Zinc Requirement and Balance Studies with the Rat

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Abstract
In a series of growth and balance studies concerned with investigating factors affecting the zinc requirement of the young albino rat, increasing calcium level from 0.8 to 1.6% of the diet was observed to depress weight gain at all levels of zinc fed both in diets containing casein and those containing isolated soybean protein. Apparent absorption of dietary zinc and its urinary excretion were not affected by increased calcium. Zinc requirement was 18 ppm with 7 ppm derived from soy protein and the remainder from ZnCO3; 12 ppm with 7 ppm supplied from casein and 5 from ZnCO3; and 12 ppm with 2 to 4 ppm derived from egg white and the remainder from ZnCO3. Apparent absorption of zinc from casein, ZnCO3 and isolated soybean protein was 84, 51 and 44%, respectively.