effects of supplemental urea sources and feeding frequency on ruminal fermentation, fiber digestion,

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1、AnimalFeedScienceandTechnology171(2012)136–145ContentslistsavailableatSciVerseScienceDirectAnimalFeedScienceandTechnologyjournalhomepage:www.elsevier.com/locate/anifeedsciEffectsofsupplementalureasourcesandfeedingfrequencyonruminalfermentation,fiberdigestion,andnitrogenbalancei

2、nbeefsteersE.G.ab,∗b,cAlvarezAlmora,G.B.Huntington,J.C.BurnsaUniversidadAutónomadeBajaCalifornia,Mexicali,MexicobNorthCarolinaStateUniversity,Raleigh,NC27695-7621,UnitedStatescUSDepartmentofAgriculture,AgriculturalResearchService,UnitedStatesarticleinfoabstractArticlehistory:T

3、heobjectiveoftwoexperimentswastoevaluatenon-proteinNsupplementationwithReceived24June2011protectedureasourcesintermsofrumenfermentationproducts,nutrientdigestibility,andReceivedinrevisedform27October2011Nbalanceinruminallyfistulatedbeefsteers(initialbodyweight239±18kg)fedswitch

4、-Accepted28October2011grass®hay.Experiment1comparedureawithOptigenII,andExperiment2comparedureawith®RumaPro.Inbothexperiments,supplements(400g/kgofdailydietarydrymatter)wereKeywords:fedoncedailyorevery2hinabalanceddesign.Supplementscontainedsoybeanhulls,corngrain,vitamins,andm

5、ineralsaswellasnon-proteinNsources.Non-proteinNNitrogenprovidedUrea0.18g/gofdietaryN.Switchgrasshaywasfedoncedaily,atthesametimeasFiberthesupplementintheonce-dailytreatments.Drymatterintake(4.1kg/dinExperiment1,Digestion4.5kg/dinExperiment2),drymatterdigestibility(P<0.25,0.58±

6、0.014g/ginExperi-Steersment1,0.58±0.010g/ginExperiment2),Nbalance(P<0.83,11.3±1.9g/dinExperiment1,11.8±3.6g/dinExperiment2),ruminalammoniaconcentrations(P<0.29,15.2±1.4mMinExperiment1,11.8±0.6mMinExperiment2),andruminalshort-chainfattyacidcon-centrations(P<0.13,77.7±3.0mMinExp

7、eriment1,75.4±3.0mMinExperiment2)werenotaffectedbyfeedingprotectedureasources.ProvidingasteadysupplyofruminallydegradableNbyfeedingsupplementevery2hvsoncedailydecreasedruminalammo-niaconcentrationsbyapproximatelyone-halfby4hafterfeedinghay(P<0.01inbothexperiments)andincreased(

8、P<0.02inExperiment1,P<0.08)inExperiment2)apparentdigestibilit