REQUIREMENT AND UTILIZATION OF ASCORBIC-ACID AND ASCORBIC SULFATE IN JUVENILE RAINBOW-TROUT

Ascorbate status was analyzed in fish offered a diet deficient in ascorbate or diets supplemented with graded levels of ascorbic acid or ascorbic sulfate. Alizarin red staining of vertebrae detected an apparent de-calcification process in fish devoid of dietary ascorbate. Distorted and twisted filamental cartilage and distension of eye scleral cartilage were observed long before acute damage of the spinal column. By the end of a 176-day experiment, significant differences in growth were exhibited between groups fed an ascorbate-deficient diet and a 500 mg ascorbic acid (AA)/kg supplemented diet. Total ascorbate concentration in fish viscera (gut and liver) increased during the experiment in fish fed a diet supplemented with 500 mg AA/kg, whereas it decreased in other groups. Total ascorbate concentration in viscera of fish that were fed a diet supplemented with 500 mg ascorbic sulfate (AS)/kg was six-fold lower than in fish fed an equivalent AA diet. The requirement based on the minimal supplemental ascorbic acid level that produced no external deficiency signs in this study (20.4 mg AA/kg) markedly differed from the dietary level ensuring the maintenance of body ascorbate concentration (264 mg AA/kg). There was a noticeable decrease in body Ca in fish fed an ascorbate-free diet for 84 days compared to fish supplemented with AS or AA. A significant decrease in body Cu and Zn was found after 176 days in fish fed a diet supplemented with 500 mg AA/kg compared with other groups. © 1990.