Effect Of Dietary Chitosan Oligosaccharides On Lleal Mucosal Immunity In Broilers

The using of antibiotics as feed additive was banned by the European Union in 2006 due to its serious abuse and residue problem in the domestic animals.Natural,nontoxic feed additives are benefit for reducing the overuse of antibiotics and can improve the meat quality.The aim of this study is to investigate the effect of chitosan oligosaccharides(COS)on ileal mucosal immunity in broilers,to confirm the appropriate supplemented dose in diet,and to provide theoretical basis for the application of COS in poultry production.In this study,one hundred and sixty one-day-old healthy AA broilers were randomly divided into four groups with eight replicates per group for 42 days,that is,control group,COS Ⅰ,COS Ⅱ and COS Ⅲ group.The control group was fed with basal diet,a typical corn-soybean diet,COS was mixed into the basal diet to constitute the diets with 200 mg/kg,350 mg/kg and 500 mg/kg of COS forCOS Ⅰ,COS Ⅱ and COS Ⅲ groups,respectively.This study investigated the effects of COS on ileal mucosal immunity in broilers by histopathology,biochemistry,flow cytometry and quantitative real-time PCR(qRT-PCR)methods.The results are as follows:(a)The structural of villus were integrity,no obvious pathological change was found.When compared with control group,the villus height and villus height/crypt depth ratio were significant increased,(b)The results of flow cytometry showed that compared with the control group,the percentages of CD3+CD4+ T cells and CD4+/CD8+ratio were increased,(c)Real-time PCR analysis shown that the levels of IgA,IgM and IgG mRNA expression in the COS Ⅱ and COS Ⅲ group were significant higher than control group as well as IgA in the COS Ⅰ group increased.(d)The levels of IL-1β,IL-2,IL-4,IL-6,IFN-γ and TNF-α mRNA expression in the COS II and COS III group at 21 and 42 days and IL-6 in the COS I group at 21 days were increased.(e)The S phase lymphocytes and PI were increased in the COS II and COS III group while G0/G1 phase lymphocytes were decreased.(f)No significant changes of apoptotic lymphocytes was observed.(g)The GSH-px,SOD,GSH,T-AOC and IHR in the COS II and COS III group were significant increased while MDA was decreased at 21 and 42 days of age when compared with control group,the T-AOC in the COS I group significantly increased at 21 days of age.(h)Comparison among COS supplement groups,those above-mentioned parameters of the COS II and COS III group showed greater change than those of the COS I group.In conclusion,diet supplement 350 and 500 mg/kg COS could improve ileal mucosal immunity via several aspects including cellular immunity humoral immunity.350 mg/kg of COS was an optimal supplemented level in this study.