Vitamin D-deficient rainbow trout at 150–200 g body weight
were fed the semi-purified diet which had been fortified with
612 mg cholecalciferol per kg dry ingredients. Four trout were then
sacrificed at weekly intervals and the concentrations of calcium
and 1,25(OH)2D3 in blood plasma were measured. After 1 week on
the vitamin D-fortified diet the
fish had become hypercalcemic but
blood calcium returned to the normal range after 2 weeks (Fig. 4).
The concentration of 1,25(OH)2D3 in plasma rose gradually to a
maximum of about 180 pg/ml after about 4 weeks and thereafter
declined to a range of 60–80 pg/ml (Fig. 5).