| In this experiment,two strains antagonistic to Flavobacterium columnarus were isolated and screened and identified from pond water The selected two probiotics were mixed with the basic feed to prepare three different probiotic feeds:basic feed(control group T0),added base feed of Bacillus amyloliquefaciens(treated group T1),and added The basic diet of Bacillus(treated group T2)and the mixed group of Bacillus amyloliquefaciens and Acinetobacter johnsonii(treated group T3)were fed for 40 days,and their effects on growth performance,serum biochemical indexes and immune indexes of Carassius auratus were tested.1.Isolation,identification and screening of antagonistic bacteria.For the pathogenic Flavobacterium,several strains of antagonistic bacteria were isolated from the pond water.As determined by 16S r DNA sequence analysis,they were identified as Bacillus amyloliquefaciens and Acinetobacter johnsonii.The acid resistance,bile tolerance and growth characteristics of the two strains were studied.The effects of B.amyloliquefaciens and A.johnsonii on the growth performance,serum biochemical indexes and immune indexes of C.auratus were added.After 40 days of feeding,the results showed that serum total bilirubin and direct bilirubin levels in the T1 group were lower than those in the control group(p<0.05).In addition,serum indirect bilirubin content and gluten/gluten in the T2 group were lower than those in the control group(p<0.05).In immunology,the serum Ig G content of the mixed bacteria T3 group was higher than that of the control group T0(p<0.05).The alkaline phosphatase activity of the three treatment groups was significantly higher than that of the control group(p<0.05).Compared with T0,the levels of high-sensitivity C-reactive protein in the T1 and T2 groups were significantly lower(p<0.05).The addition of A.johnsonii significantly reduced the malondialdehyde content in the T2 group(p<0.05).There was no difference in superoxide dismutase in serum.The results showed that B.amyloliquefaciens and A.johnsonii added to the feed could increase serum immunoglobulin levels and some non-specific immune parameters,and A.johnsonii could also enhance the antioxidant capacity of C.auratus.3.The effect of intraperitoneal injection of B.amyloliquefaciens and A.johnsonii on serum immune index of C.auratus.After 24 hours,48 hours and 96 hours of injection of sterile saline and mixed bacterial solution(1:1)of 1×10~6,1×10~7,1×10~8,1×10~9(CFU/m L)and two kinds of 1×10~8(CFU/m L)monobacterial solution.In terms of serum immunoglobulin M,there was no significant difference between the treated group and the control group at any time(p>0.05),and in the aspect of alkaline phosphatase,there was no significant difference at the level of alkaline phosphatase after 24 hours(p>0.05).But after 48 hours,the alkaline phosphatase level of the two groups was higher than that of the control group(p<0.05).In the aspect of serum aspartate aminotransferase and alanine aminotransferase,after 24 hours,the contents of aspartate aminotransferase and alanine aminotransferase in treated groups were lower than those in the control group(p<0.05),but there was no significant difference in aspartate aminotransferase and alanine aminotransferase after 48 hours and 96 hours.In this paper,two antagonistic antibacterial strains against Flavobacterium columnarus were screened and identified as B.amyloliquefaciens and A.johnsonii.Two kinds of bacteria were added to the feed to feed the C.auratus,and the growth performance and immune index of the C.auratus were tested after the 40-day culture period,in order to develop probiotics with potential for aquaculture. |
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