Predicting dietary essential amino acid requirements for hybrid striped bass

Abstract

Three experiments were conducted that were designed to evaluate our ability to predict essential amino acid (EAA) needs of hybrid striped bass using the quantified lysine requirement and whole-body amino acid concentrations. In the first experiment, six diets containing various amino acid profiles were fed to triplicate groups of fish initially weighing 7.7 g per fish. At the end of the 8-week experiment, no significant differences were detected in growth rates or feed efficiencies (FE) between fish fed a practical diet containing 510 g kg−1 herring fish meal (FM) and fish fed a purified diet containing the amino acid profile of herring fish meal (CAA-FM). Growth responses of fish fed purified diets containing 100 (HSB), 110 (HSB110), 120 (HSB120) or 140 g 100 g−1 (HSB140) of the amino acid profile of hybrid striped bass whole-bodies were significantly lower than those of fish fed diet FM. In the second experiment, triplicate groups of fish (5.6 g per fish) were fed diets containing various energy : protein (E : P) ratios (34.8, 41.2, 47.5 and 53.9 kJ g−1 protein) and one of two amino acid profiles (CAA-FM and HSB120) in a 4 × 2 factorial design. Carbohydrate concentration was varied to achieve the desired energy concentrations. At the end of the 8-week experiment, weight gain and FE were significantly higher in fish fed diets formulated to simulate the amino acid profile of herring fish meal (CAA-FM) compared with fish fed diets formulated to contain 120 g 100 g−1 of the amino acid profile of hybrid striped bass whole-bodies (HSB120). Weight gain, FE and survival data indicated the optimum dietary E : P was 41.2 kJ g−1 protein. Dietary treatments in the final experiment included three amino acid profiles and four levels of lipid in a 3 × 4 incomplete factorial design. Dietary amino acid treatments included the amino acid profile of herring fish meal (CAA-FM) or 120 g 100 g−1 of the predicted EAA requirement profile for hybrid striped bass (HSB120). The amino acid profile of the remaining dietary treatment (PRED+) was similar to that of the HSB120 treatment, but contained additional threonine, isoleucine and tryptophan. Diets CAA-FM and HSB120 contained either 90, 130, 170 or 210 g kg−1 lipid, whereas diet PRED+ contained 130 g kg−1 lipid. Dietary treatments were fed for 10 weeks to triplicate groups of fish initially weighing 81.0 g per fish. Weight gain and FE were not significantly affected by dietary amino acid profile. Feed efficiency was significantly reduced in fish fed diets containing 210 g kg−1 lipid compared with fish fed diets containing 90–170 g kg−1 lipid. Intraperitoneal fat (IPF) ratio and hepatosomatic index (HSI) values generally increased as dietary lipid concentrations increased. Total liver lipid concentrations were significantly reduced in fish fed diets containing 210 g kg−1 lipid compared with those of fish fed 90–130 g kg−1 lipid. Results of this study indicate an appropriate dietary amino acid profile can be predicted for hybrid striped bass using the quantified lysine requirement and whole-body amino acid concentrations. Further, the optimum E : P appears to be 40 kJ g−1 protein.