| Bacitracin Methylene Disalicylate(BMD)is a metabolite of Bacillus licheniformis secondary metabolic bacitracin and methylene salicylic acid,and has a strong effect on Gram-positive bacteria and inhibits bacterial cell wall of the synthesis,killing bacteria,with the role of immunity improving,the FDA has issued a document approved methylene salicylic acid bacteria as a veterinary drug ingredient for feed.Bacitracin Zinc(BZ)as a first-generation bacitracin feed additive,has been widely used in aquaculture production,but has been banned by the state.In the production of rabbits,whether bacitracin methylene disalicylate has the same effect of bacitracin zince was no reported.In this paper,different levels of BMD were added to the diets,and BZ was used as positive control to detect the effect of BMD on blood and intestinal immune indexes and related immune gene expression in young rabbits.And to provide the theoretical basis for the application of BMD in rabbit production.A total of 300 New Zealand white rabbits were randomly divided into five groups,each treated with 3 replicates,20 replicates each,BMD high group(BMD H,100 mg/kg),BMD middle group(BMD M,50 mg/kg),low dose group(BMD L,25 mg/kg),BZ control group(BZ,50 mg/kg),blank control group(C,no addition)The test period is 35 d.The results were listed as follows:1.Dietary supplementation of BMD and BZ in young rabbits,serum total protein(TP)and glucose(GLU)were higher than the C group,there were no significant difference in TP between BMD group and BZ group(P>0.05),and the GLU of BMD H group,BMD M group,and BZ group were no significant difference(P>0.05).The levels of alkaline phosphatase(AKP)and urea nitrogen(BUN)in BMD group and BZ group were lower than those in C group,and BMD H group was significantly lower than that in C group(P<0.05)and BMD H group,BMD M group,BZ group were no significant difference(P>0.05).The serum levels of IgG in BMD H and BMD M group were significantly higher than those in BZ group and C group(P<0.05),but there were no significant difference in IgM in the all groups(P>0.05).The levels of TNF-a.IL-2 and IL-6 in BMD H group,BMD M group and BZ group were signifycantly higher than those in C group(P<0.05),and BMD H group was signifycantly higher than BZ group.The levels of superoxide dismutase(SOD)in the serum of BMD H group,BMD M group and BZ group were significantly higher than those in the C group(P<0.05),and the total antioxidant capacity(T-AOC)in the serum of BMD group were significantly higher than those in the C group(P<0.05);The content of malondialdehyde(MDA)was significantly lower than that of C group(P<0.05),and there were no significant difference between BMD group and BZ group(P<0.05).2.The contents of IgG,TNF-??IL-2 and IL-6 in cecum and duodenum of rabbits in BMD group and BZ group,were higher than those in the C group,and the BMD H group and the BZ group were significantly higher than the C group(P<0.05),and there were no significant difference between BMD H group and BZ group(P>0.05).The BMD H group in the duodenum was significantly higher than that in the C group(P<0.05),and the contents of IL-2 and IgG in BMD H group and BMD M group were significantly higher than the BZ group(P<0.05)The levels of T-AOC,SOD and catalase(CAT)in cecal and duodenum of BMD H group and BZ group were significantly higher than those in C group(P<0.05),and there were no significant difference between BMD group and BZ group(P<0.05);the contents of MDA in cecal and duodenum of BMD H group were significantly lower than C group(P<0.05),and there were no significant difference between BMD group and BZ group(P<0.05).3.The expression levels of cytokines IL-2 in the cecum and duodenum were detected and find the expression levels of the BMD and BZ groups were increased,and the expression of IL-2 gene in BMD H group was significantly higher than that in C group(P<0.05).The expression of IgG gene in the BMD group and BZ group were significantly higher than that in the C group(P<0.05),and the expression of IgG gene in the BMD H group was significantly higher than BZ group(P<0.05).The expression levels of a-defensin gene(NP-5)in the cecal and duodenal of BMD group and BZ group were signifycantly higher than the C group(P<0.05),the expression levels of NP-5 in BMD group was significantly higher than the BZ group in the cecum(P<0.05),and there were no significant difference between BMD group and BZ group in the duodenum(P>0.05).There was a significant positive correlation between the level of IL-2 in the cecum and duodenum(P<0.05),and the level of IgG in the cecum was positively correlated with the gene expression level(P<0.05).In summary,the dietary supplementation of methylene salicylic acid bacitracin and bacitr-acin zinc,can enhance the immune performance of young rabbits,methylene salicylate peptide can be modified bacitracin zinc,and 50-100mg/kg feed additive is the best. |
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