Prediction of the Ym factor for livestock from on-farm accessible data

JAURENA, G.; CANTET, J.M.; ARROQUY, J.I.; PALLADINO, A.; WAWRZCKIEWICS, M.; COLOMBATTO, D.

LIVESTOCK SCIENCE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 177 p. 52 - 62

1871-1413

Methaneemissionfactor(Ym)isdirectlyinvolvedtocalculatetheworldwidelivestockmethaneinventories,henceitisimportanttorefinetheestimationofthisparameterfordifferentlivestockproductionsystems.ThepurposeofthisworkwastogeneraterefinedmathematicalmodelstopredictCH4 emissionsfromanextensivecompilateddatabaseaton-farmlevelandtocomparethemwithdifferentmodelsalreadyavailableintheliterature.Methaneemissionpredictivemodels(expressedasYm,%grossenergyintake;andmethaneproduction, CH4p, g an1 d1) wherefittedtakenintoaccounttheproductionsystem,thelivestocktypeandthefeedcharacteristicsavailableaton-farmlevelwithinareasonableuncertaintyrange.Inordertodevelopthemodels,onlyeasyavailableparameterswereselectedtofitnewmathematicalmodels.Hence,thefullmodelincluded:ruminanttypes(beefcattle,dairycattle,andsheep),fibresources(freshforage,conservedforage,andstraw)andconcentratelevels(DMbasis)inthediet(Low, o35%;Intermediate,35?65%;High, 465%).FullmodelswereassessedbytheBayesianInformationCriterion(BIC)andtermsthatdidnotreachsignificancelevel(Pr0.05)weredroppedfromthemodel.Furthermore,predictedresultswereassessedthroughcorrelationandregressionanalysesconsideringthemodelsignificance.Modelsdevelopedinthisstudywerecomparedbythedegreeofadjustmentofasimpleregression.AdditiveandtechniquetermswereinitiallydroppedfromthefullmodelusedtopredictYmbecausetheydidnothaveeffectintheprediction(P40.10).Therefore,thefinalequationforModel1was:Ym(a)¼Inter-cept0.243(70.051)DMI(kgd1)þ5.9103(71.17103)NDF(gkg1 DM1)þ5.7103(71.63103)DMD(gkg1 MS1) (BIC¼559).Alltermsofthismodel,interceptfactor(typeofcattlesourceoffibrelevelofconcentrate),DMI,NDF,andDMDweresignificant(Po0.0001).DMIwasthetermwiththegreatestweightinthemodel.ThepredictedYmvaluedecreasedabout0.243percentageunits(Po0.0001)pereachadditionalkginDMI.Whentheequationwascomparedwithpreviouspublicatedmodels,ourmodelshowedasatisfactorydegreeoffitting.In conclusion,thisnewmodelimprovedtheestimationoftheYmfactorfrombeefanddairyproductionsystems,usingdifferentforagequalitycharacteristicsfromon-farmlevel to increaseprecision