he time has come — you’ve waited 11 long months to meet your foal. Your mare labors normally and has an uncomplicated birth, but something isn’t right. Your newly born foal’s tiny pasterns are like jelly, unable to support his weight, and his skin tears at the touch. Hopeless, he’ll need to be euthanized a few hours after birth. When the results of the genetic testing come back, you learn that he was born with Warmblood Fragile Foal Syndrome, or WFFS.
This dreaded syndrome was discovered 12 years ago but has only been on many breeders' radars since last year after a case of a live foal born with WFFS was widely publicized. Major studs have begun systematically testing for carriers and awareness groups have formed on social media. Prominent stallion owner Paul Schockemöhle, on the other hand, has insisted that cases are exceedingly rare (so much so, that he will pay 10,000 euros to any client who can prove their foal died of WFFS).
The good news is this: WFFS can be prevented.
What is WFFS?
At a simplified level, WFFS is a fatal genetic defect of connective tissue. Disease markers include thin, fragile skin that tears easily and hyperextensible joints. An estimated 6-11% of warmblood horses are carriers of the gene, but WFFS appears to be a recessive mutation, meaning that for a foal to have WFFS, both the sire and dam must carry the recessive gene that causes the defect.
Here’s where it gets a bit more complicated, but stick with me:
A horse that is clear of the mutation bred with a horse that is a WFFS carrier results in a foal that has a 50% chance of being clear of the mutation and a 50% chance of being a WFFS carrier. A horse that is a WFFS carrier bred with another horse that is a WFFS carrier results in a foal that has a 50% chance of being a WFFS carrier, a 25% chance of being clear of the mutation altogether, and a 25% chance of being born with WFFS.
Graphic by Southern Designs. Reprinted with permission.
The message here is clear: the birth of affected foals and reproductive loss due to WFFS is entirely preventable if breeders test their horses and breed responsibly.
A Groundbreaking Discovery
There is no one more educated about WFFS than Nena Winand, DVM, Ph.D, who identified the gene mutation that causes WFFS and subsequently developed the test used to diagnose affected foals and carriers.
In 2007, Dr. Winand was contacted by John Baird, BVSc, Ph.D. from the University of Guelph when a student of his necropsied a warmblood foal that had what appeared to be extreme connective tissue fragility. “[Dr. Baird] wanted to get me in contact with the breeder because they had some questions,” Dr. Winand says. “They were very concerned, of course, because of the potential for [the condition] being inherited.”
The breeder sent Dr. Winand blood samples from the foal’s parents, but at the time, Dr. Winand didn’t have the technology to be able to detect the defective gene from a blood sample alone. She banked the samples and wouldn’t be able to test them for another four years.
In 2011, a similar case was referred to Dr. Winand by Dr. William Miller, a veterinary dermatologist at Cornell University. In this case, the foal was still alive, allowing her to obtain the samples necessary to identify the defect.
“Literally within a day-and-a-half I was able to identify the mutation. It was that simple,” Dr. Winand says. But the response wasn’t what one might expect after such a breakthrough. “When we first developed the test, there was no reaction. No one was testing. Laboklin [Laboratory for Clinical Diagnostics] was offering the test in Germany for years, and nobody was interested, nobody cared.”
The Foal That Sparked a Movement
Although Dr. Winand identified WFFS in 2011, the defect wasn’t widely publicized until the 2018 diagnosis of a Texas-born foal. Southernwood Farm’s Mary Nuttall inseminated her Westfalen mare with semen from a KWPN stallion owned by Van Olst Horses in the Netherlands, brokered via Hilltop Farm, and resulted in a WFFS foal.
The mare had a straightforward birth, but the foal struggled to get up. A seasoned breeder, Mary decided to leave the mare and foal alone for a few minutes to allow the foal to calm down and acclimate to its new surroundings. But when she came back, she was horrified — the foal had large sections of skin missing on all four legs, which had been torn off as the little guy tried to stand up.
“I called my vet immediately, and he came out — we were trying to stop the foal from getting up because his fetlock joints were so lax that they were literally bending backward,” Mary recalls. “But he was very bright, very vocal, you know, desperately wanted to get up and nurse.”
