Effect of -glucooligosaccharides as a new prebiotic for dietary supplementation in olive flounder (Paralichthys olivaceus) aquaculture

beta-Glucooligosaccharides (BGO), produced from barley -glucan, were used as a feed supplement (0.1%) for juvenile olive flounder (Paralichthys olivaceus) to identify and quantify its oral administration effects on innate immunomodulation and infectious disease protection. Juvenile flounders (14 +/- 0.5g) were divided into two groups fed either 0.1% BGO (treatment) or a standard diet (control) for 8weeks. At the end of the experiment, investigation of the effects was carried out through systemic studies on growth performance, serum and mucus biochemical parameters, innate immunity, microvillus length, and relative pro-inflammatory cytokine gene expression. The results demonstrated that the BGO diet produced slightly higher levels of growth performance, serum protein, microvillus length and pro-inflammatory cytokine gene (tumour necrosis factor-, interleukin [IL]-1, and IL-6) expression without any significant differences (p>.05). All innate immunity parameters were up-regulated by BGO administration and, among these, respiratory burst, lysozyme and superoxide dismutase (SOD) were significantly different (p<.05). Fish in the both groups were challenged with Streptococcus iniae (1.35x10(8) CFU/ml), and BGO group was focused to confirm the promotion of innate immunity parameters. The results showed a significantly (p<.05) lower death rate compared with that of the control. Therefore, BGO could be used as a new prebiotic in future olive flounder aquaculture as well as to control streptococcosis.