Effect of different dietary protein levels on growth of juvenile Caspian trout (Salmo trutta caspius)

The effects of dietary protein levels on growth and feed efficiency were investigated in Caspian trout, Salmo trutta caspius. Five experimental diets containing five different dietary levels of protein (35, 40, 45, 50 and 55% diet) were fed to triplicate groups of 225 with an initial weight of 4.85 ± 0.45 g for 63 days. Oxygen concentration was 7.6 ± 0.68 mg L-1 and average water temperature was 17.7 ± 1.5 °C was in effect throughout the experimental period. Significant higher Final body weight, weight gain, specific growth rate, protein efficiency ratio and condition factor were observed in fish fed diet supplemented with optimum levels of protein (40 and 45%) than that of fish of other dietary groups such as 35 and 55 % protein. Feed efficiency ratio of fish fed 35 and 55 % protein were significantly higher than those of fish fed 40 and 45% dietary protein levels (P≤ 0.05).  There were no significant differences in white blood cell content of serum in all treatments, expect fish fed diet containing 45 % protein that was significantly higher than that of fish fed other diets. Lysozyme activity of fish fed 55 % protein was significantly higher than this of fish fed 35 % protein.  Based on the results of this study, could say that increased levels of protein in the diets of juvenile Caspian trout (Salmo trutta caspius) up to 40- 45% in diet, improved growth performance, feed utilization parameters and nonspecific immune response.