NRC gives formulas for calculation of the requirements for calcium (Ca), phosphorus (P), magnesium (Mg) and potassium (K). The roughages and concentrates which are used in regular horse feeding contain sufficient potassium to prevent deficiency occuring. We will from 2012 nevertheless include potassium in the analyses of nutrients in the feeds shown in PC-Horse, since K is an important cation which is required for calculation of the cation-anion balance of a ration.
Calculations of mineral requirements for maintenance are generally based on endogenous losses and the efficiency of absorption of the nutrient in question. For exercising horses, mineral requirements are related to energy requirements. In addition, for young horses the formulae contain a component which relates mineral requirement to kg weight gain.