Effects of dietary protein and different levels of replacement of fish meal by soybean meal in practical diets for juvenile crayfish (Pacifastacus leniusculus, Astacidae) from the onset of exogenous feeding

Two 100-day experiments were conducted to evaluate effects of practical diets with different protein content and substitution possibilities of fish meal (FM) protein with soybean meal (SBM) protein on survival and growth of juvenile crayfish (Pacifastacus leniusculus) from the onset of exogenous feeding. In experiment 1, four practical diets were prepared to contain 35, 40, 45 or 50% crude protein. Each diet was fed to crayfish housed individually or as a group. Survival rates of isolated crayfish fed 45 or 50% dietary protein were the highest (100%). There were no significant effects on survival of grouped crayfish (average: 75.09%). Weight gain plateaued at 45% crude protein (grouped and isolated crayfish: 14.56 mm CL, 691 mg W). Final growth values of isolated crayfish were significantly higher than those of grouped crayfish for all protein levels tested. In experiment 2, four practical diets (50% crude protein content) were prepared to test replacement levels of FM protein by SBM protein of 0% (control group), 25%, 35% or 45%, in crayfish housed in groups. Replacement levels of 0% and 25% SBM enabled the highest survival (average: 74%) and growth (average: 14.49 mm CL, 651.9 mg W). The amino acids profile of all diets is presented and compared with the requirements determined for other crustacean species. In conclusion, a 45–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile P. leniusculus during the first period of intensive rearing.

► Two experiments were conducted with juvenile crayfish (Pacifastacus leniusculus).
► We tested different dietary protein contents from the onset of exogenous feeding.
► Levels of soybean meal (SBM) were evaluated at the beginning of intensive rearing.
► Levels of protein and SBM were related to the amino acid content of diet and growth.