DIETARY ARGININE REQUIREMENT OF JUVENILE HYBRID STRIPED BASS

Two experiments were conducted to determine the dietary arginine requi rement of juvenile hybrid striped bass (Morone saxatilis x M. chrysops ); a third experiment evaluated the interaction of lysine and arginine . Diets in Experiments 1 and 2 were supplemented with graded concentra tions of L-arginine-HCl, resulting in eight dietary treatments. Dietar y arginine concentrations ranged from 1.0 to 2.4 g/100 g diet in Exper iment 1 and from 0.6 to 2.0 g/100 g diet in Experiment 2. Weight gain was not affected by dietary treatments in Experiment 1. Feed efficienc y was significantly affected by dietary arginine concentrations, and t he data, when subjected to broken-line analysis, resulted in a require ment estimate of 1.53 +/- 0.20 g/100 g diet. Weight gain and feed effi ciency were both significantly affected by dietary arginine concentrat ions in Experiment 2. Broken-line analyses of weight gain and feed eff iciency data indicated the dietary arginine requirement to be 1.55 +/- 0.10 and 1.45 +/- 0.12 g/100 g diet, respectively. Diets in Experimen t 3 contained lysine and arginine in ratios of 1:1, 1:1.5, 1:2 and 1:2 .5 for the previously estimated requirements for both lysine:arginine and arginine:lysine. No differences were observed in weight gain or fe ed efficiency for fish fed various lysine:arginine ratios, but serum l ysine was significantly different among treatment groups.