Inclusion of a commercial poultry by-product meal as a protein replacement of fish meal in practical diets for African catfish Clarias gariepinus (Burchell 1822)

This study examined the full and partial replacement of the fish meal component of practical diets with commercial poultry by-product meal (PBM) for juvenile African catfish Clarias gariepinus (Burchell 1822). Six test diet formulations were based on a low temperature Norwegian fish meal (LT94) as the reference protein source. Dietary inclusion levels of PBM at 20%. 40%, 60%, 80% and 100% substitution of total protein content were compared with the fish meal-based control diet (100% fish meal). All diets were iso-nitrogenous and isocaloric in gross terms. The results showed that there were significant differences (P < 0.05) between the final average weights of fish at the end of a 10-week feeding trial. Growth performance, feed intake, feed conversion ratio, protein efficiency ratio and specific growth rate were all depressed for catfish fed the highest levels of PBM diets compared with the fish meal group. It was inferred that amino acid profile and digestibility of protein were mainly responsible for these effects, together with reduced palatability. PBM may successfully replace up to 40% of the protein component in practical feeds for this species. Histological examination of liver tissue showed alterations in hepatic structure of those fish fed diets with higher levels of PBM. © 2001 Blackwell Science Ltd.