University of Guilan Aquatic Physiology and Biotechnology 2345-3966 7 4 2020 03 09 Dietary choline requirement of juvenile narrow-clawed crayfish (Astacus leptodactylus) in a recirculating aquaculture system Dietary choline requirement of juvenile narrow-clawed crayfish (Astacus leptodactylus) in a recirculating aquaculture system 41 62 3946 10.22124/japb.2020.12163.1299 FA Reza Jalili Ph.D. Student of Fisheries Sciences, Department of Fisheries, Faculty of Natural Resources, Urmia University, Urmia, Iran Naser Agh Associate Professor in Artemia and Aquaculture Research Institute, Urmia University, Urmia, Iran Ahmad Imani Associate Professor in Department of Fisheries, Faculty of Natural Resources, Urmia University, Urmia, Iran Farzaneh Noori Assistant Professor in Artemia and Aquaculture Research Institute, Urmia University, Urmia, Iran Journal Article 2018 12 23 It has been shown a dietary choline is essential for several crustacean species. However, the choline requirement of narrow-clawed crayfish has not been reported. Therefore, a 12-week feeding trial was conducted to determine the dietary choline requirement of narrow-clawed crayfish. Juvenile crayfish with an average body weight of 13.8±0.9g were intensively stocked in an indoor recirculating aquaculture system consisting of 12 tanks. Four experimental diets were formulated to contain graded levels of dietary choline (0, 0.2, 0.4 and 0.8% choline chloride). Results showed a crayfish fed diet with 0.0 and 0.2 % choline produced the highest and the lowest growth indices and enzymes activity including protease and amylase, respectively (P<0.05). With an increase of choline content of experimental diets (0.4 and 0.8 %), no significant improvement was observed regarding growth indices, protease, and amylase activity (P>0.05). However, no significant differences were observed in survival rate and lipase activity of various experimental groups (P>0.05). In conclusion, the results indicated that dietary inclusion of 0.2% choline would improve growth performance and digestive enzymes activity of juvenile narrow-clawed crayfish reared under intensive condition. It has been shown a dietary choline is essential for several crustacean species. However, the choline requirement of narrow-clawed crayfish has not been reported. Therefore, a 12-week feeding trial was conducted to determine the dietary choline requirement of narrow-clawed crayfish. Juvenile crayfish with an average body weight of 13.8±0.9g were intensively stocked in an indoor recirculating aquaculture system consisting of 12 tanks. Four experimental diets were formulated to contain graded levels of dietary choline (0, 0.2, 0.4 and 0.8% choline chloride). Results showed a crayfish fed diet with 0.0 and 0.2 % choline produced the highest and the lowest growth indices and enzymes activity including protease and amylase, respectively (P<0.05). With an increase of choline content of experimental diets (0.4 and 0.8 %), no significant improvement was observed regarding growth indices, protease, and amylase activity (P>0.05). However, no significant differences were observed in survival rate and lipase activity of various experimental groups (P>0.05). In conclusion, the results indicated that dietary inclusion of 0.2% choline would improve growth performance and digestive enzymes activity of juvenile narrow-clawed crayfish reared under intensive condition. https://japb.guilan.ac.ir/article_3946_1f0f4f699155be73e6dcb966786a4349.pdf