The influence of dietary molybdenum on the xanthine oxidase activity of the milk of ruminants.

I . The oral administration of sodium molybdate caused a rapid rise of molybdenum in the milk of cows and goats fed on a low-molybdenum diet, but did not affect the xanthine oxidase activities of the milk of either species. 2. In the milks of cows not dosed with sodium molybdate, the regression of the xanthine oxidase activity ( y ) on the molybdenum content (x) was found to be (r = +0.9386; P c O.OOI), suggesting that all the molybdenum of such milk is bound to enzymically active xanthine oxidase. 3. The molybdenum contents of the milk of goats not dosed with sodium molybdate varied from animal to animal and the xanthine oxidase activities were much lower than those of cow’s milk, There was no correlation between xanthine oxidase activity and the molybdenum content of the milks of the goats. y = 170.7x+43.86