| The early stage of hatching is the critical period for the survival of chicks,because the immune function of chicks is not perfect and is vulnerable to external pathogens,so it is of great significance for poultry industry to improve the early immune protection of chicks.When probiotics and some Chinese herbal medicines enter the intestinal tract,they can regulate the microecological balance of intestinal flora,promote intestinal development,stimulate the lymphoid tissue on the intestinal mucosa,and activate the systemic immune system by relying on lymphocyte recycling,so as to improve the systemic immune function.The early development and maturation of intestinal tract can provide guarantee for the growth,development and production performance of laying hens.However,at present,there are few studies in ovo injection on the early nutritional regulation of layer chicks.By means of in ovo injection technology,the purpose of this study was to explore the effect of astragalus synbiotics fermented by probiotics on early growth and development,systemic immune function and intestinal mucosal immune function of laying chicks,so as to verify its practical application effect.The study provided a theoretical basis for improving the immune function and preventing early diseases of layer chicks.600 eggs with fertile embryos were divided into four treatment groups.For every treatment,five replicates were used while thirty eggs were used per replicate.The four treatment groups were as follows:Non-injected group,0.2 m L/egg 0.9%buffer saline injection group(saline group),2×10~6 cfu/egg lactic acid bacteria injection group(probiotic group)and 2 mg/egg fermented astragalus injection group(synbiotic group).The above solution of intra-amniotic injection was carried out on 18.5 days of embryonic age.After shelling,the hatching performance of each group was analyzed.A total of 75 female layer hatching chicks were selected from each treatment group and randomly assigned to five repeated cages with 15 chicks in each cage.The growth performance and immune organ index on 1,7,14 and 21 days post-hatch of chicks were evaluated,respectively.The proliferation function of blood lymphocytes was detected by MTT proliferation method.The concentrations of serum cytokines(IL-2 and IFN-γ)and intestinal lavage fluid SIg A was detected by ELISA method.The morphological changes of intestinal tract were observed by HE staining.The number and distribution of Ig A~+cells were observed by SP immunohistochemical method.The relative expression of ileum cytokines(IL-2,IL-6,IFN-γ,TLR-4)and the relative abundance of cecal microflora were observed by fluorescence quantitative PCR.The results are as follows:1.In terms of growth and development,compared with the two control groups,in ovo injection of lactic acid bacteria or fermented astragalus synbiotics did not affect the hatching performance of layer chicks,but significantly increased the feed intake(FI)and body weight gain(BWG),and decreased the weight ratio(P<0.05).In ovo injection of fermented astragalus synbiotics significantly affected the BWG and weight ratio of 15-21 days,and it had a significant effect on the immune organ index on 14 days(P<0.05),and significantly increased the thymus index on 7 days and the spleen index on 21 days(P<0.05).2.In terms of system immune function,in ovo injection of lactic acid bacteria or fermented astragalus synbiotics could significantly promote the proliferation of peripheral blood lymphocytes and increased the concentrations of cytokines IL-2 and IFN-γin serum of layer chicks on 7 and 14 days(P<0.05).And compared with the other three groups,in ovo injection of fermented astragalus synbiotics had more significant effect on the proliferation of peripheral blood lymphocytes and the concentrations of serum cytokines.3.In terms of intestinal development and mucosal immunity,compared with the two control groups and lactic acid bacteria group,in ovo injection of fermented astragalus synbiotics significantly increased the VH in duodenum and jejunum,decreased the CD and increased the VH/CD ratio in layer chicks after 7 days(P<0.05),and increased the number and distribution of Ig A~+cells in intestinal villi of duodenum and jejunum,and significantly promoted the secretion of SIg A in intestinal lavage fluid after 7 days(P<0.05).The expression of cytokines IL-2,IFN-γand TLR-4 increased and IL-6 decreased in ileum,and indicated fermented astragalus synbiotics may regulate the relative balance of Th1/Th2 cells.The relative abundance of Lactobacillus and Bifidobacterium in cecal microflora increased,and the relative abundance of Escherichia coli decreased.In summary,under the experimental conditions,in ovo injection of lactic acid bacteria and fermented astragalus synbiotics could promote the growth and development and regulate intestinal mucosal immune response of layer chicks.And the beneficial effect of fermented astragalus synbiotics was better than that of lactic acid bacteria.It plays an important role in improving the growth and development of layer chicks,promoting intestinal health,and regulating the ability of layer chicks to defend against external pathogens under normal conditions. |
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