Effect Of Bacillus On Fish Immune Function

This paper dealed with the effects of Bacillus sp. as food additive on the immune function of grass carp and common carp, and on the intestinal microflora of grass carp.In the test to study the effct of Bacillus on the immune function of grass carp, the concentrations of Bacillus in four groups were respectively 1.0×10¹1 cfu/kg feed (group B₁), 3.0×10¹1 cfu/kg feed (group B₃), 5.0×10¹1 cfu/kg feed (group B₅) and 0 cfu/kg feed (group Bo). The phagocytic activity of leukocytes, lysozyme activity in serum, transicmation rate of lymphocytes (SI) and number of the intestinal intraepithelial lymphocytes (iIEL) of grass carp were tested. The results showed: (1) Bacillus of 1.0× 10¹1 cfu/kg feed, 3.0×10¹1 cfu/kg feed, 5.0×10¹1 cfu/kg feed all could reprove the phagocytic activity of leukocytes and lysozyme activity. Thereby Bacillus could strenghen the unspecific immune function of grass carp. The effect in group B₃ and group B₅ were best; (2) After Bacillus was fed for 14ds-35ds, SI in the group B₁, group B₃ and group B₅ ascend slightly in some time, but this effect couldn't last long; (3) When the concentration of Bacillus were 3.0×10¹1 cfu/kg feed, 5.0×10¹1 cfu/kg feed, the relative number of iIEL of grass carp increased significantly.In the test to study the effct of Bacillus on the immune response of common carp, the fish were immunized in group bo, group b₁, group b₃, group b₅; the fish weren't immunized in group B₀, group B₁, group B₃, group B₅. The concentration of Bacillus in group b₁ and group B₁ is 1.0×10¹1 cfu/kg feed; which in group b₃ and group B₃ is 3.0× 10¹1 cfu/kg feed; which in group b₅ and group B₅ is 5.0×10¹1 cfu/kg feed. The feed of group b₀ and group B₀ didn't contain Bacillus. The phagocytic activity of leukocytes, lysozyme activity in serum, transicmation rate of lymphocytes(SI), agglutinating antibody titer in the serum and relative percent survival (RPS) of carp were tested. The results showed:(1) Bacillus of of 1.0×10¹1 cfu/kg feed, 3.0×10¹1 cfu/kg feed, 5.0×10¹1 cfu/kg feed all could reprove the phagocytic activity of leukocytes and lysozyme activity; (2) Being different from the effect of Bacillus on the SI of grass carp, Bacillus of 1.0×10¹1 cfu/kg feed, 3.0×10¹1 cfu/kg feed, 5.0×10¹1 cfu/kg feed all could reprove SI of carp. When the concerntration of Bacillus is 5.0×10¹1 cfu/kg feed, SI is the highest; (3) Bacillus could reprove agglutinating antibody titer of common carp. When the concerntration of Bacillus is 5.0×10¹1 cfu/kg feed and the feeding time is 21^th day, the mean agglutinating antibody titer immunized common carp is the highest that is 456.1; (4) Bacillus could reprove the survival rate of common carp after challenged with live Ahydrophila. When he concerntration of Bacillus is 5.0×10¹1 cfu/kg feed, the RPS ofimmunized common carp is the highest.In the test to study the effct of Bacillus on the changes in the intestinal microflora of grass carp, the concentrations of Bacillus in four groups were respectively 1.0 X 10u cfu/kg feed (group Bi), 3.0 X1011 cfu/kg feed (group B3), 5.0 X 10ncfu/kg feed (group B5) and 0 cfu/kg feed (group Bo). The results showed: (1) After feeding Bacillus, the numbers of the whole intestinal microflora of carp increased firstly, then declined subsequently; the difference wasn't significantly in the group Bo, group Bj, group B3 and group B5 after feeding without Bacillus; (2) After feeding Bacillus, the predominant intestinal flora of carp was Aeromonas, Enterobacteriaceae, Bacillus, Vibrio, Acinetobacter and Coynebacteriumr; (3) After feeding Bacillus, the percentage of Aeromonas and Enterobacteriaceae declined; the percentage of Bacillus increased. But the percentage of Aeromonas and Enterobacteriaceae increased and the percentage of Bacillus declined after feeding without Bacillus. However, the percentage of Aeromonas always remain 17% upwards, and the percentage of Enterobacteriaceae always remain 11% upwards in spite of eating Bacillus or not.