Effect Of In Ovo Injection Of Astragalus Polysaccharide On The Intestinal Mucosal Immunity Of Chicken

The period immediately following hatch is critical for the survival of chickens,because the immune and digestive systems of the chick are immature at this time,and the maternal antibodies are limited.How to improve the immune function of the body in the early stage of hatching,especially the intestine,is particularly important to resist the invasion of external pathogens.Previous experiments have shown that embryonic egg feeding is an effective and feasible method to provide additional nutrients according to the needs of embryo development during the incubation period to regulate early growth,development and the immune function of chicks.Astraglus polysaccharide(APS)can enhance the body's immunity,anti-oxidation and anti-aging by oral administration or as a feed additive.It also has the functions of promoting intestinal development and improving intestinal mucosal immunity.Therefore,this experiment regulates the early intestinal immunity of broiler chicken by in ovo injection of APS to improve the immune function of chicks in the early stage of shelling,which is important for preventing the occurrence of diseases.To investigate the effect of in ovo injection of APS on the early intestinal mucosal immunity in chicks,240 Arbor Acres broiler(AA+broiler)embryo eggs were randomly divided 4 treatment groups,with each treatment group of three replicates and each replicate of 20 eggs.At the 18.5th d of incubation,II,III,and IV treatment groups were intra-amniotically injected with 0.5 mL APS at concentrations of 2 mg/ml,4 mg/ml,and 8 mg/ml,respectively,and indicated by APS_L,APS_M,and APS_H,respectively.Treatment group I injected with 0.5 mL 0.9%saline at the same site and used as a control group(refered as Control).The hatching rate of each group were calculated on the day of hatching,and the samples were taken on the 1st,7st,14st and 21st days after shelling of age:the weight was obtained;HE staining method was used to observe the changes of intestinal morphological structure;SP immunohistochemical method was used to observe the distribution and quantity of IgA+cells in intestine mucosa.The change of SIgA content in jejunal lotion was detected by ELISA.The expressions of IL-2,IL-6,IFN-?and TLR4 mRNA in intestinal tract were detected by real-time PCR.The results showed that:1.Compared with the control group,the in ovo injection of APS showed no significantly effect on hatching rate,but increased the body weight of the 14 d and21d chick.Among the three groups,the promotion of APSM was the most obvious.2.Compared with the control group,APS could increase the villus height(VH)of the small intestine mucosa of broilers,reduce the depth of crypt(CD),increase the VH/CD ratio and promote the development of intestinal morphological structure to a certain extent.The effects of three concentrations of APS on early intestinal morphological structure were different at different times,intestinal segments and concentrations.Among them,APSM had the most obvious effect on jejunum at 21days.3.Compared with the control group,APS was able to increase IgA cells in the lamina propria of the duodenum and jejunum at 7,14,21 days.However,the promoting effects of duodenum and jejunum were different in different groups at different ages.Among them,the promotion of duodenum was most obvious in the APS_H group at 21 days.4.Compared with the control group,APSM significantly increased the secretion of SIgA antibody at 7d and 21d.5.Compared with the control group,APS up-regulated IL-2 and IFN-?and down-regulated the expression level of IL-6 gene.It indicated that intra-injection of APS could regulate the relative balance of Th1/Th2 cells in the body and up-regulate the expression of TLR4 at different ages.Compared with the control group,APS may up-regulate the expression level of TLR4,and the most significant effect were observed at 7d of APS_L.In summary,intra-amniotic injection of APS could effectively promote the development of intestinal morphological structure,increase the number of IgA+cells in the mucosa and the content of sIgA in intestinal wash,and up-regulate the mRNA expression level of gene IL-2,TLR4,IFN-?and down-regulate IL-6,thereby enhancing the intestinal mucosal function of chicks in the early stage of shelling,and then providing effective and timely immune protection to the body.