Influence of fibrolytic enzymes on in vitro methane production and rumen fermentation of a substrate containing 60 % of grass hay

摘要

Batchculturesofmixedrumenmicroorganismswereusedtostudytheeffectsofexogenousfibrolyticenzymesontheinvitrofermentationofasubstratecomposedbya60:40mixtureofgrasshayandconcentrate.Threeenzymaticpreparationsweretested:cellulasefromAspergillusniger(CEL),xylanasefromTrichodermaviride(XYL),anda1:1mixturecellulase:xylanase(MIX).Samplesofsubstrate(500mgdrymatter(DM))wereaccuratelyweighedinto120-mlserumbottlesandenzymeswereaddeddirectlyintothebottlesatthreelevels:0(control;CON),15(-15)and30(-30)IU/gDMsubstrate.Bottleswerekeptatroomtemperaturefor24hbeforeincubationwithbufferedrumenfluid.nbsp;Allenzymatictreatments,withtheexceptionofCEL-15,increased(P0.05)CH4productionafter6hofincubation,butafter24hofincubationdifferences(P0.05)withcontrolwereonlydetectedforXIL-15,XIL-30andMIX-30.Acetate,propionateandbutyrateproductionsatboth6and24hofincubationwereincreased(P0.05)byallenzymatictreatments.NH3-Nconcentrations,pHandgasproductionat24hofincubationwerenotaffected(P0.05)bytheadditionofenzymes.ThetreatmentofsubstratewithXIL-15,MIX-15andMIX-30increased(P0.05)neutral-detergentfibredegradability(61.3,59.9and60.6%,respectively)comparedtothecontrol(56.5%).nbsp;Theresultsindicatethatthexylanasewasmoreeffectivethanthecellulaseinstimulatingtheinvitrofermentationofsubstrate,butformostofthemeasuredparameterstherewerenodifferences(P0.05)duetothelevelofenzymes(15vs.30IU/gDM).