119

Finishing Pig Nutrition

Meta-analysesDescribingtheVariablesthatInfluencetheBackfat,BellyFat,andJowlFatIodineValueofPorkCarcasses

J. R. Bergstrom, M. D. Tokach, J. L. Nelssen, S. S. Dritz,1 R. D. Goodband, J. M. DeRouchey, and T. A. Houser

SummaryConcernaboutthequalityofporkfathasincreasedintheUnitedStatesoverthelastdecade,largelybecauseoftheincreasedavailabilityanduseofdrieddistillersgrainswithsolubles(DDGS)inswinediets.Theiodinevalue(IV)ofporkfatiscommonlyusedasanindicatorofquality.ToidentifythefactorsassociatedwithcarcassfatIV,meta-analyseswereconductedtodescribetherelevantvariablesandtodeveloppredic-tionequationstoassistswinenutritionistsandproducersinproducingporkfatwithanacceptableIV.Datafrom21experimentswereusedtodeveloppredictionequationsforcarcassfatIVofpigsfedarelativelyconstantdietaryiodinevalueproduct(IVP)throughoutthefeedingperiod,and6experimentswereusedtodeveloppredictionequationsforcarcassfatIVofpigsfedadietaryIVP-reductionstrategybeforemarket-ing.Backfat,bellyfat,andjowlfatIVwereallhighlycorrelatedamongtheexperimentsthatmeasuredtheIVofthemultiplefatdepots(r ≥0.880;P <0.001).Asexpected,thedietaryconcentrationsofunsaturated(primarilypolyunsaturated)fattyacidswerethemostimportantinpredictingcarcassfatIV.However,improvedpredictionmodelswereachievedbyincludingvariablestodescribethepigs’initialandfinalBW,ADG,andcarcassleanness.IncreasedADG,finalBW,BWrangeovercourseofthediet,andbackfatdepthresultedinreducedbackfatIV(P <0.02).BellyfatIVwasalsoreducedwithincreasingfinalBW,BWrangeovercourseofthediet,andbackfatdepth(P <0.03).AreducedjowlfatIVwasassociatedwithanincreaseinbackfatdepthandalowerfat-freeleanindex(FFLI, P <0.02).DataanalyzedtodevelopequationsforpredictingcarcassfatIVusingadietaryIVP-reductionstrategyindicatedthattheconcentrationsofdietarypolyunsaturatedfattyacidsintheinitialdietwerethemostimportant.Theconcentrationsofdietarypolyunsaturatedfattyacidsinthereduced-IVPdietfedbeforemarketingwerealsoimportantinpredictingtheIVofcarcassfat.However,theIVofbackfatwasthemostamenabletochangeusinganIVP-reductionstrategy.FeedingthepigsforalongerperiodandtoaheavierfinalBWresultedinareducedbackfatIV(P ≤0.05).Theseresultsindicatethat,althoughprimarilydeter-minedbydietaryfactors,anunderstandingoftheothervariablesthatinfluencetheIVofporkfatisnecessarytoreducethelikelihoodofconcernswithporkfatquality.

Keywords:fatquality,fattyacids,iodinevalue,predictionequation

IntroductionAttentiontothequalityofporkfathasincreasedintheUnitedStatesoverthelastdecade,largelybecauseofgreateravailabilityanduseofdrieddistillersgrainswithsolubles(DDGS)inswinediets.Feeding10to30%ormoreDDGSmaynotaffect1DepartmentofDiagnosticMedicine/Pathobiology,CollegeofVeterinaryMedicine,KansasStateUniversity.

120

Finishing Pig Nutrition

carcassleancharacteristics,butresultsinanincreaseinunsaturatedcarcassfatandthelikelihoodofsoftbellies(Whitneyetal.,20062).RecenteconomiccircumstanceshaveencouragedporkproducerstofeedgreaterconcentrationsofDDGS,despiteantici-patedreductionsingrowthperformance.Asaresult,someprocessorshavebecomeincreasinglyinvolvedinthefeedingpracticesemployedbyporkproducers.

