Tuesdays with Tony

This week we’re going to talk about a tough topic: Warmblood Fragile Foal Syndrome. I apologize to those who enjoy my feline brand of sarcasm, but it will be largely missing this week. Even a cat can’t be snarky when it involves death, and Warmblood Fragile Foal Syndrome causes foals to die soon after birth, which is even worse.

What is Warmblood Fragile Foal Syndrome?

Springhill Equine Veterinary ClinicWarmblood Fragile Foal Syndrome (WFFS) is a point mutation in the PLOD1 gene. I’m going to get a wee bit nerdy here because I can’t help myself.  A point mutation means that in the DNA for this gene where a Guanine should be, there’s an Adenine. PLOD1 is responsible for helping raw collagen turn into something that can support all the stresses skin, tendon, ligaments, and blood vessels undergo every day. That single change from a G to an A means the skin can’t handle shear forces. That’s it: one letter. It can also be a cause of abortions in pregnant mares because of umbilical cord ruptures. The umbilical cord grows from the foal side of things, so if the foal has WFFS, the umbilical cord will be made with defective collagen. You know those bubbles you see in a water hose before it bursts? That’s what blood vessels made with defective collagen do. And once the umbilical cord bursts, the foal can’t survive.

I tell you, the more I learn, the more amazed I am that life even happens. There are so many places where one tiny little error makes the whole system fail.

How does my foal get it?

WFFS is an inherited genetic mutation, and specifically an autosomal recessive condition. Every foal gets one copy of genes from the sire, and one copy from the dam. For an autosomal recessive condition to cause problems, the foal has to get two copies of the gene. This is a good news/bad news scenario. It means that most foals won’t be affected with the syndrome. However, autosomal recessive is a great way to have a gene silently make its way into a population.  For example, let’s say we cross a mare that is A/G (this means she’s a carrier) with a stallion that is A/G (so he’s a carrier too). With this cross, there is a 25% chance we get a G/G foal (not a carrier and normal), 50% we get an A/G foal (normal but a carrier), and a 25% chance we get an A/A foal (fully affected). This means it is very, very important to know the status of your mare and stallion if you are breeding!

How do I test my horse?

First, if your horse is a gelding there is no reason to test unless you are curious. WFFS carrier status will NOT affect performance.

Ok, now that that’s out of the way. UC Davis and Etalon Diagnostics are the two places my Docs recommend. Many, many warmblood breeders are testing aggressively right now. This means there may be a wait to get your results, but both labs are trying to get results out as fast as they can. Both labs have submission forms on their websites. You will need to pull about 25 hairs, being sure to get the roots, and mail them in along with the submission form. That’s it.  

And if my horse is a carrier?

That depends on you. Responsible breeding would mean removing carrier horses from the gene pool by not breeding them. I do understand that’s easier said than done. At the very least, avoid breeding two carrier horses. As I said, many stallion owners are trying to determine the status of their horses. Hilltop Farm has done an excellent job getting information to mare owners. They have also said any mares bred to carrier stallions must have proof of non-carrier genetic status. This is a great start. It gives me hope for you humans.

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Until next week,


Springhill Equine Veterinary Clinic

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Tuesdays with Tony is the official blog of Tony the Clinic Cat at Springhill Equine Veterinary Clinic in Newberry, Florida. If you liked this blog, please subscribe below, and share it with your friends on social media! For more information, please call us at (352) 472-1620, visit our website at SpringhillEquine.com, or follow us on Facebook!