Effects of vitamin C inclusion in practical diets on survival and growth of juvenile crayfish (Pacifastacus leniusculus Dana, Astacidae) from the onset of exogenous feeding

The aim of this study was to evaluate the effects of practical diets with different levels of vitamin C on survival and growth of juvenile crayfish (Pacifastacus leniusculus). An 80-day trial was conducted with stage 2 juveniles from the onset of exogenous feeding. Four practical diets differing in the content of l-ascorbyl-2-monophosphate-Na were prepared: 0, 0.2, 0.4 or 0.8 g kg-1 diet. Each diet was tested on grouped or individually isolated crayfish. Diets had no significant effects on survival of crayfish held in groups (average: 73.1%) neither on the isolated ones (average: 90%). Crayfish fed the diet with 0.2 g kg-1 of l-ascorbyl-2-monophosphate-Na had the highest growth (groups: 13.64 mm carapace length (CL), 542.4 mg weight; isolated: 17.05 mm CL, 1213.2 mg weight) and the lowest feed conversion ratio (average of grouped and isolated: 0.99). This study provides the first data on vitamin C requirements of freshwater crayfish. A level of 0.2 g l-ascorbyl-2-monophosphate-Na kg-1 diet (0.07 g ascorbic acid equivalent) can be recommended for juvenile P. leniusculus during the first period of intensive rearing.