Horses with hyperkalemic periodic paralysis (HYPP) need careful dietary management to reduce or eliminate its characteristic muscle dysfunction attacks. While diet won't eliminate all signs, it can make an affected horse more comfortable and useful, and even save his life.

HYPP is a genetic muscle disorder tracing back to the Quarter Horse stallion Impressive, although not all descendants have the disease. Genetic testing is highly recommended and is almost 100% diagnostic. A horse can show clinical signs even if the problem is inherited from only one parent.

The HYPP genetic defect disrupts the function of tiny gateways in muscle cell membranes called sodium channels. Instead of opening and closing normally, they stay open during an HYPP episode, allowing an uncontrolled flow of sodium ions into cells. Normal functioning of the cells is altered, which results in the signs of HYPP–weakness, muscle twitching, shaking, trembling, and paralysis of muscles in the upper airway. The most severe threat to these horses is death from heart failure.

Potassium is linked to clinical signs, so Judith Reynolds, PhD, PAS, an equine nutritionist at ADM Alliance Nutrition, who has researched feeding HYPP horses, offers this advice: "To reduce episodes, it is important to limit the amount of potassium fed in each meal