Preparation And Preliminary Clinical Application Of Astragalus Polysaccharide Synbiotics

Calf health is the cornerstone of the high-quality development of dairy cattle breeding industry.During lactation,calves face the impact of various diseases,especially calf diarrhea.Due to the incomplete development of the digestive and immune systems of calves,digestive system dysfunction and related diseases are the main causes of calf death.Therefore,improving the intestinal health of calves plays an important role in improving the economic benefits of pastures.The resistance of pathogenic microorganisms to antibiotics poses a serious threat to the health of animals and humans.As the most potential alternative to antibiotics,microecological agents have been widely used in animal clinical breeding as new green and environmentally friendly feed additives.In dairy production,lactic acid bacteria,bacillus,and yeast are commonly used strains of probiotics,while oligosaccharides,polysaccharides,and plant extracts are widely used in probiotics.Synbiotics composed of probiotics and prebiotics can enhance the immune function of ruminants,regulate intestinal microbiota,and prevent and treat diseases.Currently,there are few solid microecological preparations for ruminants,especially calves.The purpose of this experiment is to prepare stable astragalus polysaccharide synbiotics powder using astragalus polysaccharide and bovine lactic acid bacteria,and to clarify the effects of astragalus polysaccharide synbiotics on the immune function,intestinal microbiota,and growth of lactating calves,providing an experimental basis for the development of new microecological preparations suitable for ruminants.In this study,freeze-drying methods was used to prepare astragalus polysaccharide synbiotic powder.The optimized freeze-dried protective agent formulation using response surface methodology in this study was 17.99% skimmed milk powder,7.26% sucrose,8.04% galactooligosaccharides,and 9.64% astragalus polysaccharide,with a residual amount of distilled water;The survival rate of lactic acid bacteria in the prepared bacterial powder was 88.06%.Next,a calf feeding experiment was conducted to evaluate the clinical effect of astragalus polysaccharide synbiotics.Thirty healthy newborn calves of similar age were randomly divided into control group and astragalus polysaccharide synbiotic group,with 15 calves in each group for 28 days.Compared to the control group,the group receiving astragalus polysaccharide synbiotics was supplemented with additional astragalus polysaccharides,in addition to their regular feed.The results showed that:(1)Astragalus polysaccharide synbiotics could significantly increase the average daily gain(ADG)of calves and significantly reduce the fecal score and diarrhea rate.(2)By testing the immunological indexes,astragalus polysaccharide synbiotics can significantly increase the content of Ig A,Ig G,Ig M,IL-2 and IL-10 in serum and significantly reduce the content of IL-6 and TNF-α.(3)Astragalus polysaccharide synbiotics can significantly increase Chao1 index,Sobs index and Shannon index,and significantly reduce the Simpson index.At the gate level,the relative abundance of Cyanobacterium,Firmicutes and Bacteroidota of astragalus polysaccharide synbiotic group increased significantly,while the relative abundance of Proteobacteria decreased significantly.At the generic level,the relative abundance of Escherichia-Shigella and Streptococcus of astragalus polysaccharide synbiotic group decreased significantly.The relative abundance of norank＿f＿＿norank＿o＿＿Clostridia＿UCG-014,Bacteroides and Butyricicoccus increased significantly.The relative abundance of norank＿f＿＿norank＿o＿＿Clostridia＿UCG-014,Bacteroides and Butyricicoccus showed strong correlations with ADG and fecal score.To summarize,this study involved the preparation of astragalus polysaccharide synbiotic powder and demonstrated its effectiveness in promoting intestinal health and growth in calves.