Hyperkalemic Periodic Paralysis (HYPP)

Performance Horse Nutrition

Hyperkalemic periodic paralysis (HYPP) is a co-dominant single autosomal gene disorder that primarily affects Quarter horses. In the muscle cells of horses with HYPP, regulation of the movement of sodium and potassium to and from cells is disrupted. This can result in repetitive muscle contractions and in severe cases muscle fasiculations. These are usually first evident over the rib cage and flank areas, but may spread to other muscle groups. The most important management practice for HYPP positive horses is to limit the dietary intake of potassium to less than 1% of the total diet. The largest source of potassium in the diet of a horse is grass and hay. Forages can contain over 3% potassium, factors such as moisture content, stage of maturity and variety (legumes contain more than grasses) all effect forage potassium content. Grains also contain potassium but at a lower rate usually less than 0.5%. When developing a feeding regime for these horses grass hays or pastures such as Bermuda grass, prairie hay, or timothy should be used as a forage source instead of legume hays such as alfalfa. The use of cereal grain as a major portion of the diet will reduce the potassium concentration of the diet. Beware of commercial feeds containing high amounts of molasses, soybean meal, or dehydrated lucerne as these all have relatively high potassium concentrations (greater than 2%).

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