Study On The Effect And Mechanism Of Dietary Supplementation Of Antimicrobial Peptides And Synbiotics On Growth In The Broiler

Nowdays, there have been 70 years since the antibiotics used as growth promoters in livestock and poultry in the world. China is aslo a big coutry of using of antibiotics in livestock and poultry. Since the using of antibiotics in all over the world, a series of problems such as environmental pollution, drug residuces, resistant bacterial strains have emerged. To research and develop biological feed additives instead of antibiotics becoming the future development trend in China’s feed additives. Antibacterial peptides, probiotics and prebiotics all have different degree of function of promoting growth, improving the intestinal micro ecological environment and improving the level of immunity. They were thought to be the best replacement of antibiotics.This study was carry out to investigate the effect of dietary supplementation with the cecropins which was already been applicated and promoted in the market lonely or combined with synbiotics maded in the laboratory by ourself on the improvement of growth and metabolism, intestinal health and immunity in broilers. The cecropin was buyed from Zhongnong Ying Tai Group, The symbiotic was consist of Lactobacillus plantarum, Bacillus subtilis, Saccharomyces cerevisiae and chitosan oligosaccharide with the proportion of1:1:1:1. Carrying the feeding experiment, to explore whether both of them have a synergistic action by detecting the indexes of the growth performance indexes, blood biochemical indexes, intestinal microflora, immune organ index, immunological activity cells in small intestinal mucosa, intestinal mucosa morphology and structure and the m RNA expression levels of toll-like receptors and β-defensin. Try to provide a theoretical basis for the development of an new feeding additive with the function of regulating the immunity. The results showed:(1) The average final weight and the average daily gain were significantly increased(P<0.05), the feed/gain was significantly decreased(P<0.05) with the supplementation of antimicrobial peptides, synbiotics or both of them.(2) The serum total protein, albumin, and Ig A levels at day 21 and the serum albumin level at day 42 were significantly increased(P<0.05), the serum triglyceride level and the activity of aspartate transaminase at day 42 was significantly decreased(P<0.05)with thesupplementation of 0.5% antimicrobial peptides. The serum Ig G level and the activity of glutathione peroxidase at day 21 was significantly increased(P<0.05), The serum triglyceride level and the activity of aspartate transaminase at day 21 was significantly decreased(P<0.05),the activity of alanine aminotransferase at day 21 was extremely significantly decreased(P<0.01) with the supplementation of synbiotics. The serum total protein, albumin, Ig A levels at day 21 and the serum total protein, albumin, Ig G, Ig A and Ig M levels at day 42 were significantly increased(P<0.05), the activity of glutathione peroxidase at day 42 were significantly increased(P<0.05), the activity of glutathione peroxidase at day 21 were extremely significantly increased(P<0.01), the serum blood urine nitrogen, total cholesterol and triglyceride levels at day 21 and at day 42 were significantly decreased(P<0.05), the activity of alanine aminotransferase and aspartate transaminase at day 42 were significantly decreased(P<0.05), the activity of aspartate transaminase at day 21 was extremely significantly decreased(P<0.01) with the supplementation of antimicrobial peptides and synbiotics.(3) The number of Escherichia coli and Salmonella were decreased(P<0.05, P<0.01)and the number of Lactobacillus was increased(P<0.05, P<0.01) in duodenum, jejunum,ileum and caecum in AA broilers with the supplementation of antimicrobial peptides,synbiotics or both of them.(4) The number The thymus index in AA broilers was significantly increased(P<0.05)with the supplementation of antimicrobial peptides, synbiotics or both of them.(5) The number of the intraepithelial lymphocyte in ileum mucosa was significantly increased(P<0.05) in 21-old-day AA broilers with the supplementation of 0.5% antimicrobial peptides. The number of the intraepithelial lymphocyte and the goblet cell in duodenum mucosa was extremely significantly increased(P<0.01) in 21-old-day AA broilers with the supplementation of 0.3% synbiotics. The number of the intraepithelial lymphocyte in duodenum, jejunum and ileum mucosa,the goblet cell in duodenal and ileum mucosa was extremely significantly increased(P<0.01) in 21-old-day AA broilers, the mast cell in jejunum mucosa was significantly increased(P<0.05) in 21-old-day AA broilers with the supplementation of antimicrobial peptides and synbiotics.(6) The villus height/crypt depth ratio in duodenum and jejunum were significantly increased(P<0.05); the mucosal thickness in jejunum was significantly increased(P<0.05);the villus width in jejunum was significantly decreased(P<0.05); The villus height/crypt depth ratio in ileum was extremely significantly increased(P<0.01); the crypt depth in jejunum and ileum were extremely significantly decreased(P<0.01) in 21-old-day AA broilers with the supplementation of 0.5% antimicrobial peptides. The villus height/crypt depth ratio in duodenum; the villus height/crypt depth ratio in ileum; the mucosal thickness in jejunum were significantly increased(P<0.05); the crypt depth in duodenum and ileum were significantly decreased(P<0.05); the villus height/crypt depth ratio in jejunum was extremely significantly increased(P<0.01); the villus width in duodenum, the crypt depth and villus width in jejunum was extremely significantly decreased(P<0.01) in 21-old-day AA broilers with the supplementation of synbiotics. The villus height/crypt depth ratio in duodenum and ileum were significantly increased(P<0.05); the villus height and mucosal thickness in duodenum,the mucosal thickness in jejunum, the villus height and mucosal thickness in ileum were extremely significantly increased(P<0.01); the villus width in jejunum and ileum were extremely significantly decreased(P<0.01) in 21-old-day AA broilers with the supplementation of antimicrobial peptides and synbiotics.(7) The m RAN expression levels of beta-defensin-6, TRL2 and TRL4 in liver and spleen and the m RAN expression levels of beta-defensin-6 and TRL4 in kidney were significantly increased(P<0.05, P<0.01) in 21-old-day AA broilers with the supplementation of antimicrobial peptides, synbiotics or both of them.