Effect of variety and wilting on HCN content of cassava leaves and on intake, digestibility and N retention by growing pig

摘要

Twoexperimentswerecarriedouttostudytheeffectofdurationofwilting(0,24or48h)onHCNcontentofleavesfromquot;sweetquot;andquot;bitterquot;varietiesofcassavaandontheirnutritivevalueforpigsasmeasuredbydigestibilityandNbalance.Inthefirstexperiment,thedurationofwiltingwas0,24or48h.Inthesecondexperiment,theleavesfromthebitterandsweetvarietieswerefedtopigs,eitherfreshorafter24hwilting,astheonlysupplementarysourceofproteinindietsbasedinbrokenriceandsugarpalmjuice.ThebittervarietywashigherinDM,NandHCNthanthesweetvariety.However,thereweresignificantinteractionsbetweenvarietyandtimeofwilting.DMincreasedandHCNdecreasedatafasterrateinthebitterthaninthesweetvariety.Wiltingcassavaleavesforupto48hreducedHCNcontenttominimalvalues,therateofdecreasebeingmorepronouncedinthebitterthaninthesweetvariety,withnodifferencesbetweenvarietiesafter48h.Therewerenodifferencesinthenutritivevalueforpigs,betweenbitterandsweetvarieties,norweretherebenefitsfromwiltingfor24hours,asmeasuredbyapparentdigestibilitiesofDM,crudeproteinandcrudefibre,andbyNretention.Thefreshcassavaleavesprovidedabout20%ofthedietDM,whichresultedinHCNintakesoffrom3.08to3.19mg/kgLWforthedietswithfreshcassavaleaves,andfrom1.85to2.16whentheleaveswerewilted24h.Itisconcludedthataminoacidimbalance,levelsofcellwallconstituentsandcondensedtanninsaremoreimportantthanHCNlevelsinlimitingtheusefulnessofcassavaleavesforpigs.