Potassium is the most abundant intracellular electrolyte in your horse's body, critical for muscle contraction, heart rhythm, nerve signaling, and maintaining proper fluid balance. It works in concert with sodium to create the electrical gradients that power every nerve impulse and muscle contraction. Fresh pasture and hay are naturally rich in potassium, so deficiency from diet alone is uncommon. However, horses lose significant potassium through sweat during exercise and hot weather, and this loss can impair muscle function and recovery.
A 500kg horse needs about 25 grams of potassium per day — roughly the weight of two tablespoons of salt. Grass hay provides approximately 10 to 25 grams per kilogram of dry matter, so a standard hay ration easily meets this need. Working horses may need an additional 10 to 20 grams through electrolyte supplementation after heavy exercise.
1.4% of daily nutrient intake
Potassium makes up 1.4% of your horse's total daily nutritional requirements by weight.
Muscle weakness, fatigue, reduced exercise tolerance, decreased appetite, and in severe cases, heart rhythm irregularities. Potassium depletion is most likely in horses sweating heavily during prolonged exercise or hot weather without adequate electrolyte replacement.
Excess potassium from forage is efficiently handled by healthy kidneys. Horses with hyperkalemic periodic paralysis (HYPP, a genetic condition in certain Quarter Horse lines) must be on strictly potassium-controlled diets, as excess triggers dangerous muscle spasms and collapse.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 25 | 50 | g | For a 500kg horse. Hay is naturally rich in potassium, so dietary deficiency is essentially impossible from forage alone. |
| Working / Active | — | 35 | 70 | g | Working horses lose significant potassium in sweat. Electrolyte supplements after exercise help replace losses. |
Source: NRC 2007