Iodinevalue(IV)iscurrentlyutilizedasastandardindicatorofcarcass-fatqualityintheUnitedStates.Itprovidesanoverallestimateoftheunsaturatedfattyacidcontent(greaterIV=greaterunsaturatedfattyacidconcentration),anditservesasanindicatorofthefatfirmness(greaterIV=softerfat)andriskforrancidity(greaterIV=increasedriskofrancidity).However,carcass-fatqualitystandardscanvaryconsiderably.VariousthresholdsforbackfatIVhaverangedfrom60(Hugo&Roodt,20073)to74(Boydetal.,19974).Currently,oneU.S.processor(TriumphFoods,St.Joseph,MO)routinelysamplescarcassjowlfatforIVandhasestablishedathresholdof73.However,theIVofporkfatdiffersaccordingtoanatomicallocation,withtheIVofjowlfatgenerallybeinggreaterthanthatofbackfat(Benzetal.,20085).

Therefore,meta-analyseswereconductedtodetermine(1)theeffectsofdietaryfattyacids(ordietaryIVP)andvariablesassociatedwithgrowthandcarcasscharacteristicsonthebackfat,bellyfat,andjowlfatfattyacids(orIV)and(2)theeffectsofdietaryfattyacid(orIVP)-reductionstrategiesonthebackfat,bellyfat,andjowlfatfattyacids(orIV).Thedataforthefirstobjectivewereutilizedtodevelopequationstoimproveourabilitytopredictbackfat,bellyfat,andjowlfatIV.DataforthesecondobjectivewereusedtodevelopequationstoimproveourabilitytouseIVP-reductionstrategiestomeetacceptablefat-qualitystandards.

ProceduresData SelectionThedatausedforthemeta-analyseswereobtainedfromnumeroussources.Acompre-hensivesearchforpublisheddatawasconductedviatheKansasStateUniversity(K-State)Libraries,usingtheInternetandtheISIWebofKnowledge/CABIsearchengine.Additionaldatawereobtainedthroughcommunicationwithauthorsaffili-atedwiththeirstudies.Datafrombothrefereedandnon-refereedpublications,suchastheses,technicalmemos,anduniversitypublications,wereincluded.

Data interpretationTheIVPofeverytreatmentdietwascalculatedas[IVofthedietarylipids]×[percent-agedietarylipid]×0.10,evenwhenalreadyreported,toensureauniforminterpreta-tionofdietaryIVPacrossexperiments.TheIVofthelipidfractionofthedietaryingre-

2Whitney,M.H.,G.C.Shurson,L.J.Johnston,D.M.Wulf,andB.C.Shanks.2006.Growthperfor-manceandcarcasscharacteristicsofgrower-finisherpigsfedhigh-qualitycorndistillersdriedgrainwithsolublesoriginatingfromamodernMidwesternethanolplant.J.Anim.Sci.84:3356-3363.3Hugo,A.,andE.Roodt.2007.Significanceofporcinefatqualityinmeattechnology:areview.FoodRev.Intl.23:175-198.4Boyd,R.D.,M.E.Johnston,K.Scheller,A.A.Sosnicki,andE.R.Wilson.1997.Relationshipbetweendietaryfattyacidprofileandbodyfatcompositioningrowingpigs.PICTechnicalMemo153.PIC,Franklin,KY.5Benz,J.M.2008.Influenceofdietaryingredientsonporkfatquality.Ph.D.dissertation.KansasStateUniversity,Manhattan.

121

Finishing Pig Nutrition

dientswascalculatedwiththeAmericanOilChemists’Society(AOCS1998)equation(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723),usingeitherthepublishedfattyacidvaluesforaddedfatsources(NRC,19986)ortheanalyzedprofilesofthedietordietcompo-nentswhenreported.Whenanalyzedvaluesforthefatorfattyacidcontentwerenotprovidedforcornandsoybean-basedingredients,thefattyacidprofileswerecalculatedbyusingtheNRC(1986)valuesfortheirfatcontentandthefattyacidprofilesfromcornoilandsoybeanoil(Table1).

FortreatmentsappliedovermorethanonedietaryphasetoachieveadesiredIVPordietaryfattyacidtreatment,themeanIVP,meancontentoffattyacids,meanMEdensity,andthemeanpercentageofdietaryMEfromfatofthedietswereusedtodescribethetreatmentapplied.

