Changes in the absorption rate and tissue distribution of zinc under different nutritional status of this element were examined. Five-week-old male Wistar rats were given a zinc-deficient basal diet (zinc content, 0.6 ppm) or the basal diet supplemented with graded levels (5.5 ppm, 10 ppm, 15 ppm, 20 ppm, 30 ppm or 40 ppm) of zinc as zinc sulfate for 4 weeks. Feeding of zinc-deficient diet for 4 weeks induced poor growth and a significant decrease in zinc concentrations in many tissues. Rats fed a diet containing zinc at a level of 5.5 ppm showed lower growth and tissue zinc concentrations than those fed diet containing zinc at level of 10 ppm or more. In particular, the zinc concentration in tibia responded remarkably to the elevation of dietary zinc level. Apparent absorption of zinc was inversely correlated to the dietary zinc level; apparent absorption in rats fed diet containing 5.5 ppm zinc was 92%, while that in rats fed diet con.taining 30 ppm zinc was 27%. These results indicate that the minimum dietary requirement for zinc is 5.5 to 10 ppm in growing rats.
