardiner Quarter Horses (gardinerquarterhorses.com) in 1999. The ranch produced 2014 NRCHA Open Derby Champion Hickory Holly Time, 2013 NRCHA Level 1 Open Futurity winner Cutting Wright Up and 2014 NRCHA Open Hackamore winner Time For A Diamond.

J.D. Wing is the foreman at Zoetis Ranching Heritage Breeder Tee Cross Ranches (teecrossranches.com) in North Pueblo, Colorado. The ranch was founded by AQHA Past President Robert C. Norris, and the Tee Cross brand was the first brand registered in Colorado.

Chad Smith is ranch manager at O RO Ranch (facebook.com/O-RO- Ranch-286142514849200) in Prescott, Arizona. The Zoetis Ranching Heritage Breeder has bloodlines tracing back hundreds of years in Mexico, and its horses were included in AQHA’s original breed registry in 1940. The O RO Ranch-bred foundation mare MC’s Lone Wolf, the dam of Arizona Junie, sire of American Quarter Horse Hall of Famer Fillinic. The ranch spans 257,000 acres of some of the country’s more remote areas, and O RO Ranch’s horses are bred to work the rugged area’s sometimes-wild cattle. O RO Ranch’s horses have also gone on to influence in the performance horse and professional rodeo world.