Evaluation of four commercial feed additives and three isolated probiotics to replace antibiotics in juvenile olive flounder Paralichthys olivaceus fed the low fishmeal diet

Abstract

Three experiments were conducted to evaluate four commercial feed additives and three recently isolated probiotics to replace antibiotics in juvenile olive flounder Paralichthys olivaceus. In the first experiment, a basal diet without feed additives was used as a control (CON); the other diets were formulated by adding 0.5% taurine (TW), 0.3% peptide (PT), 0.217% mineral water (MW), 0.35% Gropro (GRO), 0.35% Gropro + 0.5% taurine (GROTW), 0.35% Gropro + 0.3% peptide (GROPT), or 0.35% Gropro + 0.217% mineral water (GROMW) to the basal diet. Based on growth performance, non-specific immune responses, disease resistance, gene expression and intestinal histology GRO, GROMW, GROPT and GROTW could be beneficial feed additives to replace antibiotics in the low-fishmeal diet for juvenile olive flounder. In the second experiment, a basal diet without feed additives was used as a control (CON); the other diets were formulated by adding 1×108 CFU/g Bacillus subtilis WB60 (BSWB60), 1×108 CFU/g B. subtilis SJ10 (BSSJ10), 1×107 CFU/g Entarococuus faecium SH30 (EFSH30), 4g/kg amoxicillin (AMO) or 4g/kg oxytetracycline (OTC) to the basal diet. Based on growth performance, non-specific immune responses, disease resistance, gene expression and intestinal histology B. subtilis at 108 CFU/g and E. faecium at 107 CFU/g diets could be beneficial feed additives to replace antibiotics in the low-fishmeal diet for juvenile olive flounder. In the third experiment, a basal diet without feed additives was used as a control (CON); the other diets were formulated by supplementing 1×108 CFU/g Bacillus subtilis WB60 (BSWB60), 1×108 CFU/g Bacillus subtilis SJ10 (BSSJ10), 1×107 CFU/g Entarococuus faecium SH30 (EFSH30), 4 g/kg amoxicillin (AMO), 4 g/kg oxytetracycline (OTC) or 0.35% Gro-pro (GRO) to the control diet. Results showed that dietary supplementation of Gropro at 0.35%, B. subtilis WB60 at 108 CFU/g, B. subtilis SJ10 at 108 CFU/g and E. fassium at 107 CFU/g could improve growth performance, immune responses, gene expression and intestinal condition. Therefore, these results could indicate that dietary nucleic acid (GRO-PROTM) has effects and three recently isolated probiotics (Japanese eel BSWB60, Jeotgal BSSJ10, Tilapia EFSH30) has beneficial effects on growth, immune responses, histology, disease resistance and gene expression to replace antibiotics for the low fishmeal diet in juvenile olive flounder, Paralichthys olivaceus.