Investigation And Analysis Of Selenium Deficiency Enteritis In Chickens In A City Of Heilongjiang Province

Selenium is one of the essential trace elements for humans and animals.Selenium plays an important role in enhancing immunity,fecundity,growth and development,and disease resistance.Insufficient intake of selenium can lead to the occurrence of many diseases,such as Keshan disease,white muscle disease and so on.In actual production,the lack of selenium in the diet can lead to oxidative stress,energy metabolism imbalance,inflammation,etc.,resulting in damage and dysfunction of various organs.In poultry farming,selenium deficiency can cause damage to the heart,brain,liver,pancreas,muscle and other tissues and organs of chickens,which will seriously affect the production performance of chickens and cause serious economic losses to the poultry farming industry.Therefore,diseases caused by selenium deficiency have been considered as one of the main nutritional and metabolic diseases that endanger the poultry industry.Se-deficiency diseases have obvious regional characteristics,and epidemiological investigation of seleniumdeficiency diseases in chickens in selenium-deficient areas will provide strong evidence for rational prevention and control of the disease.Many studies have shown that selenium deficiency can lead to intestinal barrier damage and diarrhea,which has a greater economic impact on the aquaculture industry.Therefore,exploring the mechanism of selenium deficiency-induced intestinal damage in animals can not only enrich the biological theory of selenium,but also be of great significance for solving practical problems in production.Many areas in Heilongjiang Province belong to severe selenium-deficiency areas,and are also high-incidence areas of chicken selenium-deficiency diseases.This experiment firstly conducted an epidemiological investigation on the selenium-deficiency disease of chickens in a city in Heilongjiang,and on this basis,replicated the selenium-deficient chicken model and preliminarily explored the pathogenesis of selenium-deficiency enteritis in chickens.The experiment selected 601-day-old broiler chickens and randomly divided them into two groups.They were fed normal diet and selenium-deficient diet respectively to establish a selenium-deficient chicken model.After sexual symptoms),they were euthanized,jejunum and duodenum tissues were collected,and histopathology and cell ultrastructure were observed by light microscope and transmission electron microscope.Tissue selenoproteins,inflammatory factors,tight junction proteins,oxidative stress and other related indicators were detected.The result is as follows:(1)survey results show that from 2019 to 2021,the incidence of selenium-deficiency diseases in broilers in a city in Heilongjiang has been high since March,and it is prone to occur in broilers under 38 days of age,accounting for 80% of the total number of selenium-deficient chickens.(2)Histopathological observations showed that the intestinal villi in the jejunum and duodenum of selenium-deficient broilers were incomplete,large number of inflammatory cells were infiltrated,and the crypt structure was abnormal and moved upward;The intestinal microvilli of the jejunum and duodenum are incomplete,the tight junction structure is damaged,and organelles such as mitochondria and ribosomes overflow from the epithelial cells.(3)Selenium deficiency can reduce the levels of 25 selenoproteins in the jejunum and duodenum of broilers.The mRNA expressions of GPX1,GPX2,DIO2,TXNRD3,SEP15,SELPB,SEPX1,SPS2 in jejunum tissue and GPX1,GPX4,DIO1,DIO2,DIO3,SELH,SELW,SEPP1,and SPS2 in duodenum tissue were significantly decreased.(4)the results of oxidative stress index showed that the content of MDA in jejunum and duodenum of selenium deficiency group increased,while the content of GSH and the activities of SOD,GSH-PX and CAT decreased,which indicated that selenium deficiency could lead to oxidative stress in jejunum and duodenum.(5)the expression of β-defensin(AvBD1,AvBD2,AvBD8,AvBD9,AvBD10,AvBD13)mRNA in jejunum and duodenum of selenium deficiency group decreased,indicating that selenium deficiency could decrease intestinal immunity and damage intestinal immune barrier.(6)the expression levels of Claudin1,ZO-1,Occludin and mRNA in jejunum and duodenum of se-deficient chickens were significantly decreased by detecting the expression of tight junction associated proteins and mRNA.The results showed that selenium deficiency could destroy the intestinal mechanical barrier function in jejunum and duodenum of broilers.(7)The detection results of inflammatory factors-related indicators showed that the mRNA and protein expression levels of NF-κB p65,IKKα,IKKβ,IL-1β,IL-6,IFN-γ,and TNF-α were significantly increased in selenium-deficient broilers,and IL The mRNA and protein expression levels of-10 showed a downward trend.Combined with the results of intestinal histopathology,it was shown that selenium deficiency can cause inflammation in the jejunum and duodenum of chickens.To sum up,the occurrence of selenium deficiency diseases in broilers in a city of Heilongjiang Province has certain seasonality,and there are also differences in the incidence of broilers of different ages.Selenium deficiency can lead to oxidative stress due to decreased expression of selenoprotein in jejunum and duodenum,abnormal structure of tight junction,decreased expression of β-defensin(antimicrobial peptide),intestinal barrier damage and inflammation.The results of this study provide theoretical basis and data support for the prevention of selenium-deficient intestinal diseases in broilers.