Effects of vitamin A inclusion in practical diets on survival and growth of juvenile crayfish ( P acifastacus 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 A on survival and growth of juvenile crayfish ( P acifastacus leniusculus ). An 80‐day trial was conducted with stage 2 juveniles from the onset of exogenous feeding. Four diets differing in the level of retinyl acetate were tested: 0, 0.0025, 0.0050 or 0.0100 g kg −1 diet, equivalent to 0, 2500, 5000 or 10 000 IU vitamin A kg −1 diet, respectively. Each diet was tested on grouped or individually isolated crayfish. Crayfish fed the diet with 5000 or 10 000 IU vitamin A kg −1 diet achieved the highest survival (average of grouped and isolated: 88.9%) and growth (grouped and isolated: 13.45 mm carapace length, 533.4 mg weight). Final growth of isolated crayfish was significantly higher than that of grouped crayfish for all diets. This study provides the first data on vitamin A requirements of freshwater crayfish. A level of 5000 IU vitamin A kg −1 can be recommended for juvenile P. leniusculus during the first period of intensive rearing.