Prebiotics and probiotics are well known as functional feed additives that can improve growth, immunity and disease resistance enhancing balance of intestinal microbiome. For that reason, dietary utilization of prebiotics and probiotics in various fish species are being studies. Therefore, this study was performed to evaluate the effects of dietary supplementation of mannan oligosaccharides, Lactobacillus plantarum, Bacillus subtilis and Bacillus licheniformis on innate immunity and disease resistance of feeding trial and bacterial infection test of growing olive flounder.
A basal diet (Con) was formulated to meet the nutrient requirements of olive flounder. Dietary starch in Con was replaced with 0.6% of manna oligosaccharides, L. plantarum, B. subtilis, B. licheniformis (Mos, LP, BS and BL, respectively ) and each 0.15% of prebiotic and probiotics (Syn). Total 450 fish (i nitial body weight: 65.9 g) were stocked in 18 tanks (240 L), divided into three replicates for each dietary treatment. Fish were fed ad libitum one of the diets twice a day (08:00, 17:30 h) for 11 weeks. After the feeding trial, bacterial infection test against Edwardsiella tarda was performed for 17 days.
After the feeding trial, activity of phagocytic and myeloperoxidase was not affected by the supplementation (Table 1). Lysozyme activity of LP, BL and Syn groups, and immunoglobulin level of MOS, LP, BL and Syn groups were significantly higher t han that of Con group. After the bacterial infection, lysozyme activity and immunoglobulin level were also significantly increased in the supplemented groups than in Con group. T he disease resistance was significantly increased in the supplemented groups than in Con group (Figure 1).
T his study suggests that dietary supplementation of manna oligosaccharides, L. plantarum, B. subtilis and B. licheniformis could increase the innate immunity and disease resistance against E. tarda in growing olive flounder.