Effect Of Dietary Fructo And Mannan Oligosaccharides And Bacillus Clausii Administration On Non-specific Immune And Intestinal Microflora Of Japanese Flounder (Paralichthys Olivaceus)

A feeding experiment was conducted to investigate the effect of dietary fructo and mannan-oligosaccharides (FOS and MOS), and Bacillus. clausii administration on non-specific immune and intestinal microflora in healthy juvenile Japanese flounder (Paralichthys olivaceus). Eight experimental diets (Diets T0-T7) were designed to contain different concentrations of FOS, MOS and B. clausii (i.e. Diet T0, control; Diet1, 0.5%FOS; Diet 2, 0.5%MOS; Diet 3, 0.25%FOS + 0.25%MOS; Diet 4, B. clausii; Diet 5, 0.5%FOS + B. clausii; Diet 6, 0.5%MOS + B. clausii; Diet 7, 0.25%FOS + 0.25%MOS + B. clausii). The juvenile Japanese flounder were randomly divided into 8 groups with 3 replicate tanks of 20 fish each. Fish were fed hand-fed to apparent satiation twice daily for 56 d. The results of the growth performance, non-specific immune and intestinal microflora of Japanese flounder were presented as follows:(1) Dietary FOS, MOS and/or B. clausii administration could promote growth performance of Japanese flounder, and fish fed the diet containing FOS, MOS and B. clausii together had the best effect (P<0.05). There was no significant difference in growth performance among the three dietary treatments (i.e. FOS, MOS and B. clausii addition into the diets alone). Fish in 0.5%FOS + B. clausii group had better weight gain(P>0.05) and feed conversion(P<0.05) compared with 0.5%FOS and B. clausii groups, but fish in 0.5%MOS + B. clausii group did not showed any improvement compared with 0.5%MOS and B. clausii groups. This indicated an obvious synergy between FOS and B. clausi. The dietary B. clausii administration alone significantly increased the hepatopancrea somatic index of Japanese flounder as compared with other dietary treatments (P<0.05). Dietary FOS, MOS and/or B. clausii administration had no significant effect on condition factor of Japanese flounder (P>0.05). The activities of intestinal protease and amylase of fish in 0.5%FOS,0.5%MOS and B. clausii groups were silightly higher than the control (P>0.05). However, the activities of intestinal protease and amylase in fish fed the diets containing FOS, MOS and/or B. clausii significantly higher than that of the control (P<0.05). Dietary FOS, MOS and B. clausii administration had no effect on the activities of hepatic protease and amylase of Japanese flounder (P>0.05). Dietary FOS and/or MOS addition with B. clausii significantly increased body protein content but decreased body lipid content of Japanese flounder (P<0.05). (2) The serum lysozyme activity was significant higher in Japanese flounder fed the B. clausii contained diets than that of those fed other diets (P<0.05). Serum lysozyme activities of fish fed 0.5%FOS and 0.5%MOS diets were not significantly different from that of the control (P>0.05). The results suggested that dietary B. clausii was accounted for the increase in the serum lysozyme activity. The serum acid phosphatase activities were significantly higher in additive treated groups than that of the control (P<0.05), except 0.5%FOS group. However, Dietary FOS, MOS and B. clausii administration had no significant effect on phagocytic activity of Japanese flounder (P>0.05). The serum triglyceride concentration was significantly lower in the group fed the diets containing B. clausii with FOS or MOS than that of the control (P<0.05), but serum total cholesterol concentration was not different from the control (P>0.05). The low density lipoprotein cholesterol concentrations were significantly lower in the fish fed the 0.5%FOS diet and B. clausii + 0.5% FOS diet than that of the control (P<0.05).(3) The number of total heterotrophs and pathogens Staphylococcus epidermidis, Vibrio furnissii, and Acinetobacter baumannii in the intestine of Japanese flounder in dietary FOS, MOS and B. clausii administrated groups significantly decreased compared with control, and Pseudomonas putida and Vibrio parahaemolyticus were not detected in these groups. The percentage of A. baumannii in bacteria was lower in the gut of the fish fed the B. clausii contained diet than that of fish fed the other diets. Dietary FOS, MOS and B. clausii administration together significantly decreased the number of total heterotrophs and pathogens Staphylococcus epidermidis, Vibrio furnissii and Acinetobacter baumannii in the gut of Japanese flounder as compared with dietary FOS, MOS and B. clausii administration alone.