In vitro rumen fermentation kinetics and nutritional evaluation of olive tree (Olea europaea L.) pruning residues as affected by cutting regimen

摘要

Nutritivevaluesofthebranches(stemswithleaves)fromOleaeuropaeatreescutat25,50,75or100cmdistancefromthetip(cuttinglength)wereevaluatedbydeterminationofthemicrobialnitrogen(MN)andbiomass(MBM)productionafterincubationwithrumenfluidand15N-tracerfor96hintheabsenceorpresenceofpolyethyleneglycol(PEG,6000).Thecharacteristicsoffermentation(initialgasproducedfromsolublefraction;a,gasproductionduringincubationwhichproducedfrominsolublebutfermentablefraction;b,potentialgasproduction;a+b,fractionalrateofgasproductionperhour;c)wereassessedusinganinvitroincubationtechniquewithrumenfluid.Effectivedegradability(ED),partitioningfactor(PF)andshortchainfattyaids(SCFA)werealsoestimatedintheexperimentalolivepruningbranches.Therewasanegativeeffectofcuttinglengthonallthestudiednutritiveparametersandfermentationcharacteristics.ThevaluesofMN,MBM,ED,PF,SCFA,a+bandcdeclinedwiththeincreaseincuttinglength.Theolivebranchescutat25or50cmdistancefromthetipproducedhigher(P0.05)amountsofMN(0.53mg/gDM)thanthosecutat75and100cmlengths(0.30mg/gDM).ThevaluesofED,SCFAandPF,andtheratiosofMNorMBMtoeffectivedegradedsubstrateweresignificantlyhigher(P0.05)inthecuttingolivebranchesat25cmlengthcomparedtoothercuttinglengths.TherewasapositivecorrelationbetweenMNorMBMproductionandSCFA,PF,EDanda+bvalues.Thegreatestproportionofgasproductionoccurredduringthefirst48hofincubation.MicrobialNandMBMproductionwerepositivelycorrelatedwitha+b,SCFA,PFandED.TheadditionofPEGtotheplantsamplesincubatedwithrumenfluidataratioof2:1PEG:substrateincreasedthevaluesofgasproduction,characteristicsoffermentation,MN,MBM,SCFAandED.TheresponseoftheolivepruningbranchestoPEGtreatmentintermsofincreasedgasproductionvariedbetweencuttinglengthsandtendedtodeclineasincubationprogressed,withthehighestincrease(17%)duringthefirst24hofincubation.Onthebasisofthestudiesonnutritiveparameters,olivepruningbranchescutat25cmdistancefromthetipindiameter3mmwerenutritionallywell-suitedasdietarysupplementsforruminants.