Effects Of Dietary Potassium Diformate , Xylo-oligosaccharides And Inulin On Growth, Immune Responses And Resistance Against V.splendidus Of Sea Cucumber Apostichopus Japonicas Selenka

Three feeding trials were conducted in indoor circulating system to investigate the effects of dietary potassium diformate, xylo-oligosaccharides and inulin on growth, immunity and disease resistance of sea cucumber (Apostichopus japonicus Selenka). The results were summarized as follows:1.A 8-week feeding experiment was conducted to investigate the effects of dietary potassium diformate on growth, immune responses, intestinal mircroflora and disease resistance of sea cucumber Apostichopus japonicas Selenka (mean initial body weight 2.13±0.03g). Potassium diformate was supplemented into the basal diet to formulate seven isonitrogenous and isoenergetic practical diets containing 0.00% (the control diet), 0.2%, 0.4%, 0.6%, 0.8%, 1.0% and 1.2% potassium diformate of dry weight, respectively. The results showed that there was no mortality observed during the feeding trial. The specific growth rate (SGR) of sea cucumber was significantly enhanced by the supplementation of potassium diformate in diets. Sea cucumber fed diets with 1.0% and 1.2% potassium diformate showed significantly higher SGR compared to the control group (P<0.05). The immune function assay showed that dietary supplementation of 1.0% and 1.2% potassium diformate significantly increased the coelomocytes phagocytosis and the active oxygen species production compared to other treatments (P<0.05). No significant difference among dietary treatments were observed in superoxide dismutase and nitric oxide synthase (P>0.05). The Vibiro spp. counts in sea cucumber fed diets with 0.4%, 0.6%, 0.8%, 1.0% and 1.2% potassium diformate were significantly lower than the control group (P<0.05). However, the total viable bacterial counts were independent of dietary treatments. The challenge experiment with V. splendidus showed that 14-day cumulative mortality in sea cucumber fed the control diet (46.67%) and 0.2% potassium diformate (38.33%) was significantly higher than those in sea cucumber fed diets with 0.4%, 0.6%, 0.8%, 1.0% and 1.2% potassium diformate (P<0.05).2. A 8-week feeding experiment was conducted to investigate the effects of dietary xylo-oligosaccharides on growth, immune responses, intestinal mircroflora and disease resistance of sea cucumber Apostichopus japonicas Selenka (mean initial body weight 2.13±0.03g). Xylo-oligosaccharides was supplemented into the basal diet to formulate seven isonitrogenous and isoenergetic practical diets containing 0.00% (the control diet), 0.02%, 0.04%, 0.06%, 0.08%, 0.10% and 0.12% xylo-oligosaccharides of dry weight, respectively. The results showed that there was no mortality observed during the feeding trial. The specific growth rate (SGR) of sea cucumber was significantly enhanced by the supplementation of xylo-oligosaccharides in diets. Sea cucumber fed diets with 0.06%,0.08%, 0.10% and 0.12% xylo-oligosaccharides showed significantly higher SGR compared to the control group (P<0.05). The immune function assay showed that dietary supplementation of 0.10% and 0.12% xylo-oligosaccharides significantly increased the superoxide dismutase activity compared to the control and the dietary supplementation of 0.10% and 0.12% xylo-oligosaccharides significantly increased the nitric oxide synthase activity compared to other treatments (P<0.05). Increasing trends were observed in the coelomocytes phagocytosis and the active oxygen species production though there were no significant differences among dietary treatments in the coelomocytes phagocytosis and the active oxygen species production (P>0.05).The total viable bacterial counts in sea cucumber fed diets with 0.10% and 1.2% xylo-oligosaccharides were significantly higher than the control group (P<0.05). However, the Vibiro spp. counts were independent of dietary treatments. The challenge experiment with V. splendidus showed that there were no significant differences in 14-day cumulative mortality among dietary treatments (P>0.05). But with the increase of dietary xylo-oligosaccharides levels, 14-day cumulative mortality of sea cucumber decreased. The lowest 14-day cumulative mortality was found in sea cucumber fed 0.10% xylo-oligosaccharides. 3.A 8-week feeding experiment was conducted to investigate the effects of dietary inulin on growth, immune responses, intestinal mircroflora and disease resistance of sea cucumber Apostichopus japonicas Selenka (mean initial body weight 2.13±0.03g). Inulin was supplemented into the basal diet to formulate seven isonitrogenous and isoenergetic practical diets containing 0.00% (the control diet), 0.1%, 0.3%, 0.5%, 0.7%, 1.0% inulin of dry weight, respectively. The results showed that there was no mortality observed during the feeding trial. The specific growth rate (SGR) of sea cucumber was significantly enhanced by the dietary supplementation of inulin and sea cucumber fed 0.7% and 1.0% inulin showed the highest SGR. The immune function assay showed that dietary inulin supplementation increased the superoxide dismutase activity (P<0.05) and the nitric oxide synthase activity compared to other treatments (P<0.05). Sea cucumber fed diets with 0.7% and 1.0% inulin showed increased activities of both these two enzymes compared to the control group. Increasing trends were observed in the coelomocytes phagocytosis and the active oxygen species production with the increase of dietary inulin and the 1% inulin supplementation group showed the highest values. The total viable bacterial counts in sea cucumber fed diets with 0.7% inulin were significantly higher than the control group (P<0.05) and the Vibiro spp. counts in sea cucumber fed diets with 0.5% inulin were significantly lower than the control group (P<0.05). However, there were no differences among the other treatments. The challenge experiment with V. splendidus showed that 14-day cumulative mortality decreased with the increase of dietary inulin and 14-day cumulative mortality in sea cucumber fed the diet with 1.0% inulin was significantly lower than the other treatments.