Theanalyzedfattyacidcompositionofbackfat,bellyfat,andjowlfatwereusedtocalculatetheirIVwiththeAOCS(1998)equation(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723)whentheIVwasnotalreadyreportedusingthisequation.

Overall,21experimentswereusedtodevelopmodelsforpredictingthebackfat,bellyfat,orjowlfatIVofpigsfedarelativelyconstantIVPthroughoutthefeedingperiod.FortheanalysisofIVP-reductionstrategies,6experimentswereusedformodelingthebackfat,bellyfat,orjowlfatIV.

Statistical analysesEachdietaryIVP-treatmentstrategyappliedwithineachstudywasconsideredtheexperimentalunit(orobservation)formodelingtheeffectsofdiet,duration,growth,andcarcassfat/leancharacteristicsonbackfat,bellyfat,andjowlfatIV.Thespecificvariablesofinterestincludedinthedataweretheexperiment,geneticline,gender,dietarytreatmentIVP,grainsource(s),proteinsource(s),addedfatsource(s),aver-agecaloricdensity(ME,kcal/kg),averageC16:0(%),averageC18:0(%),averageC16:1+C18:1(%),averageC18:2(%),averageC18:3(%),dietMEfromfat(%),initialBW(kg),totalduration(d),ADG(kg),endingBW(kg),BWrange(endingBW–initialBW,kg),HCW(kg),backfatdepth(mm),FFLI,andbackfatIV,bellyfatIV,and/orjowlfatIV.

Forthemeta-analysisofIVP-reductionstrategies,thesamedietaryvariablesofinterestwereusedforthedietfedduringtheperiodofreducedIVP.Thetotaldurationofthefeedingperiodwasalsodividedintothenumberofpre-reductionandactualreduc-tiondays.InterimBWwasalsoincludedforthereductionanalysis,andtheBWrangeduringthepre-reductionandactualreductionperiodswereincluded.AnadditionalvariablewascreatedfortheIVP-reductionanalysesbymultiplyingthedietaryIVPfedduringthereductionperiodbythenumberofdaysintheperiod.ThiswasnecessarytodescribethecombinedeffectofthereducedIVPanddurationthatitwasfed.Allothervariablesremainedthesameasthepreviousmeta-analysisofpigsfedaconstantIVP.

6NRC.1998.NutrientRequirementsofSwine.10threv.ed.Natl.Acad.Press,WashingtonD.C.

122

Finishing Pig Nutrition

Thedataforbothmeta-analyseswereanalyzedusingthecorrelation,generallinearmodels,andregressionproceduresoftheSAS(SASInstitute,Inc.,Cary,NC).ThecorrelationprocedurewasusedtoindicatethesignificanceoftherelationshipofeachindependentvariabletothebackfatIV,bellyfatIV,andjowlfatIV,andtoidentifythesignificanceoftherelationshipofIVamongthe3fatdepots.Thegenerallinearmodelsprocedurewasusedtotestthevariablesforsignificantinteractions,andtheregressionprocedurewasusedtodeveloppredictionequationsforbackfat,bellyfat,andjowlfatIVusingastepwiseapproach.Themodelswerefirstdevelopedwithoutusingthedummyvariablesforgender.Intercept-adjustedcollinearitydiagnostics(usingtheSASsyntax=COLLINOINT)andvarianceinflationfactor(SASsyntax=VIF)wereusedtoassistwiththeidentificationofvariableswithcollinearity.Pairwisecollinearityofvariableswasindicatedbyaconditionindexof≥30oravarianceinflationof≥10.When2variableswerefoundtobecollinear,thevariablethatprovidedthegreatestR2waskeptinthemodel,andtheothervariablewasexcluded.Additionally,plotsoftheresidualswereexaminedtoidentifyinfluentialobservations,butnoobservationswereidentifiedandremovedforintroducingbiasintothemodels.Lastly,thedummyvari-ablesweretestedwiththefinalmodelstoevaluatetheinfluenceofgenderonbackfatIV,bellyfatIV,andjowlfatIV.Overall,correlations,interactions,variables,andmodelswereconsideredsignificantatP<0.05.

