This work explores the effects of dietary Radix Rehmanniae Preparata polysaccharide (RRPP) supplementation on the growth performance, nonspecific immune responses, immune- and growth-related gene expression and disease resistance to Aeromonas hydrophila in Luciobarbus capito. Diets containing five concentrations of 0%, 0.05%, 0.1%, 0.2% and 0.4% RRPP were fed to fish for 60 d. The results indicated that the growth performance significantly increased in the 0.1%, 0.2% and 0.4% RRPP groups compared with that in the control (P < 0.05). The activities of serum lysozyme (LAZ), acid phosphatase (ACP), superoxide dismutase (SOD), alkaline phosphatase (AKP) and total protein (TP) were significantly increased in the appropriate RRPP supplemented groups (P < 0.05). With respect to immune- and growth-related genes, such as interleukin (IL)-1β, IL-8, tumor-necrosis factor (TNF)-α, interferon (IFN)-γ, growth hormone (GH), insulin-like growth factor (IGF)-I and IGF-II, up-regulation were observed in the three organs (kidney, spleen, gut) of the fish fed with RRPP, compared with the control. In contrast, the mRNA expression of IL-10 and transforming-growth factor (TGF)-β were downregulated. After challenge with A. hydrophila, the final survival rate was significantly higher in fish fed the RRPP supplement than that in the control group (P < 0.05). In conclusion, RRPP enhanced the growth performance, immune response and disease resistance of Luciobarbus capito, with the greatest effects at 0.2% RRPP.
Keywords: Disease resistance; Immune response; Luciobarbus capito, growth performance; Radix Rehmanniae Preparata polysaccharides.
Copyright © 2019. Published by Elsevier Ltd.