Evaluation of tuna by-product meal as a protein source in feeds for juvenile spotted rose snapper Lutjanus guttatus

Abstract

This study evaluated the use of tuna by-product meal (TBM), a locally produced feed ingredient, as a replacement for fish meal (FM) in diets for spotted rose snapper, Lutjanus guttatus. Six isonitrogenous compounds [480 kg-1 crude protein (CP) and isoenergetic diets (21 kJ g-1)] were formulated to replace 0 (D-0%), 10 (D-10%), 20 (D-20%), 30 (D-30%), 40 (D-40% or 50% (D-50%) of FM protein with TBM protein. Each diet was fed to four replicate groups of spotted rose snapper (initial weight 5.4 g ± 0.04 g) to apparent satiation three times a day. After 8 weeks of feeding, the fish gained 4-5 times their initial weight. Spotted rose snapper fed D-30% had a significantly higher specific growth rate (2.7% day-1) than fish fed the other diets containing lower or higher amounts of TBM. Haematological parameters and whole-body proximate composition were unaffected by diet (P > 0.05). The ADC for protein and energy in D-0%, D-20% and D-30% were significantly higher than those for the D-40% and D-50% groups. A broken line model indicated that 262 g kg-1 TBM in the diet would yield maximum growth of the spotted rose snapper. The results of this study demonstrate that TBM is an acceptable ingredient for replacing 25-30% of dietary protein from FM in spotted rose snapper diets but that higher replacement levels reduce fish performance.