The Future of Horses with HYPP

Letter to the Editor:

This letter must begin by saying how proud I am of a man whom I have never met.  His name is Steve Stevens of Houston, TX, the current president of the American Quarter Horse Association (AQHA).  Mr. Stevens has given the membership of AQHA a voice.  He has written personal letters of his activities as president and the goals of the Executive Committee, available on the AQHA website at

He has given us a vision to expect AQHA to “To record and preserve the pedigrees of the American Quarter Horse while maintaining the integrity of the breed,”—the very specific mission statement of AQHA written in 1940.

On October 17, 2003, Mr. Stevens published a letter to the membership of AQHA with the activities of the Executive Committee on October 7, 2003.  One of the most explosive issues in the Quarter Horse history was a major topic during this meeting and from it came the following proposal:

“The next important topic relates to Hyperkalemic Periodic Paralysis (HYPP).  The stud book and registration committee has asked the executive committee to obtain input from the membership regarding this important matter that will appear on their agenda at the Reno convention in March 2004.  The proposal is as follows:

1. Rule 227 will be amended making foals of calendar year 2006 and after ineligible for registration if they are descendants of the stallion Impressive, AQHA Number 0767246, and found to be HYPP positive (H/H). 
2. Additionally, Rule 227 will be amended to provide that foals of 2010 and later that are found to be HYPP (N/H) will only be eligible for registration as geldings or non-breeding mares.

Again, make your elected representatives and AQHA staff aware of your feeling regarding this issue.”
The Executive Committee recommended this proposal in the December 2003 issue of the Quarter Horse Journal, and stated that it would, in fact, be on the table as a recommendation for the Stud Book and Registration Committee during the March 2004 AQHA Convention to be held in Reno, NV.

Quickly, the proponents and opponents of HYPP, a devastating genetic disease  perpetuated in the halter horse industry, shared their voices with Mr. Stevens and AQHA.  During the AQHA World Show in November 2003, a halter task force of trainers and breeders met with Mr. Stevens and the Executive Committee.  A new proposal was written and a new letter by Mr. Stevens appeared on the AQHA website, November 12, 2003:

“Based on this discussion, the subcommittee will recommend the following to the entire stud book and registration committee during the 2004 AQHA Convention in Reno:

1) Foals of 2006 and later tracing to the stallion Impressive will be required to be parentage verified and tested for HYPP.
2) Foals of 2006 and later testing positive for HYPP (H/H) will not be eligible for registration with AQHA.
3) Foals of 2024 and later testing positive for HYPP (N/H) will not be eligible for registration with AQHA.
In addition, the subcommittee supported a recommendation made by the executive committee to commence an education and awareness campaign informing the membership of the effects of HYPP.

I hope our members believe this to be a workable solution to this long-standing matter of importance to our association.  If passed at the convention, this resolution should ultimately eliminate the problems associated with HYPP, while being fair and equitable to our members who presently own these horses.”

Evidently, the second proposal will be the one on the table at the AQHA Convention in March 2004.  There was not time between the November date and the publication of the Quarter Horse Journal to print a retraction.  Therefore, many subscribers of the Quarter Horse Journal think that the first proposal is going to be the recommendation of the Executive Committee to the Stud Book and Registration Committee for a rule change.

This brings a monumental outcry from the members of AQHA who are ultimately concerned for the well-being of our beloved and chosen breed.

The American Quarter Horse Association describes HYPP as follows:

Hyperkalemic Periodic Paralysis. An inherited disease that leads to
uncontrolled muscle twitching or profound muscle weakness, and in
severe cases, may lead to collapse and/or death.

An organization called the N/N Alliance Breeders Association has been formed to address HYPP rule changes and public education with AQHA at the 2004 convention.  It is our primary goal to support Mr. Steve Stevens and the Executive Committee with the first proposal that was written and published in the Quarter Horse Journal.

The N/N Alliance has a web site to inform and support AQHA through this time of transition away from HYPP:

There is an online petition at the following web site:

The N/N Alliance has thoroughly researched HYPP.  We are giving a voice to the rank and file members of AQHA and other stock breed associations that also have registered descendants of Impressive.  HYPP problems affect the American Paint Horse Association, the Appaloosa Horse Club, Palomino Horse Breeders of America, and now the Half Arabian Registry.  The American Quarter Horse Association is responsible for the initial funding of HYPP research, accurate testing procedure, initial HYPP rules and regulations, and the spread of HYPP to the other stock breeds.  AQHA now becomes responsible as the forefront of rule changes for the eradication of this genetic disease.  The N/N Alliance is hopeful that the other stock breed associations will follow the AQHA lead.

