Evaluation of Bacillus sp. SW1-1 as a dietary additive in diets for olive flounder Paralichthys olivaceus

Abstract

Listen

Translate article

This study was conducted to investigate the impact of dietary Bacillus sp. SW1–1 (SW) on innate immunity, disease resistance, growth performance, feed utilization and diet digestibility of juvenile olive flounder ( Paralichthys olivaceus ). A fish meal-based diet was considered as a control and five other experimental diets were prepared to contain SW at levels of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% (designated as SW-0.1, SW-0.2, SW-0.3, SW-0.4 and SW-0.5). Triplicate groups of fish (initial body weight 9.26 ± 0.06 g) were fed one of the experimental diets to apparent satiation twice daily for 14 weeks. After the feeding trial, growth rate was increased showing significant linear trend with increase of SW level in diets. Significantly higher survival was observed in fish fed SW-0.2, SW-0.4 and SW-0.5 compared to the control group. Lysozyme activity of fish fed SW-0.4 was significantly higher than that of fish fed the control diet. Anti-protease activity was significantly higher in SW-0.4 group compared to control. Superoxide dismutase activity of fish fed SW-0.2 diet was significantly higher than that of fish fed control diet. Glutathione peroxidase activity was significantly increased by the dietary supplementation of SW. Digestibility of protein and dry matter was significantly higher in SW-0.2, SW-0.3, SW-0.4 and SW-0.5 groups than that of control group. Plasma alanine aminotransferase level was reduced with the increase of SW in diets. Challenge test against Streptococcus iniae showed that fish fed SW-0.4 diet had significantly higher survival compared to fish fed the control diet. Therefore, this study indicates that dietary supplementation of SW can enhance activity of antioxidant enzymes, innate immunity, digestibility and disease resistance of olive flounder. • Supplemental effect of Bacillus sp. SW1-1 as dietary additives was tested in diets for olive flounder. • Innate immunity, antioxidant status, diet digestibility and feed utilization of olive flounder were enhanced by SW1-1. • Dietary SW1-1 supplementation improved the disease resistance of olive flounder against Streptococcus iniae .