WFFS is characterized by thin, fragile skin and hyperextensible joints. Photos courtesy Dr. Nena Winand.
Mary and her vet pulled milk from the mare and bottle fed it to the foal, then fashioned him splints to help him stand. While they finally got the foal standing on all fours, he would immediately collapse every time he attempted to take a step. The vet suggested that Mary transport her mare and foal to the nearby Texas A&M University Veterinary Medical Teaching Hospital, the nearest veterinary hospital.
“By this time, the foal was getting less and less responsive. He had been absolutely normal response-wise up until that point, but he was starting to slip into a coma, basically,” Mary explains.
On the way back to her farm, Mary received a disturbing call from the vet at Texas A&M. As the vet and his team were lifting the foal onto the X-ray table, a huge section of his skin came off in their hands. They had no choice but to euthanize.
Fortunately, one of the hospital’s vet technicians had previously heard of WFFS, and the vet suggested that Mary send samples to Animal Genetics, a Florida-based lab that performs WFFS testing. After giving the okay to send samples from both the mare and foal, Mary called Hilltop Farm’s Managing Director, Natalie DiBerardinis to break the news.
“I told her what they thought it was, and that we sent samples off to Florida for testing. She said she would open the doors of communication with Van Olst because we both knew that this was going to be like a nuclear bomb going off in the breeding industry,” Mary says.
Hilltop Farm Takes Action
When Natalie answered Mary’s call, the foal had not been given a definitive diagnosis yet. As Natalie and Mary waited to hear back from the Animal Genetics lab, Natalie sent off samples from Hilltop’s own stallions and discovered that the farm had five carriers in their own lineup, including their star stallion, Sternlicht.
“The gut reaction was ‘I need more information. I don’t know enough to even know how to respond,’” Natalie says. “At that point, you’re not only trying to rapidly learn about the mutation, but also trying to figure out the implications for your own breeding program.”
When Natalie discovered that a handful of Hilltop’s top stallions were carriers, the next steps were obvious. “It wasn’t a question of, ‘Do we disclose it?’, it was, ‘How can we try and manage this process when we really don’t have a precedent for it?’ Once we knew we had a carrier, we didn’t feel we could ship semen without disclosing [their WFFS carrier status],” Natalie recalls.
While the long-term impact for breeding programs remains to be seen, Hilltop took a financial hit when they took Sternlicht — one of their top stallions — out of their breeding lineup for a year after he tested positive as a WFFS carrier. While some of Hilltop’s carriers are getting less breedings than they have in years past, that may also be due to a lack of testing by mare owners.
'... we need to be smart, we need to use science ...'
“As things become a little more cohesive across some of the registries, I think we will have a better sense of what WFFS carrier status really does mean in terms of horses,” Natalie says. “You know, we have already seen at the auctions this past year — there was not a difference. They were doing testing and disclosing on stallion candidates at a number of the auctions, and I would not say that there was any difference in sales prices between carriers and non-carriers.”
“People hear about WFFS that aren’t breeders, and even some breeders at this stage, and they assume it’s a disease — they assume something is wrong with the horses. And there is no science that supports that there are any inherent negative qualities to being a carrier — there are no health issues, there are no health risks,” Natalie points out. “I think a lot of the registries have acted very proactively, and now we just want to encourage people to test so that they have more options in the future.”
‘We need to do what is best for our horses’
Today, a growing number of breed societies and registries, including KWPN and Westfalen, require genetic testing and disclosure of WFFS status. Even without this requirement, many breeders are nevertheless testing their stock and supplying carrier information publicly, an action recommended and supported by veterinarians at large. In addition, last November, a European Union directive became law, mandating that a zootechnical certificate (a fancy name for an equine passport) must accompany breeding animals and shipped semen.
Dr. Winand credits Mary for coming forward to the public, triggering a movement for people to start testing their horses. When asked what she would like to communicate to the equestrian community, Dr. Winand said, “We need to cowboy up, understand reality, do DNA tests, use them as a benefit, and move on. It’s simple — we need to be smart, we need to use science, and we need to do what is best for our horses. Inherited defects have been with us since horses were first domesticated and bred.
“The good news is that today we have tools to manage them in order to minimize financial losses and impacts on welfare while we strive to produce outstanding athletes.”