Dietary riboflavin requirement of juvenile sunshine bass (Morone chrysops ♀ x Morone saxatilis ♂)

An 8-week growth trial was carried out to estimate the dietary riboflavin requirement of juvenile sunshine bass. Seven purified diets (350 g'protein and 3480 kcal available energy/kg dry diet) were formulated to contain: 1.37, 3.45, 4.72, 6.60, 8.43, 9.97 and 12.32 mg riboflavin/kg dry diet. Each diet was randomly assigned to three groups of fish. Fish were maintained in flow-through aquaria (1101/tank) at a water temperature of 25 +/- 0.5 degreesC with 20 fish each (1.94 +/- 0.02 g, mean +/- SEM n=20). Fish were fed twice per day to apparent satiation. Fish fed the diet containing 1.37 mg riboflavin/kg dry diet showed significantly higher mortality, lower weight gain, lower feed efficiency and lower hepatic D-amino acid oxidase activity (D-AAO) compared with fish fed the other diets. Riboflavin-deficient fish exhibited anorexia, dark body color and cataracts. A dietary level of 3.45 mg riboflavin/kg dry diet was sufficient to prevent the deficiency signs. A higher level of dietary riboflavin, however, was required to obtain maximum weight gain and D-AAO activity. Based on broken-line analysis, the dietary riboflavin requirements were 4.1 and 5.0 mg/kg dry diet based on maximum weight gain and D-AAO activity, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.