Substitution effect of fish meal with various animal and/or plant protein sources, and their combination in the feeds of juvenile rockfish (Sebastes schlegeli) on growth performance

Abstract

This study investigated the substitution effect of the fish meal (FM) with various animal and plant protein sources and their blends in the diet on growth, feed utilization, biological indices, chemical composition, plasma chemistry, and non-specific immune response of juvenile rockfish (Sebastes schlegeli). A total of 1,080 juvenile (initial weight of 2.4 g) rockfish was randomly distributed into 27, 250-L flow-through tanks (3 tanks per diet; 40 fish/tank). All experimental fish were hand-fed twice a day for 8 weeks. Nine experimental diets were prepared. The control diet (Con) contained 60% FM. In the Con diet, FM level was reduced by 35%, and a reduced amount of FM (25% in diet) was substituted with equal amount of protein from tuna by-product meal (TBM), duck by-product meal (DBM), corn gluten meal (CGM), and microalgal meal (Schizochytrium sp., SCH), and their 1:1 blends (TBM and CGM, TBM and SCH, DBM and CGM, and DBM and SCH) (referred to as the TBM, DBM, CGM, SCH, CTC, CTS, CDC, and CDS diets respectively). After 8 weeks feeding trial, weight gain and specific growth rate (SGR) of rockfish fed the DBM, SCH, CTS, and CDS diets were not significantly (P > 0.05) different from those of fish fed the Con diet. The highest feed consumption of fish was observed in fish fed the CTS diet, followed by the CDS, SCH, Con, DBM, TBM, CDC, CTC, and CGM diets, in that order. Feed efficiency (FE) and protein efficiency ratio (PER) of rockfish fed the TBM, DBM, SCH, CTS, and CDS diets were not significantly (P > 0.05) different from those of fish fed the Con diet. Protein retention (PR), biological indices, hematological parameters, non-specific immune response, chemical composition, and amino acid profiles of the whole body of fish were not significantly influenced by the experimental diets (P > 0.05 for all). In conclusion, when rockfish diets contain 60% FM, DBM, SCH, CTS, and CDS can be successfully included by reducing the FM level by 35% without retardation on growth performance, feed consumption, feed utilization, biological indices, hematological parameters, non-specific immune responses, and AA profiles of the whole body of rockfish.