| This article aims to study the effect of Bacillus cereus PAS38 preparation added to basal diets on growth performance,immune organ index,intestinal digestive enzyme activity,bacterial diversity,serum cytokines and immune-related gene expression of broilers.80 AA broiler chickens aged 1 day were randomly divided into2 groups with 4 replicates in each group and 10 chickens in each replicate.The control group was fed the basal diet.The experimental group added 0.5 g/kg of Bacillus cereus PAS38 preparation to the basal diet.The test period was 42 days without any immunization.The growth performance was observed during the whole period.Samples were taken on the 28 th and the 42 nd day to measure intestinal digestive enzyme activity,intestinal flora diversity,immune organ index,serum immunoglobulin content,serum cytokines level,and immune-related gene expression.The result is as follows:1.All the chickens were weighed in vivo and found that the body weight and net weight gain of the broiler chickens in the experimental group were higher than those in the control group.The difference in body weight was significant at the 28 th day(P<0.01).The feed weight was lower than that of the control group.However,the difference was not significant(P>0.05).The organs of the spleen,thymus and bursa were weighed and tested for immune organ index.The results showed that the index of immune organs in the test group was increased compared with the control group,and the thymus index and spleen index were significantly different on the 28 th day(P<0.05),and extremely significantly different on 42 d(P<0.01),and there was a significant difference on the 42 d of Bursa's index(P<0.05).2.The activities of amylase and neutral protease in the ileum and jejunum of the test group were higher than those in the control group,but only 28 days had significant differences in jejunum amylase activity and ileal neutral protease activity(P<0.05).The rest did not differ significantly(P<0.05).3.The analysis of diversity,evenness,and richness of the caecal flora was performed using PCR-DGGE.The results showed that the Shannon index andevenness of the experimental group were higher than the control group on the 28 th day,and the difference was significant(P<0.05).The data of the other items in the experimental group was also higher than the control group,but the difference was not significant(P>0.05).At the age of 28 days and 42 days,the similarity of the caecal flora in the experimental group was 4% and 3% higher than that in the control group,respectively.4.Separation of blood serum from the wing veins and the use of cellulose acetate membrane electrophoresis to detect serum immunoglobulin content.The results showed that the content of the experimental group was higher than that of the control group,and the difference was not significant(P>0.05).Serum levels of cytokines were detected by ELISA kits.IL-2 and IFN-? levels were higher in the experimental group than in the control group,but the difference was not significant(P>0.05).5.Real-time fluorescent quantitative PCR assay was used to detect the transcription level of mRNA of immune-related genes in thymus and bursa of Fabricius.The results showed that except IL-4 and IL-10 mRNA in the test group,the transcription level was lower than that in the control group.IL-2,IFN-?,GBP1,and IRF1 mRNA transcription levels were higher in the two immune organs and two days of age than in the control group.The transcription level of IRF1 mRNA in the test group in the 42 nd day in the bursa of Fabricius and thymus was significantly different from that in the control group(P<0.05);the IL-10 mRNA at the 42 nd day was significantly higher in the thymus transcription level in the experimental group than in the control group.(P < 0.01).The results showed that adding 0.05% of Bacillus cereus PAS38 to broiler diets can promote broiler growth,increase intestinal digestive enzyme activity,immune organ index,serum immunoglobulin content and serum cytokine levels.It also promoted the expression of immune up-regulated genes and inhibited the expression of immune down-regulated genes,which in turn proved that the preparation of Bacillus cereus PAS38 can improve the immune function of broilers. |
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