Riboflavin Requirement of Fingerling Rainbow Trout

Fingerling rainbow trout (Salmo gairdneri) were fed purified diets containing graded levels (0, 3, 6, 12, 18, 24, and 54 mg/kg) of supplemental riboflavin for 20 weeks. The cellular riboflavin supply of the fingerlings was estimated on the basis of the activity of the FAD-dependent enzyme, erythrocyte glutathione reductase (EGR). The dietary riboflavin level that produced the fastest growth, an efficient feed: gain ratio, and normal values for the EGR activity coefficient was about 3 mg of supplemental riboflavin per kilogram of diet.