Quantitative dietary lysine requirement of juvenile striped bass Morone saxatilis

Two feeding trials of 8 and 10 weeks each were conducted to quantify the dietary lysine requirement of juvenile striped bass, Morone saxatilis. Diets in both experiments contained approximately 420 g crude protein kg(-1) and 13.4 MJ digestible energy (DE) kg(-1). L-Lysine-HCl was added to the basal diet to yield five and six treatments in the two experiments. Diets in the first experiment were determined to contain 9.2, 14.1, 14.6, 19.9 and 21.0 g available lysine kg(-1) on a dry-matter basis. Diets in the second experiment were determined to contain 14.8, 18.1, 21.3, 24.5, 27.6 and 30.9 g available lysine kg(-1) on a dry-matter basis. Weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and apparent nitrogen utilization (ANU) were significantly (P < 0.05) improved by increasing dietary lysine concentrations to approximately 20 g kg(-1) of diet. Least-squares regression analysis of weight gain and SGR in the first experiment indicated a minimum dietary lysine requirement of 20.1 +/- 2 g kg(-1) dry diet. Least-squares regression analysis of the same criteria measured in the second experiment yielded the following estimates of dietary lysine requirements (g kg(-1) dry diet): 19.8 +/- 2.3 for weight gain, 21.7 +/- 1.5 for SGR, 23.7 +/- 3.5 for FCR and 18.6 +/- 1.3 for ANU. From these results the minimum recommended dietary lysine requirement for optimal growth of juvenile striped bass is approximately 21 g kg(-1) dry diet which equates to 49 g kg(-1) dietary protein or 1.57 mg kJ(-1) DE. Although higher than that reported for hybrid striped bass, this requirement level is similar to those reported for many other fish species.