General Anatomy of the Ruminant Digestive System

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Title:
General Anatomy of the Ruminant Digestive System
Physical Description:
Fact sheet
Creator:
Umphrey, J.E.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

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Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"September, 1992"
General Note:
"DS 31"

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Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
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IR00004705:00001


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GeneralAnatomyoftheRuminantDigestiveSystem1 TheInstituteofFoodandAgriculturalSciencesisanEqualOpportunity/AffirmativeActionEmployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,ornationalorigin. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/JohnT.Woeste,DeanJ.E.UmphreyandC.R.Staples2Thedairycowisamagnificentproduceroffood. Inapproximately10months,agoodcowcanproduce 496poundsofprotein,784poundsofenergyinthe formofthesugarlactose,560poundsoffat,and112 poundsofmineralsallin16,000poundsofmilk.This isenoughproteintosupplytheneedsofamanfor nearly10years,enoughenergyfor5years,and enoughcalciumfor30years. Thesupplyofhighqualityfeedstuffstothecow's highlycomplexdigestivesystemhelpsaccomplishthis wonderfulfeat.Anunderstandingofthisdigestive systemisamustformakingintelligentfeeding decisions.STARTINGTHEDIGESTIVEPROCESSChewingisthefirststepinprocessingthefeed. Thisisnosmalltaskasthecowmakes40,000to 60,000jawmovementsperdayasitchewsand rechewsregurgitatedfeed.Thenitpassesdowna2 1/2to3foottubecalledtheesophagusintoalarge fermentationvatof40to50galloncapacity.Here digestionoffeedgoesonby500,000billionbacteria and50billionprotozoalivingandmultiplyingthere. Thesesmallorganismshaveseveralunique characteristicswhichallowthecowtothrivein situationswhichwouldbeimpossibleforother animalstolive.Theydigestfiberfoundinhay,silage, andpastureforenergy,makeproteinfromnitrogen, andsynthesizeBvitaminsfortheirhost,thecow.FORESTOMACH(RETICULORUMEN)Thisfermentationvatiscomposedoftwoareas calledthereticulumandtherumen.Thereticulum hasadistinctive"honeycomb"appearance.Itaidsto helpbringbolusesoffeedbackuptothemouthfor rechewing.Italsoservesasareceptacleforheavy foreignobjectsthatsheeats.Aconditionknownas "HardwareDisease"mayoccurifametalobjectsuch aswireoranailisswallowedandpuncturesthe reticulumwall.Thisconditionmayprovelethalfor tworeasons.First,thebacteriaandprotozoacan contaminatethebodycavityresultinginperitonitis andsecond,theheartanddiaphragmmaybe puncturedbytheobjectcausingfailureofthese tissues. Therumenis,byfar,thelargestcompartment. Itspurposeistostorelargequantitiesoffeed,keep thefeedmixingbystrongcontractions,andtoprovide asuitableenvironmentforthebacteriaandprotozoa tolive.Thisenvironmentiskeptagreeabletothe microorganismsbymaintainingarelativelyconstant temperatureandpHandbyremovingmanyoftheir wasteproducts.Mostofthewasteproductsare volatilefattyacids.Thesevolatilefattyacidsarethe primarysourcesofenergyforthecow.Theyare absorbedbythousandsof"finger-like"projections liningthebottomandsidesoftherumenwall.These canbe1/2inchlongandtheyincreasethesurface areaoftherumensoastoincreaseherabilityto absorbvolatilefattyacids. 1.ThisdocumentisFactSheetDS31oftheDairyProductionGuide,publishedSeptember,1992,FloridaCooperativeExtensionService.For moreinformation,contactyourcountyCooperativeExtensionServiceoffice. 2.ExtensionAgentIandAssociateProfessor,respectively,DepartmentofDairyScience,InstituteofFoodandAgriculturalSciences,University ofFlorida,Gainesville.

