Fission products and the dairy cow. 2. Some aspects of the metabolism of the alkaline-earth elements calcium, strontium and barium.

Ca45 and Sr89, Sr89 and Ba140 or Ca45 and Ba140 were administered simultaneously, both orally and intravenously, to pairs of lactating cows. Data are presented on the mean recoveries during eight days following administration of the isotopes. Calculations of individual discrimination factors indicate that absorptive discrimination made the most important contribution to over-all discrimination between calcium, strontium, and barium during their passage from diet to milk. Mammary secretion significantly influenced strontium discrimination. Renal excretion. endogenous secretion into the gut. and mammary secretion were approximately equal for barium. Finally, the metabolism of Ca45, Sr89, and Ba140 in the cow is discussed and data are compared with those on rats.