Changes in Plasma Zinc Related to Fasting and Dietary Protein Intake of Japanese Quail 1

Summary

Day-old Coturnix coturnix japonica of both sexes were fed a purified diet containing deficient, requirement, or excess amount of zinc (7, 25, or 75 mg of zinc per kg of diet, respectively) for 4 wk. The plasma zinc concentrations reflected the level of zinc intake during this time. All birds except non-fasted controls and one group of supplemented birds were fasted for 24 hr. There was no decrease in plasma zinc in the deficient birds after fasting; however, there was a significant decrease in birds receiving 25 or 75 mg of zinc per kg of diet. Following the fast, supplements consisting of complete diets or dietary components were fed, with or without added zinc (75 mg of zinc per kg of diet) for 4 hr. In birds that had received normal or excess zinc, there was a marked decrease in plasma zinc from the 24-hr fasting value when the supplement contained either soybean or egg white protein. When zinc was added to the supplement, the effect of protein on plasma zinc level was unchanged. Supplements of glucose or corn oil plus cellulose did not result in the marked lowering of plasma zinc that was observed with protein. Plasma zinc was significantly increased when zinc was added to the supplement of glucose or corn oil plus cellulose.

Under conditions of rapid protein metabolism, it appears that one might expect a significant decrease in the plasma zinc level.

The authors wish to thank Jesse J. Gantt, Geneva Clark, Francenia V. Grinnage, and Maggie Smith, Food and Drug Administration, for excellent technical assistance and care of the birds; and F. E. Calvert, Ralston Purina Co., who supplied lots of soybean protein selected for their low zinc content.