Nutritive value of leaves from tropical trees and shrubs: 1. In vitro gas production and in sacco rumen degradability

摘要

Leavesfromtwelvedifferenttreesandthreeagriculturalcrops,commonlyavailableinthetropicswereselected,driedandsubjectedtoanalysisbytheinsacconylonbagdegradabilitytest,theinvitrogasproductiontestandtheKjeldahltestfornitrogen.Theproteincontentoftheleaveswasnegativelyrelatedwiththeproportionofleavesintheharvestedfreshfoliage(r=-0.63).Therelativerankingofthefeedswassimilarwhenevaluatedbytheinvitroandinsaccomethodsafter24or48hincubation,andwasinlinewithpracticalobservationsontherelativevalueofthesefeedsforgoats.Theexceptionwasthesugarcanebagasse(pressedcanestalkafterextractionof2/3thejuiceinanartisancrusher)whichhadahighergasproductionthanthebestofthetreeleaves(Cassava,gliricidiaandI.teysamii)butalowerinsaccodegradability.Asimilarsituationprevailedinthecaseofthesugarcaneleaveswhichwereratedrelativelyhigherbytheinvitrogastesttnantheinsaccodegradabilitymethod.Therankingofthefeedsusingthesumofthecoefficientsquot;aquot;+quot;bquot;(thetotalpotentialdegradability)derivedfromtheequationp=a+b(1-e-ct)intheinsaccorumendegradabilitytestwasbroadlysimilar(r=0.56)totherankingbythe24hdrymatterloss.Thequot;cquot;coefficientwasnotrelated(r=0.16)tothe24hdrymatterlossnortothepracticalassessmentofthenutritivevalueofthefeeds.Itisconcludedthattheinvitrogasproductionandinsaccorumendegradabilitytechniquesareequallyusefulforpredictingthepotentialnutritivevalueoftropicaltreeleavesbutthattheinvitrogasmethodgiveserroneousresultsforcropresiduescontainingmoderatelevelsofsolublesugars.