Potassium, the third most abundant mineral in the body, is the major cation in intracellular fluid. Forages are excellent source of potassium, usually containing 1 to 4 %. In fact, high potassium content in lush, spring pastures seems to be a major factor associated with grass tetany. The apparent absorption of potassium from alfalfa clover and cabbage varied from 87-94%. Potassium absorption from a mixed pea and oat silage was lower and addition of concentrates including barley further decreased the potassium absorption. Potassium is excreted from the animal body primarily in the urine, theretofore urinary excretion and apparent absorption are effective parameters for the estimation of bioavailability.
As forages mature and the potassium content decreases, low concentrations of potassium are observed in weathered range forage. Cereal grains also are often deficient in potassium and high-concentrate diets usually require potassium supplementation unless a high-potassium forage or protein supplement is included in the diet. While oilseed meals are good sources of potassium, it can also be supplemented in cattle diets as potassium chloride > potassium bicarbonate > potassium sulphate or potassium carbonate.