ResultsMeta-analyses of experiments with treatments consisting of a continuous IVP throughout the feeding period

CorrelationsBackfat,bellyfat,andjowlfatIVwereallhighlycorrelated(r ≥0.887;P <0.0001)toeachother(Table2).Dietarycharacteristicshadthehighestcorrelationswiththecarcassbackfat,bellyfat,andjowlfatIV.ForbackfatIV,thetotaldietaryconcentra-tionofC18:2andC18:3hadthehighestcorrelation(r =0.782;P <0.0001);followedbythedietIVP(r =0.765;P <0.0001),dietaryconcentrationofC18:2(r =0.689;P <0.0001),totaldietaryconcentrationoftheunsaturatedfattyacidsC16:1,C18:1,C18:2,andC18:3(r =0.618;P <0.0001),percentageofthedietMEfromfat(r =0.506;P <0.0001),anddietaryconcentrationofC18:3(r =0.418;P <0.0001).ForbellyfatIV,thedietIVPhadthehighestcorrelation(r =0.882;P <0.0001);followedbythetotaldietaryconcentrationofC18:2andC18:3(r =0.881;P <0.0001),totaldietaryconcentrationoftheunsaturatedfattyacidsC16:1,C18:1,C18:2,andC18:3(r =0.776;P<0.0001),dietaryconcentrationofC18:3(r=0.635;P <0.0001),percent-ageofthedietMEfromfat(r=0.629;P<0.0001),dietaryconcentrationofC18:2(r =0.608;P <0.0001),totaldietaryconcentrationofC16:1andC18:1(r=0.335;P <0.02),andtheMEdensityofthediet(r =0.324;P<0.03).ForjowlfatIV,thedietaryconcentrationofC18:2hadthehighestcorrelation(r =0.759;P<0.0001),followedbythetotaldietaryconcentrationofC18:2andC18:3(r =0.754;P <0.0001),dietIVP(r =0.671;P <0.0001),totaldietaryconcentrationoftheunsaturatedfattyacidsC16:1,C18:1,C18:2,andC18:3(r=0.536;P <0.0001),percentageofthedietMEfromfat(r =0.346;P <0.01),dietaryconcentrationofC18:3(r =0.298;P <0.03),andtotaldietaryconcentrationofC16:1andC18:1(r =0.256;P =0.05).

123

Finishing Pig Nutrition

Asexpected,growthand/orcarcassvariableswerealsofoundtobesignificantlycorre-latedwithbackfat,bellyfat,andjowlfatIV.ForbackfatIV,theendingBWhadthehighestnegativecorrelation(r =-0.318;P <0.01),followedbytheweightrangefed(r =-0.257;P <0.02),backfatdepth(r =-0.245;P <0.02),andADG(r =-0.242;P <0.02).ForbellyfatIV,theendingBWandbackfatdepthhadthehighestnegativecorrelation(r =-0.395;P <0.01),followedbytheweightrangefed(r =-0.317;P <0.03),withtrends(P ≤0.06)foranegativecorrelationfordaysfed(r =-0.271)andapositivecorrelationforFFLI(r =0.272).JowlIVwasnegativelycorrelatedwithbackfatdepth(r =-0.365;P <0.01)andpositivelycorrelatedwithFFLI(r =0.315;P <0.02).

PredictionequationsTheregressionanalysesofdietaryandgrowthcharacteristicsresultedinequationstopredictbackfat,bellyfat,andjowlfatIV(Table3).EquationsusingasinglepredictordemonstratedtheprimaryinfluenceofdietaryunsaturatedfattyacidsontheIVofporkfat.However,improvedequationswereobtainedbyincludingmultiplevariablestodescribethediet,animals,andgrowth.

ThepredictionequationforbackfatIVwasimprovedconsiderablybyincludingmulti-plevariablestocharacterizethediet,aswellastodescribethegrowthandrateatwhichitoccurred.UsingthedietaryconcentrationofC18:2+C18:3(Adjusted R2=0.61)and/orbackfatdepth(Adjusted R2=0.64)resultedinimprovementsoverusingthedietIVPalone(Adjusted R2=0.58).FurtherimprovementswereobtainedbyaddingthedietaryC18:2withorwithoutC18:2+C18:3concentrationstoanequationwiththedietIVP,andreplacingbackfatdepthwithADGandinitialBW(Adjusted R2=0.79).TheequationthatincludedthedietIVP,percentagedietaryC18:2,percentagetotaldietaryC18:2+C18:3,initialBW,andADGresultedinthegreatestR2(Adjusted R2=0.80).Figure1showstheprecisionwithwhichthisequationwasabletopredicttheIVwhencomparedtoactualdata.

