Assessment of rapeseed meal as fish meal alternative in diets for juvenile Asian red-tailed catfish (Hemibagrus wyckioides)

This study investigated the effects of rapeseed meal (RM) as fish meal (FM) alternative on the growth rate, feed utilization, protein metabolism-related parameters, and antioxidant indices of Asian red-tailed catfish (Hemibagrus wyckioides). Five isoproteic and isocaloric diets were formulated with 0%, 11.2 %, 22.4 %, 33.6 %, and 44.8 % RM replacing graded levels of FM, respectively. Each experimental diet was randomly offered to juvenile catfish (initial average weight 3.24 g) in triplicate tanks for 8 weeks. The substitution of FM by RM linearly depressed the growth rate and feed utilization of fish, whereas no significant influences were observed among fish fed diets containing 0%, 11.2 %, and 22.4 % RM. Similarly, the substitution of FM by RM also linearly reduced the gastrointestinal digestive enzymes (pepsin, trypsin, lipase, and amylase) activities, but raised the plasma aspartate aminotransferase and hepatic gamma-glutamyl transferase activities. The relative repression levels of mammalian target of rapamycin and insulin-like growth factor 1 in liver, adenosine monophosphate deaminase 1 and glutamate dehydrogenase genes in liver and muscle were higher in fish fed diets with 0% and 11.2 % RM compared with those fed the other diets. Further, dietary 11.2 % RM inclusion did not negatively affect the plasma IgM and malondialdehyde contents, and hepatic superoxide dismutase, catalase, peroxidase, and glutathione peroxidase activities. These results indicate that a maximum of 11.2 % RM in diets can be included without negative impacts on the growth and health of H. wyckioides; the detrimental effect of higher inclusion levels of RM may be attributed to the existence of antinutritional factors (mainly glucosinolates) present in RM.