| We study the three kinds of composite probiotics,which added to the feed and fed healthy tilapia, explore the mechanism of preliminary composite probiotics that enhance Tilapia’s immunity, from the molecular level, Determine the best set of the three complex probiotic group,which have a good effect in enhancing the immune protection rate.Test is divided into four groups, one for the control group. Three experimental groups were fed tilapia with the feed that were added with Bacillus lincheniformis+ Bacillus subtilis. Bacillus lincheniformis+Bacillus coagulans, Bacillus lincheniformis+Enterococcus faecalis. Three fish in each group were collected liver, kidney, head kidney, spleen and gills every 10 days,using real-time quantitative PCR technology to detect that the relative expression of three immune-related gene changes,including Cyclooxygenase-2(COX-2), interleukin-lβ(IL-lB), tumor necrosis factor-a(TNF-a). After forty days, In order to detect changes in the rate of protection against infection of tilapia,we injected with pathogens into tilapia. Including Aeromonas hydrophila, Aeromonas veronii and Streptococcus agalactiae,which are common pathogens of tilapia. The injection site is at the base of the pectoral fin tilapia.The results showed that:All of the three composite probiotics were significantly (P<0.05) induced the expression of COX-2 IL-1β and TNF-a gene in the five organs of tilapia, The group of Bacillus lincheniformis and Bacillus subtilis showed the earliest induction effect.Induced gene expression levels were more significant in the immune organ containing kidney, head kidney and spleen than it in the non-immune organ containing liver and gills; The group of Bacillus lincheniformis and Bacillus subtilis increased infection protection rate of tilaia to Aeromonas hydrophila，eromonas veronii and Streptococcus agalactiae. The group of Bacillus lincheniformis and Bacillus coagulans increased infection protection rate of tilaia to Aeromonas hydrophila.Aeromonas veronii. |
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