Abstract
The effects of zinc deficiency on the responses of rats in selecting dietary protein were investigated in growing rats. Two diets of 10% and 20% demineralized soy protein were given simultaneously to rats for 11 days after feeding then with either a zinc-adequate (25ppm Zn) or a zinc-deficient diet (≤0.3ppm Zn) for 10 days. Rats in the zinc-adequate group selected the 20% protein diet more frequently than rats in the zinc-deficient group. No differences were found between zinc-adequate and zinc-deficient rats in selecting the 10% protein diet. Zinc-deficient rats showed a reduced tendency to select the 20% protein diet. When zinc-deficient rats were offered a choice between 0% and 20% protein diets, they ate preferentially the non-protein diet 9 days after presentation of the diets. Zinc-deficient rats that selectively fed on these diets survived longer than those that fed on either the 0% or 20% protein diet alone. Serum alkaline phosphatase activity and the femur zinc concentration in zinc-deficient rats were decreased to a lesser extent in the group allowed to select the diet than in the group given the 20% protein diet. These results suggest that rats may regulate their intake of dietary protein to maintain their body zinc status.
