Dietary Chlosterol Requirement of Juvenile Narrow-clawed Crayfish (Astacus leptodactylus) in a Recirculating Aquaculture System

Dietary cholesterol has been shown to be essential for several crustacean species. However, cholesterol requirement of narrow-clawed crayfish has not been reported. Therefore, a 12-week feeding trial was conducted to determine deitary cholesterol requirement of narrow-clawed crayfish. Juvenile crayfish with an average body weight of 13.8±1 g mean weight were intensively stocked in an indoor recirculating aquaculture system consisting of 12 rectangular fiberglass tanks with 10% daily water exchange under constant aeration and PVC shelters. Water was recirculated through biological and mechanical filters. Four experimental diets with 30% crude protein and 10% crude lipid were formulated to contain graded levels of dietary cholesterol (0, 0.25, 0.5 and 0.75 % Cholesterol). Casein and gelatin were used as primary sources of dietary protein in experimental diets. Our results showed crayfish fed diet with 0.5 and 0.0 % cholesterol level produced the highest and lowest growth indices, survival rate and enzymes activity including protease, lipase and amylase, respectively significant (P<0.05). With increase of cholesterol content of experimental diet (0.75 %) crayfish survival rate and lipase activity siginificantly decreased, however, no significant differences were observed regarding growth indices, protease and amylase activity (P>0.05). In conclusion, the results indicated that dietary inclusion of 0.5% cholesterol would improve growth performance and digestive enzymes activity of juvenile narrow-clawe crayfish reared under intensive condition.