Optimal dietary lipid requirement for juvenile Asian red-tailed catfish (Hemibagrus wyckioides)

This study investigated the effects of dietary lipid content on growth rate, feed utilization, digestive enzyme activity, and antioxidant capacity of juvenile Asian red-tailed catfish (Hemibagrus wyckioides), and thereby to evaluate the optimal dietary lipid requirement. Five isoproteic diets were prepared to contain varied levels of dietary lipid (3 %, 5.5 %, 8 %, 10.5 %, and 13 %). Each diet was fed to triplicate groups of juveniles (average body weight 3.20 g) in a recirculating farming system maintained at 28 ± 1 °C. Daily gain coefficient (DGC) and protein efficiency ratio improved steadily with the dietary lipid content up to 10.5 %, and then reached a plateau. Similarly, protein retention increased gradually with the dietary lipid content up to 13 %. Conversely, lipid retention decreased linearly with increasing dietary lipid content, but no significant difference was found among juveniles fed diets with 8 %, 10.5 %, and 13 % lipid. The optimum feed conversion ratio (FCR) was observed in juveniles fed diets with 10.5 % or 13 % lipid. Plasma insulin-like growth factor 1 level increased steadily with the dietary lipid content up to 8 %. However, plasma amino methyl propanediol, aspartate aminotransferase and alanine aminotransferase activities depressed generally with increasing dietary lipid content. Besides, the highest hepatic peroxidase, catalase, glutathione peroxidase, and alkaline phosphatase activities were found in juveniles fed diet with 10.5 % lipid. Single-slope broken-line regression analysis of DGC or FCR response to varied levels of dietary lipid showed that the optimal dietary lipid requirement of juvenile H. wyckioides was 11.1 % or 9.4 % of diet containing 42 % protein, respectively.