Evaluation of growth performance and whole-body composition of juvenile hybrid striped bass Morone chrysops x Morone saxatilis and red drum Sciaenops ocellatus fed high-protein and high-lipid diets

To investigate potential use of increasing nutritional density of diets for rapid growth of warm-water fishes, a feeding trial was conducted in which growth performance, body indexes, and whole-body composition of juvenile hybrid striped bass fed diets comprising protein (49, 54, and 59%), lipid (16, 20, 23, and 28%), and energy (22.0-25.1 kJ/g) concentrations beyond established minimum levels were compared to those of fish fed a more typical commercial reference diet (37.5% crude protein, 10.5% crude lipid, and 19.6 kJ/g energy on a dry matter basis). A subset of the experimental diets and the commercial reference diet also were fed to juvenile red drum. After 6 wk of feeding, hybrid striped bass fed the high-protein and high-lipid diets showed much greater growth performance compared to fish fed the commercial diet. Increasing dietary protein level, but not lipid level, tended (P <= 0.1) to enhance weight gain and feed efficiency of hybrid striped bass. Hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and whole-body protein were significantly (P < 0.01) influenced by dietary protein level. The dietary lipid and associated energy level had significant negative linear effects on daily feed intake. Linear regression analysis showed that dietary energy : protein ratio, largely influenced by dietary protein level, moderately but significantly influenced weight gain, HSI, IPF ratio, and whole-body protein of hybrid striped bass and red drum. Red drum grew very similar to hybrid striped bass in response to the experimental diets. However, significant differences in HSI, IPF ratio, whole-body protein, lipid, moisture, and ash between hybrid striped bass and red drum were observed, indicating species differences in protein and energy partitioning. In particular, the excessive lipid in the diet increased HSI and whole-body lipid of red drum but not of hybrid striped bass.