Posted 3/1/2004

In 2003 the first widespread news of a devastating dermal disease in Quarter Horses, known as Hereditary Equine Regional Dermal Asthenia (HERDA) or Hyperelastosis Cutis (HC), began circulating primarily on the internet, mostly in chat rooms. Soon, the Quarter Horse News and other publications were running a few articles on the disease but not yet revealing the sireline associated with it. Research was ongoing at Mississippi State University, Cornell University, and at University of California, Davis. Yet, on contacting these facilities and requesting more information everyone was mute as to which sireline was the origin of this disease.

Our own research and communication with those with first hand experience with the disease let to the possibility that Doc O’Lena was the most probable source. But until Ann Rashmir, associate professor of surgery and head of the Hyperelastosis Cutis Research Program at Mississippi State University, and Nena Winand, a geneticist and assistant professor in the Department of Molecular Medicine at Cornell University, broke their silence in an interview for an article with "TheHorse.com" published a few days ago, no one knew with any surety what the sireline was.

It has now been established by these researchers that Poco Bueno himself is the source of this genetic disease. And, if the inheritance is a simple single recessive gene he would have theoretically passed it on to 50% of his offspring. Three of his well known sons that have been confirmed to be carriers are, Doc O’Lena, Poco Tivio, and Dry Doc. Theoretically the most prevalent carriers of this disease will obviously be intensely linebred Poco Bueno horses.

How does this affect the Foundation Quarter Horse Association and it’s members? Not as severely as one might first assume. As most of you know, at FQHA, we have never promoted a single foundation Quarter Horse bloodline over another. FQHA and it’s official publication, Foundation Quarter Horses Magazine have searched for living descendents of, and promoted all top Foundation Quarter Horse lines, for a number of years now, through the Magazine’s "Best of the Best" series. For this reason, FQHA as a whole has registered a broad spectrum of foundation Quarter Horse bloodlines which do not trace to Poco Bueno . . . Foundation sires like: Bert, Bill Cody, Blondy’s Dude, Blue Valentine, Cutter Bill, Continental King, Driftwood, Harlan, Hollywood Gold, Jackie Bee, Joe Cody, Joe Hancock, King, most King Ranch Sires, Mr Gun Smoke, Mr San Peppy, Oklahoma Star, Pacific Bailey, and Skipper W, just to name a few. In fact, on close analysis of FQHA registered horses, only 2.07% of FQHA horses are either sons, daughters, or grandget of any of the four KNOWN carriers of HERDA (Poco Bueno, Doc O’Lena, Poco Tivio, and Dry Doc). A grandson or granddaughter of a carrier would have a theoretical 25% chance of being a carrier themselves. But that also means that the odds of NOT being a carrier of this disease would be 75%!

Yet, it is difficult today to find a horse that does not descend from the legendary Poco Bueno. So, to put things in perspective, if your horse is a great-grandson or great-granddaughter of Poco Bueno, Doc O’Lena, Poco Tivio, or Dry Doc, (or any other known HERDA carrier) and there were no other crosses to any of these sires, your horse would have only a 12.5% chance of carrying the gene for HERDA (assuming it is a simple single recessive gene). If you horse is linebred to any of these horses extensively then, of course, the chances of your horse being a carrier would be increased.

The key to management of this situation is a reliable test for the gene being available as soon as possible. 1) As soon as a test for the gene associated with HERDA is available, the Foundation Quarter Horse Association will require a negative HERDA (HC) test for all descendants of a HERDA effected line before they can be registered with FQHA. At this time this includes horses descending from Poco Bueno, and his dam Miss Taylor. 2) If your horse is a Poco Bueno or Miss Taylor descendent and is already FQHA registered, you will be required to provide the association with a negative HERDA test before any offspring of that horse can be FQHA Registered.

Just as with other genetic diseases and defects such as HYPP, LWOG, cryptorchidism and parrot mouth, we (FQHA) are striving to preserve the BEST of the foundation Quarter Horse and feel that as an association, we, and our members, must behave responsibly in this matter.

Sincerely,

Theresa Ann Warden, Secretary, Foundation Quarter Horse Association