Macrominerals: Calcium, phosphorus and magnesium

phosphorus and magnesium are the latest published guidelines for equine ration formulation. Since that time, research has led nutritionists to suggest changes in requirements. Calcium The calcium requirements were estimated for the 1989 NRC publication by the factorial method. The maintenance requirement was estimated and then estimates were added for the amount of calcium needed for fetal growth, milk production or growth of foal to provide requirements for pregnant mares, lactating mares and growing animals, respectively. Maintenance Estimates for maintenance requirements were, for the most part, based on measurements of endogenous losses in feces and urine. The losses were measured with the use of isotopes or by extrapolation from studies in which Ca balances were determined in animals fed a wide range of Ca intake. In the latter case, the endogenous loss was estimated by extrapolating the loss of Ca at zer