Effect Of Anti-peptide CC31 Monomer And Tandem Peptide On Small Intestine Growth,Development,Immunity And Caesal Microbiota Of Lamb

Lamb weaning stress is a serious problem that has plagued the development of China's sheep industry.Antimicrobial peptides have a small molecular weight and provide safe and stable protection for a variety of organisms in the natural world.It has a unique membrane-breaking bactericidal mechanism and is not likely to cause bacterial resistance,so it provides a new solution to reducing weaning stress.The test uses a single factor test design method.48 seven-day-old lambs were selected and divided into 4 groups according to the principle of similar body weight(3 replicates per group,4 per replicate).Monopeptides were fed to the basal diet supplemented with 300 mg/kg monomer peptide,tandem peptides were fed to the basal diet supplemented with 300 mg/kg tandem peptide,and antibiotics were fed to the basal diet supplemented with 300 mg/kg antibiotics The blank group was fed the basal diet and the trial period was 28 days.At lambs 14,21,28,and 35 days of age,one lamb was randomly selected for slaughter in each replicate.Histological techniques were used to study the morphological structure of small intestine tissue and mucous membrane.Relative fluorescence quantitative PCR was used to study the expression level of tight junction protein in intestinal epithelium and the expression levels of immune receptor and immune cytokines in liver tissue.The ELISA enzyme-linked immunosorbent assay kit was used to detect the content of immunoglobulin in the serum,and high-throughput sequencing was used to study the structure of the intestinal colonic flora.The results showed that: 1.Diets containing CC31 monomer peptide and tandem peptide significantly increased duodenum,jejunum and ileum villus height,gill ratio and villous surface area and significantly decreased crypt depth(P<0.05).2.The monomeric peptide group significantly increased the expression of ZO-1 gene in the duodenum(P<0.05).The monomeric peptide group had a tendency to increase the relative expression of Claudin-1 gene(P>0.05).Antibiotic group,tandem peptide group and monomeric peptide group significantly increased the relative expression of ZO-1 gene in jejunum(P<0.05).Monopeptide group and antibiotic group significantly increased the relative expression of Claudin-1 gene in jejunum(P< 0.05),tandem peptide group increased the relative expression of Claudin-1 gene in jejunum(P>0.05),monomer peptide group increased the relative expression of ZO-1 gene in ileum(P>0.05).3.With the increase of age,the content of immunoglobulin Ig A,IgG,and IgM in lamb serum increased significantly.The tandem peptide group and monomer peptide group both significantly increased the serum Ig A content(P<0.05),and there was no significant difference(P>0.05)from the antibiotic group.The monomeric peptide group significantly increased the IgG content(P<0.05),and the tandem peptide group had a tendency to increase the IgG content(P>0.05).The monomeric peptide group significantly increased the serum IgM content(P<0.05),and the tandem peptide group had a tendency to increase the IgM content of the lamb serum(P>0.05).4.The expressions of TLR2 and TLR4 genes were significantly down-regulated in both monomeric and tandem peptide groups(P<0.05).Monopeptide group and tandem peptide group significantly down-regulated IL-6 gene,IL-2 gene,IFN-? gene and TNF-? gene expression(P<0.05).5.Intestinal flora of lamb is mainly composed of thick wall bacteria,Bacteroides,proteobacteria and actinomycetes.At 14 d and 21 d,the tandem peptides and monomeric peptides were significantly higher than those of the blank group at the time of Bacteroides Bacteriology(P<0.05).At the 35 th day,the concentration of tandem peptide and monomeric peptide was significantly higher than that of the blank group(P<0.05).At 35 days after actinomyces,the monomeric peptide group was significantly lower than the blank group(P<0.05).The proteobacterial phylum Proteobacteria had a tendency to be higher than the blank group at the 14 th day(P>0.05),and the tandem peptide group was significantly higher than the blank group at the 21 st day(P<0.05).The results showed that: Antibacterial peptide CC31 has the function of promoting the development of intestinal epithelial cells and improving the morphological structure of intestinal tissues;Antibacterial peptide CC31 can upregulate the expression of the intestinal epithelial tight junction protein gene and protect the intestinal mucosal barrier function;Antibacterial peptide CC31 can increase the serum Ig A,IgG and Ig M levels in lambs and contribute to the construction of the lamb's immune system;Antimicrobial peptide CC31 can down-regulate the expression of TLR2 and TLR4 genes and the expression levels of pro-inflammatory cytokines IL-2,IL-6,TNF-? and IFN-? in lambs,and can reduce the inflammatory response induced by weaning stress in lambs,and help build the lamb's immune system;Antimicrobial peptide CC31 has a certain influence on the structure of intestinal cryptocyst of lamb,and it can increase the abundance and diversity of intestinal microflora,and it can also increase the colonization of beneficial bacteria and reduce the harmful bacteria content.Conclusion: The antibacterial peptide CC31 monomer peptide and tandem peptide can reduce the effect of weaning stress on lambs,ensure the healthy development of the intestinal tract of the lambs,promote the establishment of immune system,and improve the intestinal flora.Compared to tandem peptides,monomeric peptides have better monomeric peptides than tandem peptides.