Effects Of Antimicrobial Peptide Cecropin On Growth,Immunity And MRNA Expression Level Of Related Cytokine In Young Roosters For Egg Production

This experiment is conducted to investigate the effects of antibacterial peptides on growth performan-ce,immune function,intestinal flora,intestinal mucosal morphology,mucosal immunity and mRNA express-ion of proinflammatory cytokines in young roosters for egg production.Three hundred and thirty-six young roosters for egg production were selected, and randomly divided into seven treatment groups with four replicates in every group, with twelve chicks in every replicate. The seven treatment groups were control group, antibiotics group, and ABPs groups, respectively. The feeding experiment lasted for42days.The experiment consists of three parts,the results showed as following:(1) The ADFI of ABPs groupⅢ,Ⅳ,Ⅴwere significantly lower than that in control group(P<0.05), ADG had no significant difference among each treatment group(P>0.05), F/G of ABPs groupⅣ,Ⅴwas significantly lower compared with that in control group(P<0.05).(2) The thymus index of ABPs group V was significantly higher than that in other treatment groups (P<0.05), the cloacal bursa index was significantly higher compared with that in control group and ABPs group I (P<0.05), the spleen index of ABPs groupⅣ,Ⅴhad no significant difference(P>0.05), but it increased significantly compared with that in other treatment groups(P<0.05).(3) IL-6relative expression level of ABPs group V decreased significantly compared with that in other treatment groups(P<0.05), the expression level of IFN-y of ABPs groupⅢ,Ⅳ,Ⅴwas significantly lower than that in control group(P<0.05). TNF-α expression level of ABPs groupⅣ,Ⅴdecreased significantly compared with that in control group(P<0.05).(4) IgA level of ABPs groupⅣ,Ⅴwere significantly higher than that in control group and antibiotics group(P<0.05), IgG level of ABPs group Ⅱ,Ⅲ,Ⅳ,Ⅴ increased significantly compared with that in control group and antibiotics group(P<0.05). The C3level of the ABPs add groups were significantly higher than that in control group and antibiotics group(P<0.05).Lysozyme level of antibiotics group,ABPs group Ⅲ,Ⅳ,Ⅴwere significantly increased than that in control group(P<0.05). IgM,C4level had no significant difference among each treatment group(P>0.05).(5) The number of escherichia coli of control group decreased significantly compared with that in ABPs groups(P<0.05),the number of bifidobacterium of ABPs group Ⅱ,Ⅲ,Ⅳ,Ⅴ increased significantly compared with that in control group and antibiotics group(P<0.05),the number of lactobacillus of ABPs groupIV, V were significantly higher than that in control group(P<0.05).(6) The epithelial mucous membrane structure of duodenum,jejunum and ileum of ABPs group were integrated compared with that in control group, crypt depth of duodenum, thickness of muscularis of jejunum had no significant difference among each treatment group(P>0.05). Villus height、thickness of intestinal mucosa、thickness of muscularis of ABPs groups were significantly higher than that in control group(P<0.05), ABPs group V had a best effect.Scanning electron microscope (SEM) results showed that adding certain ABPs to the diet can make microvilli of jejunum more regular than that in control group, the effects of ABPs group V more significant.The intraepithelial lymphocyte of jejunum of ABPs group V were significantly higher than that in control group(P<0.05), the number of goblet cells of ABPs groupⅢ,Ⅳ,Ⅴin the small intestine increased significantly compared with that in control group(P<0.05).Adding different level of antibacterial pepitides to the diet can improve the production performance and immunity of young roosters for egg production, increase the number of bifidobacterium and lactobacillus of intestinal probiotics,and decrease effectively the number of escherichia coli of pathogenic bacteria, decrease mRNA expression level of proinflammatory cytokine in young roosters for egg production to some extent,improve significantly mucous membrane of small intestine morphology, and increase the number of immune active cells. Together,The optimal additive amount was ABPs group Ⅴ(350mg/kg).