EAA构成与碳水化合物类型对混合瘤胃微生物体外发酵的影响的中期报告Abstract:TheaimofthepresentstudywastoevaluatetheeffectofdifferenttypesofcarbohydratesandEAAcompositiononinvitrofermentationofmixedrumenmicroorganisms.A2x2x4factorialexperimentwasconductedwithtwotypesofcarbohydrates(starchvsfiber),twolevelsofEAAcomposition(adequatevsdeficient)andfourincubationtimes(4,8,12and24h).Themaindifferenceinfermentationofthetwotypesofcarbohydratesweretheshorterfermentationtimesforfiberthanforstarch.Ingeneral,theEAA-deficientdietresultedindecreasedfermentation,includinglowertotalvolatilefattyacid(VFA)concentration,greaterammonia-Nconcentration,anddecreasedmicrobialproteinproduction.Introduction:Fiberandstarcharethetwomainsourcesofcarbohydratesinruminantdiets,andtheydifferintheirchemicalstructureandfermentationcharacteristics.StarchisareadilyfermentablecarbohydratethatisrapidlybrokendownbyrumenmicrobestoproduceVFAsandmicrobialprotein.Fiber,however,ismoredifficulttofermentandrequiresalongertimetobreakdown.Inaddition,essentialaminoacids(EAA)suchasmethionine,lysine,andhistidineareimportantformicrobialproteinsynthesisintherumen.Materialsandmethods:Therumenfluidwascollectedfromthreeruminallycannulatedsteersfedagrasshay-baseddiet.Thefluidwaspooledimmediatelyandusedasinoculumfortheinvitrofermentation.Twotypesofcarbohydrates(starchandfiber)andtwolevelsofEAAcomposition(adequateanddeficient)weretestedinthepresentstudy.TheEAAcompositionwasbasedontherecommendationsoftheNationalResearchCouncil(NRC)forgrowingbeefcattle.Theexperimentaldesignwasa2x2x4factorialwithfourincubationtimes(4,8,12and24h).TheinvitrofermentationwasconductedintriplicateandthedatawereanalyzedusingtheMIXEDprocedureofSAS.Resultsanddiscussion:Themaineffectofcarbohydratetypeonfermentationwasshownintheshorterfermentationtimesforfiberthanforstarch.At4hofincubation,thefermentationoffiberwasgreaterthanthatofstarch,asindicatedbyhighertotalVFAsconcentration,lowerpH,andhighermicrobialproteinproduction.However,at24hofincubation,thefermentationofstarchwasgreater