| This feeding study was performed to investigate effects of different levels of rare earth-chitosan chelate (RECC) on nonspecific immunity, body biochemical component and intestinal microoranism of Carassius auratus. There were 4 dietary treatments: a control group and three RECC-treated which were fed with 800mg, 1600mg and 2400mgRECC per kg feed respectively. Each group has 35 fishes with 5 duplicates in the present trial. The whole feeding period lasted for 60 days. The nonspecific immunity indexes were measured on 20th, 40th, and 60th d; at the end of the experiment, analysis on flesh quality and intestinal microflora diversity of Carassius auratus. Results were shown as follows:1. On 20th day, the levels of serum and spleen lysozyme activity of three RECC-treated groups were all higher than that of control group; and moreover, compared with the control group, the 0.24% RECC group had significant variation (P<0.05)on serum lysozyme activity. Serum, spleen and head kidney SOD activity of three RECC-treated groups have a certain degree of increase (P>0.05). Three RECC-treated groups had a improvement compare with control group on spleen index and head kidney index, and the value of spleen index of 0.24% RECC group was even significant higher than that of other groups (P<0.05). But on 40th and 60th, the lysozyme activity, SOD activity, spleen index and head kidney index showed that data were approximate among all groups (P>0.05).2. In this study, the crude protein contents of muscle of three RECC-treated groups were increased or closed to that of the control group (P>0.05); Crude fat contents were all higher than that of the control group, and moreover, there was a significantly difference between 0.16% RECC group and other three groups (P<0.05). RECC added in diet can increase inosine and inosinic content and decreas cholesterol content in muscle of C. auratus. Inosine content of 0.16% RECC group was higher of 49.84% than that of control group (P<0.05).3. Total DNA of intestinal tract bacteria from Carassius auratus intestinal was extracted to investigate intestinal microflora. The intestinal substance of fish was taken as sample to precipitate bacteria through PBS cleaning and centrifuge. Using Bacterial DNA Kit to extraction intestinal tract bacteria total DNA, water was culitivated as negative control group. DNA extract of four groups was examined by agarose gel electrophoresis, the results showed that: DNA band was bright, clear, tidiness and non-degeneration phenomenon. There was no DNA band appeared in negative control group. It was indicated that the DNA samples can be used subsequent test. The 16S rDNA was amplified from these DNA samples through a set of bacteria-specific primers, obtained the clear atlas and neatly bands, the length of the DNA fragment successfully amplified here was about 450bp. There were no non-specific products and primer dimmer in products. Length and concentration of the DNA fragment accorded with requirements.4. By SSCP electrophoresis, there were 39 bands in SSCP map. Control group, 0.08% RECC group, 0.16% RECC group and 0.24%RECC group had 20, 22, 26 and 21 bands respectively. Band 6th, 12th, 24th, 28th, and 29th occurred in each group, but the gray scal of these bands was various. Each group had its specific bands in SSCP map. The value of the Shannon-Wiener indexes of the three RECC-treated groups was 4.19, 4.39 and 4.36 respectively, all higher than that of control group (3.65). The values ofβc index between control group and 0.08% RECC group, 0.08% RECC group and 0.24% RECC group were higher, but were lower among other groups. The values of the Cs index between control group and 0.08% RECC group, 0.08% RECC group and 0.24% RECC group were lower, but were higher among other groups.
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