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GeneralAnatomyofRuminantDigestion Page2OMASUMOncethefeedhasbeenreducedinsizeby chewinganddigestionbythebacteriaandprotozoa, itcanpassintoathirdcompartmentcalledthe omasum.Thisareahasbeennicknamedthe"manyplies"duetoitsuniquestructure.Ithasthe appearanceofanopenbookwiththreesidesbound. Thetissueswithinarelikenedtothepagesofabook andarecalledleaves.Upto100leavescanbefound intheomasum.Theseleaveshavesmallpapillaeon themwhichabsorbalargeportionofthevolatilefatty acidsthatwerenotabsorbedthroughtherumenwall. Waterandelectrolytessuchaspotassiumandsodium arelikelyabsorbedhereaswellthusdryingoutthe feedstuffsbeforetheyenterthenextcompartment.ABOMASUMThisfourthandlastcompartmentwhichmakeup thecow'sstomachistheabomasumor"true"stomach asitiscalledbecauseitfunctionsinaverysimilar waytothestomachofamanorpig.Asinthe omasum,theabomasumcontainsmanyfoldsto increaseitssurfacearea.Theseleavesenablethe abomasumtobeincontactwiththelargeamountsof feedpassingthroughitdaily.Thewallsofthe abomasumsecreteenzymesandhydrochloricacid. ThepHofthedigestacomingintotheabomasumis around6.0butisquicklyloweredtoabout2.5bythe acid.Thiscreatesaproperenvironmentforthe enzymestofunction.Thechiefdigestivefunctionof theabomasumisthepartialbreakdownofproteins. Theenzymepepsinisresponsibleforthis.Proteins fromthefeedandthemicroorganismscomingfrom therumenarebrokendowntosmallerunitscalled peptidesbeforeleaving.SMALLINTESTINEThenextstopinthedigestiveprocessisthesmall intestine,a130foot-long,2inch-widetube.Asthe feedentersthesmallintestine,itmixeswith secretionsfromthepancreasandliverwhichelevate thepHofthedigestafrom2.5tobetween7and8. ThishigherpHisnecessaryforenzymesinthesmall intestinetowork.Inorderforfeedstuffstobecome availabletothecow,theymustbebrokendowninto smallermolecules.Theseenzymesdojustthatby reducinganyremainingproteinstoaminoacids, starchtoglucose,andcomplexfatsintofattyacids. Muchofthatoccursinthesmallintestineusing enzymesandhormonesfromthepancreas,liver,and smallintestine.Absorptionofthesenutrientsalso occurinthelowerhalfofthesmallintestine.The intestinalwallcontainsnumerous"finger-like" projectionscalledvillithatincreasethesurfacearea oftheintestinetoaidintheabsorptionprocess. Muscularcontractionsaidinmixingthedigestaand movingitdowntothenextsection.LARGEINTESTINEThececum,colon,andrectummakeuptherest ofthedigestivetract.Theyarecollectivelyreferred toasthelargeintestine.Itsprimarypurposeisto absorbwaterfromthedigestathusmakingitmore solid.Bacterialivingintheintestineworkat digestinganyfeedstuffswhichescapeddigestion earlier.Usuallythiscontributeslessthan15%ofthe totaldigestion.Betweenthesebacteriaandthose whichpassedoutoftherumen,upto50%ofthedry weightofthefecescanbeofmicrobialorigin.CALFDIGESTIVETRACTDEVELOPMENTThedigestivetractsofcalvesaremorelike humansthancows.Theyhavenofunctioningrumen withbacteriaandprotozoaworkingforher.Ina youngcalf(1monthorless),theabomasumisthe largestcompartmentofthestomach.Itmakesup approximately50to70%ofthetotalstomacharea. Whenthecalfsucklesfromthedamorabottle,the milkbypassesthereticulorumenbygoingthroughthe esophagealgroove.Duringthesucklingprocess, impulsesfromthebrainsendmessagestothe esophagealgroove,causingthesidesofthegrooveto curveupwardformingatube.Thisallowsadirect flowofmilkintotheabomasum.Atthispoint,the enzymerenninissecretedfromthewallsofthe abomasum,causingthemilktocoagulateorcurdle. Thisslowsthepassageofmilkthroughtheabomasum toallowampletimeforthemilktobedigested.As thecalfgetsolderandstartstoconsumegrainand hay,therumenbeginstodevelop.Thisgrowthisdue tothevolatilefattyacidsproducedbythedigestive actionofmicroorganismsintherumen.Thisalso stimulatesthegrowthofthepapillaewhichare developing.Bytheendofthefourthweek,thecalf shouldbeabletoutilizegrainandqualityhaytoa largeextent.Ateightweeksofage,theabomasum comprisesonly30%ofthetotalcapacityofthe stomach,andonly9%whenthestomachreachesfull maturesize.