Hyperkalemic Periodic Paralysis

Impressive, a world champion and sire of world champions, was not effected by the mutation himself. The mutation affected his offspring. "HYPP is the result of the muscles cell's failure to conduct electrical impulses correctly, a process controlled by a protein called a sodium ion channel. This defect leaves the muscle membrane more permeable than normal, allowing sodium to enter the fiber, this disrupts the voltage of cells. Potassium is releases into the blood steam DNA sequences read TTG instead of TTC. Acid Leucine rather than Phenylalanine in the horses sodium channel. Some of the signs that your horses has this defect are muscle weakness, fasciculation or tremors involving all or part of the body., and collapse, episodes may include loose feces, protrusion of the inner corner of the third eye, heaving, sweating, and respiratory difficulty. Attacks can last from a few minuets to several hours. In the worst causes horses can die from respritory or cardiac failure. The gene also causes horses to have bulky muscles, which became fashionable in the show ring. A horse who is HYPP positive or HYPP N/H will have 50% effected offspring and 50% normal offspring. If two positive horses are bred three quarters of the foals will be positive. When a horse has the most severe case it is HYPP H/H. This horse has two copies of the gene. 100% of foals are positive. Testing of these valuable horses at first was dangerous. Vet would give potassium to horses and wait for an episode. Now a simple blood test can be used. Now that the testing was simple and cost only $55 dollars breeders had no excuses not to test. The disorder does not effect horses until after breeding age.

The politics behind this genetic defect are great. Breeders did not want there multi-million dollar horses spotted out as positive. To geld a positive horse, to some, would be to loss a lot of money. In 1990 Impressive himself sold for 1.7 million dollars. Many of the most succesful people in the industry were connected to the Impressive bred horses. HYPP can be handled with special diets and excerise. This fact owners of positive horses thrive on. The American Quarter Horse Association finally took a stand on the genetic defect.

All horses related to Impressive have a notice on there registration papers saying that they have the chance of having HYPP. If your horse is tested N/N, it will replace the notice. The reasoning behind this change is for new horse owners. In 1998 all horses with the line of Impressive must be tested and will be by the Association itself.

Many are glad that the AQHA took a stand on marking papers of HYPP horses. This is because of the reason that of the top 13 stallions 10 are Impressive bred. Some stallions breed 100-150 mares a year. It would only take one generation to stop HYPP and the breeders are not brave enough to stop breeding these horses. There are many reasons not to produce foals that are going to have medical problems. New owners have a right to know if there horse is positive or negative. It is good ethics that a breeder will tell a buyer the truth about there horses problems. I have met people that are more than happy to tell you about their hypp positive horses. Having an HYPP positive or HYPP N/N horse doesn't make you a better person either way. All it shows is that you love the Impressive bred horse and you enjoy this beautiful line.

Questions to think about. . .

Why would a breeder/seller want to keep their horses HYPP status hidden?

Many top trainers are proud to say they don't have an HYPP N/N horse in there barn. Some say that HYPP horses are more muscular although reseach has said different. What do you think?

Do you think that having an HYPP N/H horse is a fad or having an HYPP N/N horse is a fad? Do you think it matters anymore?

What should breeders do with their unwanted HYPP H/H horses? Should they be dumped as grade horses.

Should stallion owners of n/h horses give refunds or rebreeds to n/h mare owners whose mare produced an h/h foal?