Observations on metabolism of selected minerals in the developing horse

Preliminary base values for normal blood and milk composition were obtained from Quarter Horse mares and their foals. These values appeared comparable to those reported in the literature, with the exception of calcium and phosphorus contents which were somewhat low. Magnesium content also was low in the plasma but appeared high in the milk. These figures suggest that there may be a wider range of normal values than has previously been recognized. Radiobalance studies with ⁴⁵Ca, ³²P and ⁶⁵Zn indicated that blood movement and excretion patterns for these ponies were similar to those reported for other species. Distribution studies of ⁴⁷Calcium illustrated the bone-seeking nature of calcium and also the importance of the cecum in the digestive processes of the horse. Mineral composition of tissues and organs of the horse were comparable to similar figures obtained by other investigators with a few exceptions. Some of these exceptions could be explained by con-sideration of age of the animals, while other discrepancies may be attributable to species, ration, and individual differences.