We received this email from Dr. Sharon Spier, University of California at Davis, the predominant genetic expert on HYPP:

From : Sharon J Spier
Sent : Sunday, 14 December 2003 3:08:03 p.m.
To : "Diane"
Subject : Re: HYPP Testing

Dear Diane, Thank-you for your question. I will try to explain. The
genetic test is not specific for Impressive or any other bloodline.
The test is 100% accurate for the mutation that causes HYPP, and to
date, only this mutation, and the disease, HYPP, have been
identified in descendants of Impressive. The test was validated in
this bloodline, because that is the bloodline where veterinarians and
horse owners world-wide were seeing disease. We have not been able
to trace the mutation further in the Quarter Horse breed, but if the mutation
arose from parents of Impressive, then we would be able to detect it.

In humans, and theoretically in horses, other mutations in the sodium
channel could cause HYPP. We have not experienced this in horses
(that veterinarians have seen HYPP in other bloodlines). If this
occurs in the future, then sequencing studies could reveal another
mutation and another test could be developed. The test identifies
the specific genetic mutation that causes an amino acid substitution
in an important portion of the skeletal muscle sodium channel.

I hope this helps. Let me know if anything needs to be clarified
further. This disease is not good for the overall health of the
horse. If people would just see this, then I don't think there would
be so much controversy.

Sharon Spier, DVM, PhD

Conclusive evidence of a stock breed association that has chosen to decline registration to HYPP positive horses is the Appaloosa Horse Club of Canada (ApHCC).  This club sent the vote to its membership.  90% of the ApHCC members returned their ballots with an 85% vote in favor of the following rule change:

C. Genetic Disorders
1. Effective 01 January 2000, any horse applying for identification or registration in the Register of Appaloosa Horses and carrying a known and/or identified genetic disorder, including, but not limited to HYPP (Hyperkalemic Periodic Paralysis) and SCID (Severe Combined Immunodeficiency), shall only be eligible for entry into the Register of Appaloosa Horses upon receipt by the ApHCC of Application for Pedigree Registration/Identification and veterinary  verification that the horse is a gelding or spayed mare.
2. Effective 01 January 2002, any horse applying for identification or registration in the Register of Appaloosa Horses and carrying a known and/or identified genetic disorder, including but not limited to HYPP (Hyperkalemic Periodic Paralysis) and SCID (Severe Immunodeficiency), shall be denied identification or registration with the ApHCC.

AQHA halter trainers and breeders have asked for 20 years to end the breeding cycles of HYPP-positive horses. Twenty years will see approximately eight additional generations of HYPP positive horses, which could mean another 100,000 horses affected by HYPP.  It is a well-known fact that the practice of halter breeders is to breed N/H to N/H and H/H to N/N, increasing the chances of having positive foals.  It is their premise that HYPP N/H and H/H horses are more competitive in the show pen. 

When asked “Why HYPP?” there have been two answers from the proponents of HYPP:

1. It is my right and choice as a breeder to breed what I want.
2. I have investments and investors in my business practices that require the breeding of HYPP into halter show horses that win.

The argument that the halter task force members presented to AQHA is that they will be hurt financially if they lose breeding monies from their HYPP positive horses.  They want the time to retire from the business before HYPP can be eradicated.  The second argument is that their horses are treated with medicine that relieves symptoms.

AQHA has years of history promoting the Quarter Horse internationally.  It will not benefit AQHA to continue promoting the Quarter Horse that needs a dominant genetic disease to be the consummate halter horse.

The halter industry represents about 2% of the Quarter Horse industry.  In years past, halter horse classes were large, well-attended, well-respected events.  In years present, the halter horse classes have decreased in size, are rarely attended by many spectators, and have lost much respect in the public arena.  The present day halter horse is not a horse that the average AQHA member can own, care for, and show. 

Halter and HYPP have become big business for a few select trainers, and the rank and file members of AQHA have flown to events more friendly to their ownership.  Plus, our members are hurt physically, financially, and emotionally with nondisclosure, deaths of horses, and injuries to humans due to HYPP positive symptoms and effects. 

For halter horses to be “the best of our breeding stock,” it has been disappointing that AQHA has popularized the HYPP-positive horse.  I personally believe that AQHA thought its members would voluntarily breed out the HYPP-positive horses in breeding programs with proper education supplied by AQHA research dollars.  Rather than move away from this disease, the halter horse industry grasped it and flaunted it.  Now, it is up to our association to regulate the eradication of HYPP in our beloved and chosen breed.

HYPP is 100% preventable.  UC Davis and other laboratories have a 100% accurate test using blood or DNA from the roots of mane hair.  AQHA is proposing to stop breeding positive-HYPP horses to eradicate this genetic disease in future generations, and to prevent the possibility of suffering and death from this terrible disease.

I own and breed halter horses and all-around performance horses.  I chose from the onset of information about HYPP to avoid owning and breeding HYPP positive horses; and I love the HYPP N/N Impressive lines.  I fully support AQHA President Steve Stevens and the AQHA Executive Committee in their first proposal for the eradication of HYPP in the AQHA registry.  I firmly believe that all members of AQHA should have a voice in this decision.  The reputation of the American Quarter Horse is not to be manipulated.

Vicki Hittson
N/N Alliance Breeders Association

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More