| Deoxynivalenol（DON）is a kind of mycotoxin produced by Fusarium graminearum and Fusarium roseum,which major pollute wheat,corn and oats.It is easy to find in food and feed and then make the intestine as the first attacking target with entering the digestive tract.As the first barrier to prevent invasion of pathogens and toxins.Intestinal tract plays an important role in protecting intestinal health of human beings and animals.Laying hens is an important part of the aquaculture industry,annual economic losses caused by mycotoxin contamination need to take into account greatly.Presently,there are few researches about DON single toxicity on laying hens domestic and foreign,the mechanism of DON-induced intestinal damage is still unclear.Therefore,it’s necessary to research the mechanism of intestinal damage induced by DON single toxin in laying hens.Different doses of DON standard were used to research the mechanism of intestinal damage induced by DON in laying hens,the study mainly includes three aspects:clinical toxicity effect,transcriptional and protein level and intestinal microbial metagenomic level.The main contents and conclusions of this paper are as follows:（1）This study was conducted to investigate the effects of DON on performance,egg quality,blood routine examination,serum biochemical parameter and liver oxidation index in laying hens.Results showed that,compared with control,eggshell color,albumen height and Haugh unit value in different DON groups were significantly increased,but the count of WBC and PLT were remarkably decreased（P<0.05 or P<0.01）.In 10 mg·kg-1 DON group,egg production rate was decreased,and HGB,RBC and HCT in blood were significantly increased（P<0.01）.In addition,the supplementation of DON≥10 mg·kg-1,the concentration of UREA and levels of AST,ALT and ALP in serum were significantly elevated,and the activity of T-AOC,GSH-Px and SOD in liver were significantly reduced,but the concentration of NO and MDA in liver were increased（P<0.05 or P<0.01）.However,levels of T-AOC and SOD in 5 mg·kg-1 group were dramatically increased（P<0.05）.In summary,the supplementation of DON under 5 mg·kg-1could affect the blood coagulation function,and the excessive dose can cause the decrease of egg production rate and egg quality,induce organ damage of liver and kidney,and reduce the antioxidant ability of liver in laying hens.（2）This study was conducted to investigate the effects of DON on the intestinal morphology structure,expression of inflammatory cytokines and tight junction proteins in laying hens.On the basis of the experiment in the second chapter,duodenal tissues were collected at the end of the experiment,HE staining was used to observe the intestinal morphological structures.q RT-PCR was used to detect the expression level of IL-1β、IL-6、IL-8,TNF-α,ZO-1,ZO-2 and claudin-1,Western Blot was used to detect the protein expression of ZO-1 and claudin-1 in the intestine.Results showed that intestinal morphology and structure can be damaged by different doses of DON except 1 mg·kg-1 and showed a dose-effect relationship.In 10,20 and50 mg·kg-1 groups,the expression level of IL-1,IL-6 and TNF-αm RNA significantly reduced（P<0.01）,which indicated that DON had an immunosuppressive effect on the body.m RNA levels of tight junctional protein ZO-1,ZO-2 and claudin-1,expression of ZO-1 and claudin-1 also significantly reduced in 10,20 and 50 mg·kg-1 groups（P<0.05 or P<0.01）,which indicated that DON could inhabit the expression of tight junctional protein in the intestine of laying hens.In summary,10,20 and 50mg kg-1DON significantly inhibits the immune function,what’s more,DON could destroy the intestinal barrier function through inhabiting the expression of tight junctional protein,the immune function was affect finally.（3）This study was conducted to investigate the effects of DON on the intestinal microbiota of laying hens analyzed by Illumina-Mi Seq High-Throughput sequencing technology.On the basis of the experiment in the first chapter,at the end of the experiment,fresh fecal were collected to extract DNA,then DNA samples were sent to Shanghai Personal Biotechnology Co.,ltd to make bacterial diversity sequencing analysis.The results showed that,compared with the control,Chao index and ACE index were significantly reduced in all experimental groups（P<0.01）,and the Shannon index were also significantly reduced in 5,10 and 50mg kg-1 groups（P<0.05 or P<0.01）.At Order,Family and Genus levels,compared with control group,the species abundance decreased significantly 1,5 and 10 mg kg-1 groups（P<0.05 or P<0.01）.At the Phylum level,compared with control group,the relative abundances of Bacteroidetes and Proteobacteria were all significantly increased in 10 mg kg-1 group（P<0.05）.At the Genus level,the relative abundances of Lactobacillus,Bacillus,Rhodococcus,Aeriscardovia and Rikenella were all significantly decreased in 10 mg kg-1 group（P<0.05）,the relative abundances of Arcobacter was increased（P<0.05）.In summary,DON reduced the Alpha and Beta diversity of intestinal microbial flora abundance.DON also changed the microbial community structure,10 mg kg-1DON increased the content of pathogenic bacteria and reduced the content of probiotics,which caused the high susceptibility to diseases,reduction of the immunity and the effect of the intestines and the body health. |
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