| Animal transportation is a necessary part of poultry farming at home and abroad.Stimuli such as shaking,hunger,lack of water,shock,loading density and temperature changes during transportation cause serious stress to newborn chicks,which brings huge economic losses to poultry farming.The intestinal tract health is very important for newborn chicks in the stage of rapid growth and development,and the intestinal tract dysfunction caused by stress,such as mucosal damage and dysbiosis,will affect the digestion,absorption and immune function of newborn chicks and seriously affect their production performance.In this study,we investigated the basic situation of poultry farming in the Aksu region of Xinjiang,the current situation of transporting newborn chicks,and the mortality of chicks at various time stages due to different distances of transport.To verify the effect of transport stress on the intestinal function of newborn chicks,80 healthy newborn chicks with similar body weight were randomly divided into control group（Control,C0）,transport 2 h group（Transport 2 h,T2）,transport 4 h group（Transport 4 h,T4）,and transport 8 h group（Transport 8 h,T8）to conduct simulated Transport stress test.To further observe the effect of Astragalus polysaccharide on alleviating the intestinal dysfunction of new chicks caused by transport stress,240 new chicks of Hyland White were randomly divided into control group（Control）,transport group（Transport）,transport+water group（T+W）,and Astragalus polysaccharide oral drops group（T+A）,and the new chicks in transport+water and Astragalus polysaccharide oral drops groups were given equal amounts of sterile water and The expression of genes and proteins related to intestinal microbiota,intestinal tight junction protein and ion channel protein were detected to reveal the effect of Astragalus polysaccharide on intestinal dysfunction of neonatal chicks caused by transport stress,and to provide the groundwork for future research into special additives against transport stress.The results showed as follows:（1）According to field research,there are 123 poultry farms in Aksu region,including 4breeder farms,53 egg farms,15 broiler farms,1 national standardized demonstration farm,16autonomous region level demonstration farms and 34 regional level demonstration farms.The transport distance of chicks transferred from 10,000 poultry farms in Aksu region ranged from0 to 500 km.The results of the survey on the mortality of chicks at each time period at different transport distances showed that the mortality of newborn chicks at each time stage increased with the increase of transport distance.（2）Behavioral observations showed that as the simulated transport time increased,the transport group and transport+water group showed mental depression,fainting and mild dehydration,etc.The newborn chicks in the Astragalus polysaccharide oral drops group had good mental status and mobility at 2 h of simulated transport,and as the simulated transport time increased,the degree of mental depression and dehydration was less than that of the newborn chicks in the transport group.（3）The 16S RNA sequencing results showed that the intestinal flora diversity of the cecum contents in the transport stress model group was reduced compared with that in the control group,which indicated that transport could reduce the cecum flora diversity of chicks.Between the transport stress model group and the control group,there were considerable differences in cecum flora function.The abundance of functional flora of microorganisms in several metabolic pathways,including energy production and conversion,nucleotide transport and metabolism,amino acid transport and metabolism,carbohydrate transport and metabolism,biosynthesis of secondary metabolites,inorganic ion transport and metabolism,translocation and catabolism,was reduced in the transport stress model group.Astragalus polysaccharide treatment was able to increase the diversity of the flora,and the community composition structure and abundance of newborn chicks in the astragalus polysaccharide confined group were more similar to those in the control group.The results of functional prediction analysis showed that the functional flora of carbohydrate transport and metabolism,biosynthesis,transport and catabolism of secondary metabolites,signal transduction mechanism,intracellular transport,defense mechanism,secretion and vesicular transport pathways in the cecum after using Astragalus polysaccharide were not significantly different from those in the control group.（4）The histological results of jejunal pathology showed that the jejunal structure of the control group was clear without abnormalities,while the mucosal barrier of newborn chicks was significantly damaged after 4 h of transport stress,with necrosis and detachment of jejunal mucosal epithelial cells,as well as thickening of the mucosal layer;intestinal villi were fragmented in the field of view,and lymphocytes infiltrated in the lamina propria of jejunum and around the intestinal gland.At the same time,the height of the villi in the 2 h,4 h and 8 h transport groups were highly significantly reduced compared with the control group.The histological results of cecum pathology showed that the cecum intestinal villi of newborn chicks in the 8-h transport group were disorganized,and the muscular layer was thickened and congested.Compared with the transport group and transport+water group,the intestinal villi in the astragalus polysaccharide oral drops group were more intact,and the intestinal gland epithelial cells were not significantly detached and structurally intact,indicating that astragalus polysaccharide could counteract the damage to the intestinal physical barrier caused by transport stress.The number of cupped cells in the transport group and transport+water group decreased,indicating that transport stress led to an increase in the number of cupped cells in the jejunum of newborn chicks,and astragalus polysaccharide could alleviate this trend to a certain extent.（5）Transport stress caused a decrease in the gene and protein expression levels of the tight junction proteins Claudin1,Claudin3,Occludin,and ZO-1,and compared with the transport group and transport+water group,Astragalus polysaccharide significantly increased the expression levels of Claudin1,Claudin3,Occludin and ZO-1 genes and proteins,with the most pronounced expression in the 8 h mock transport group.（6）Transport stress resulted in an overall decreasing trend of m RNA expression levels of NKA,Ca2+-ATPase and AQP（AQP1,AQP3,AQP7 and AQP11）related genes,which was alleviated by Astragalus polysaccharide.In conclusion,transport stress reduced the microbial diversity of the chicken cecum,leading to changes in various metabolic pathways,exacerbating the effects of stress on intestinal barrier function and possibly continuing to affect the growth performance of chicks.Astragalus polysaccharide can improve the diversity of flora,maintain the normal community composition structure and flora abundance,improve the function of intestinal flora,and counter the effect of transportation on the gastrointestinal tract.Transport stress causes structural damage to the jejunum and cecum(intestinal villus morphology,mucus barrier disruption,which can be mitigated by Astragalus polysaccharide.Transport stress causes intestinal tight junction protein dysfunction,while Astragalus polysaccharide can significantly improve the function of intestinal barrier in newborn chicks.Transport stress disrupts the function of intestinal ion channels and AQP channels,and Astragalus polysaccharide improves intestinal health and function by regulating intestinal ion channels and AQP channels and balancing ions and solvents in the intestine to counteract the effects of transport on the gastrointestinal tract. |
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