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1、DietaryvitaminAcanimprove immunefunction inheat-stressedbroilersReporter:WangSiyuTheoriginalauthor:Z.Y.NiuContentsIntroductionMaterialsAndMethodsResultsAndDiscussionConclusionsIntroductionHeatstress(HS)iscausingincreasingconcerninpoultryaffectFeedefficiency,grow
2、thrate,Mortality,etcvitaminAhasimmunefunctionstobroilerssolveIntroduction-HSIthasbeenestablishedthathighenvironmentaltemperaturesaffectthedevelopmentofaspecificimmuneresponseinchickens(Thaxtonetal.,1968;SubbaRaoandGlick,1970;ThaxtonandSiegel,1972).Whenchickswere
3、exposedtotemperaturesrangingfrom32.2Cto43Cforshortintermittentperiodsofconstanthightemperaturesorcyclinghightemperatureconditions,theresultingantibodyresponsetosheepredbloodcells(SRBC)wasreducedsignificantly.Introduction-VitaminAVitaminAhaslongbeenknownforitsrol
4、einimmunity.thereisevidencefromotherstudiesinanimalsandhumansthatadministrationofvitaminAaffectsbothspecificandnon-specificarmsoftheimmunesystemMaterialsAndMethodsThedesignusedwasa3*2factorrandomizedblockdesign.Atotalof1801-day-oldArborAcressmalebroilerchickswer
5、erandomlyassignedtosixgroups,eachgrouphadsixreplicates,andeachreplicatecontainedfivebirds.Before3weeksofage,thebirdsofeachtwogroupswerefedacorn–soybeanmealbasaldiet,supplementedwithvitaminA(retinol)ataconcentrationof750(low),1500(standard;NationalResearchCouncil
6、,1994)and15000(high)IU/kgMaterialsAndMethodsAfter3weeksofage,thebirdsofeachtwogroupsfedthesamedietarytreatment,wererandomlydividedintothetwoenvironmentalchambers.Inonechamber,theambienttemperaturewasadjustedsothatdailyfluctuationswerebetween24.8℃and38.8℃,simulat
7、ingdiurnaltemperatureduringHS.Intheotherchamber,environmentaltemperaturewaskeptataconstant24.8C(thermoneutral,TN).MaterialsAndMethodsOnday32(12daysaftertransfer)sixbirdspertreatment,fromeachenvironmentalchamber,wererandomlyselectedandweighed.Theabdominalareawasc
8、leanedwithalcoholanda3%suspensionofpreswollenSephadexG-50preparedin0.85%sterilesalinewasinjectedintotheabdominalcavityat1ml/100gBW.MaterialsAndMethodsHarvestingabdomi
