HYPP & Muscular Health

By: Dr. Lydia Gray

SmartPak strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.

Brief Description

HYPP is a genetic disease affecting Quarter Horses from the Impressive bloodline. This disease causes a dysfunction in how the electrolytes sodium and potassium move in and out of muscle cells. Horses can have one or two genes for HYPP, and thus can show a varying degree of signs, from mild to severe. Mild signs generally include sweating and twitching in the neck and flank, and more severe signs usually consist of muscle trembling and cramping, which can cause the horse to sway or even go down.

Supplements that May Lend Support

Horses that suffer from HYPP may benefit from antioxidants, anti-inflammatories, and muscle supplements specifically designed to help muscle cells recover and rebuild. However, it is very important to maintain a low level of potassium in the diet, so check with your veterinarian before adding any supplement, especially electrolyte, multi-vitamin/mineral and kelp products. Plain salt is an excellent alternative to feeding complete electrolyte supplements, which often contain potassium.

Possible Diagnostic Tests

Because an imbalance in the blood levels of sodium and potassium can only be seen during an episode, horses related to Impressive that demonstrate muscle tremors, weakness or collapse should be DNA-tested for HYPP.

Prescription Medications Available

The medication most commonly used to prevent HYPP episodes is the human drug acetazolamide, which is a diuretic that helps filter potassium from the blood. If an owner recognizes that an episode is about to occur, they can gently exercise the horse or try feeding something with sugar in order to ward off the attack. Veterinarians that are present during an episode may give acetazolamide and other medications intravenously.

Other Management Suggestions

HYPP horses should not be given alfalfa hay, molasses, soybean meal or any other feedstuffs that are high in potassium. Grass hay/pasture, corn, oats, barley, and beet pulp contain low amounts of potassium and are generally safer to feed. Your veterinarian can help you design a nutritional program that is complete and balanced yet contains the minimum amount of potassium necessary. A consistent exercise program is also important in preventing bouts of HYPP.

Questions to Ask Your Veterinarian

  • How do I get my horse tested for HYPP?
  • Should I breed my mare if she only has one gene for HYPP?
  • Is my horse safe to ride once he’s on the medication?
  • Can I continue to trailer and show my horse?
  • Is it okay to have my horse tranquilized for dental and other work?

Additional Resources

Further Reading for You

From our site:
From the SmartPak Ask the Vet Blog:
HYPP (Hyperkalemic Periodic Paralysis)
From The Horse Journal:
  • The Keys to HYPP Are Potassium and Exercise, November 2000
  • Quarter Horses Have Particular Muscular Worries, June 2006

Further Reading for Your Veterinarian

Alberts MK, Clarke CR, MacAllister CG, Homer LM. Pharmacokinetics of acetazolimide after intravenous and oral administration in horses. Am J. Vet Res. 2000 Aug;61(8):965-968.

Spier SJ. Hyperkalemic Periodic Paralysis: 14 years later, in Proceedings. 52nd Annu Conv Am Assoc Equine Pract 2006;52:340-346.

Valberg SJ. Diagnostic approach to muscle disorders, in Proceedings. 52nd Annu Conv Am Assoc Equine Pract 2006;52:340-346.

About Dr. Lydia Gray

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