ThepredictionequationforbellyfatIVwasimprovedbyincludingmultiplevariablestocharacterizedietandgrowth.AddingthedietarypercentageofMEfromfatasanadjustmenttothedietaryIVP(Adjusted R2=0.80)and/orvariablestodescribetheweightduringwhichthedietwasfedandtheendingbackfatdepthresultedingreaterprecision.TheequationthatincludedthedietIVP,percentageofMEfromfat,BWrange,endingBW,andbackfatdepthresultedinthegreatestR2(Adjusted R2=0.89,Figure2).

ThepredictionequationforjowlfatIVwasimprovedbyincludingmorethanonedietaryvariableandanestimateofcarcasslean.BeginningwiththesimpleequationusingdietaryIVP(Adjusted R2=0.44),replacingitwiththedietaryconcentrationofC18:2oraddingtheestimatedFFLI(Adjusted R2=0.57)resultedinincreasedpreci-sion.FurtherprecisionwasobtainedbyaddingbackthedietIVPandthepercentageofMEfromfat,andusingeitherthebackfatdepth(Adjusted R2=0.71)orestimatedFFLI.TheequationthatincludedthedietIVP,percentageofC18:2,percentageofMEfromfat,andestimatedFFLIresultedinthegreatestR2(Adjusted R2=0.73,Figure3).

124

Finishing Pig Nutrition

Meta-analyses of experiments evaluating dietary IVP-reduction strategies

CorrelationsBackfat,bellyfat,andjowlfatIVwereallhighlycorrelated(r ≥0.880;P <0.001)toeachother(Table4).Asinthepreviousmeta-analysis,dietarycharacteristicshadthehighestcorrelationswiththecarcassbackfat,bellyfat,andjowlfatIV.VariousmeasuresofthefattyacidsintheinitialdietarytreatmenthadthehighestcorrelationswiththebackfatIV,primarilythepercentageofC18:2(r =0.819;P <0.0001),C18:3(r =0.764;P <0.0001),totalC18:2+C18:3(r =0.826;P <0.0001),totalunsaturatedfattyacids(r =0.755;P <0.0001),andthedietIVP(r =0.815;P <0.0001).ThesamedietarycharacteristicsoftheIVPreductiontreatmentwerealsocorrelated(r ≥0.564;P <0.0001)withthebackfatIV,aswellastheMEdensity(r ≥0.605;P <0.001)andpercentageofMEfromfat(r ≥0.402;P <0.03)forboththeinitialandreduction-perioddiets.ForbellyfatIV,theinitialdietarypercentageoftotalC16:1+C18:1(r =0.655;P <0.01),C18:2(r =0.817;P <0.0001),totalC18:2+C18:3(r =0.836;P <0.0001),totalunsaturatedfattyacids(r =0.907;P <0.0001),andthedietIVP(r =0.915;P <0.0001)wereallhighlycorrelated.ThesamedietarycharacteristicsoftheIVP-reductiontreatmentwerealsocorrelated(r ≥0.635;P <0.01)withthebellyfatIV,aswellastheMEdensity(r ≥0.586;P <0.01)andpercentageofMEfromfat(r ≥0.523;P <0.02)forboththeinitialandreduction-perioddiets.ForjowlfatIV,thepercentageofC18:2(r =0.901;P <0.0001),totalC18:2+C18:3(r =0.878;P <0.0001),totalunsaturatedfattyacids(r =0.675;P <0.01),andtheIVP(r =0.785;P <0.0001)oftheinitialdiethadthehighestcorrelations.ThedietarypercentageofC18:2andtotalC18:2+C18:3oftheIVP-reductiontreatmentwerealsocorrelated(r ≥0.464;P <0.03)withthejowlfatIV,aswellasthepercentageofMEfromfat(r =0.511;P <0.02)intheinitialdiet.

