Evaluation of Poultry By-Product Meal as an Alternative to Fish Meal in the Diet of Juvenile Black Sea Bass Reared in a Recirculating Aquaculture System

A feeding trial was conducted to determine the maximum substitution limits of poultry by-product meal (PBM; 66% crude protein) protein for fish meal (FM; 59% crude protein) protein in the diet of juvenile Black Sea Bass Centropristis striata (family Serranidae). Eight isonitrogenous (44% crude protein) and isolipidic (13% crude lipid) diets were formulated to replace FM protein with PBM protein at 0 (control), 40%, 50%, 60%, 70%, 80%, 90%, and 100% in Black Sea Bass diets. Diets were fed twice daily to triplicate groups of juveniles (initial mean weight = 1.2 g) to apparent satiation for 8 weeks in a recirculating aquaculture system. Final survival was excellent (95-100%) in all diet treatments, with no significant differences. No significant differences in body weight gain (BWG) were observed in fish fed the 40-90% PBM protein diets (1,136-1,357%) compared with the control diet (1,307%). However, BWG of fish fed the 100% PBM protein diet (1,045%) was significantly lower than in the control group. Regression analysis with BWG indicated that PBM protein can replace FM protein in Black Sea Bass diets at levels as high as 81.8%, with no reduction in fish growth performance. For fish fed diets with up to 90% PBM protein, feed conversion (1.08-1.17) and protein efficiency ratios (2.01-2.14) were not significantly different from fish fed a control 100% FM-protein-based diet (0.99 and 2.29, respectively). Apparent digestibility coefficients of dietary protein remained high (81.6-87.0%) under all levels of FM replacement with PBM protein. After the feeding trial, whole body and muscle protein content and the concentrations of whole body n-3 polyunsaturated fatty acids showed no significant differences among the treatments at FM protein replacement levels up to 90%. Poultry by-product meal is a promising alternative protein source for sustainable diet development in Black Sea Bass.