OthervariableswerefoundtobecorrelatedwiththebackfatandbellyfatIV.ThetotallengthofthefeedingperiodwasnegativelycorrelatedwiththebackfatIV(r =-0.581;P <0.001)andbellyfatIV(r =-0.518;P <0.02),andthenumberofdaystheinitialdietwasfedwasnegativelycorrelatedwiththebackfatIV(r =-0.494;P <0.01).Addi-tionally,theinitialBW(r =0.627;P <0.0001),overallBWrange(r =-0.594;P <0.001),reduction-perioddietIVP×actualreduction-perioddays(r =0.522;P <0.01),BWattheinitiationofthereductionperiod(r =-0.353;P <0.05),andfinalBW(r =-0.340;P =0.05)werecorrelatedwiththebackfatIV.Asinthepreviousmeta-analysis,backfatdepthwasnegativelycorrelated(r =-0.629;P <0.01)withthebellyfatIV.JowlIVwasnotcorrelatedwithgrowthandcarcassvariables.

PredictionequationsRegressionanalysesofthedietarycharacteristics;growth,carcass,andBWdata;alongwithfeedingdurationsresultedinequationstopredictbackfat,bellyfat,andjowlfatIV(Table5.).Althoughthemeta-analysisofdietIVP-reductiontreatmentswasperformedprimarilywithdatanotincludedinthepreviousmeta-analysis,thepredictionequationsresultinginthegreatestprecisionfordeterminingthebackfat,bellyfat,andjowlfatIVusedthesamedietaryvariables.Similartothepreviousmeta-analysis,theequationswithasinglepredictordemonstratedtheprimaryinfluenceofdietaryunsaturatedfattyacidsontheIVofporkfat.However,thebestsinglepredictorswerederivedfromtheunsaturatedfattyacidcharacteristicsoftheinitialdietratherthanthefinaldiet.

125

Finishing Pig Nutrition

ImprovedequationsforbackfatIVwereobtainedbyusingeithertheIVP,concentra-tionofC18:2,orconcentrationofC18:2+C18:3oftheinitialdietandtheBWattheinitiationofIVPreduction,reduction-perioddietIVP×actualreduction-perioddays,and/orthefinalBWratherthantheIVPoftheinitialdietalone.TheequationthatincludedtheIVPoftheinitialdiet,theBWattheinitiationofIVPreduction,thereduction-perioddietIVP×actualreduction-perioddays,andthefinalBWresultedinthegreatestR2(Adjusted R2=0.90).TheprecisionwithwhichthisequationwasabletopredicttheIVwhencomparedtotheactualdataisshowninFigure4.

Similartothepreviousmeta-analysis,thepredictionequationforbellyfatIVincludedtheIVPoftheinitialdiet.Theprecisionoftheequationwasimprovedbyincludingthereduction-perioddietIVP×actualreduction-perioddays(Adjusted R2=0.90,Figure5).

TheconcentrationofC18:2intheinitialdietwasanimportantdietaryvariableforpredictingjowlfatIV.Thepredictionequationwasimprovedbyincludingthenumberofdaysthattheinitialdietwasfed(Adjusted R2=0.87,Figure6).

DiscussionItiswellestablishedthatthefattyacidcompositionofpigadiposetissuecanbemanip-ulatedbychangingtheamountsandproportionsoffattyacidsinthediet(Woodetal.,20037).Thisisalsoevidentinthemeta-analyses.Theequationswithasinglepredic-tor,similartotheequationdevelopedbyBoydetal.(1997),demonstratetheprimaryinfluenceofthedietaryunsaturatedfattyacidconcentrationontheIVofporkfat.Madsenetal.(19928)reportedthepositivelinearrelationshipbetweenthedietaryandadiposetissuecontentsofpolyunsaturatedfattyacids.ThedietIVPandfatIVdescribethecombinedcharacteristicsofthemono-andpolyunsaturatedfattyacidcontentofaparticularfat.Therefore,itisnotsurprisingthatthedietIVPisacommonpredictorofIVacrossmanyofthepredictionequationsintheanalyses.

AlthoughthedatafromBoydetal.(1997)wereincludedinthemeta-analysesforback-fatandbellyfatIV,theR2oftheequationsusingasinglemeasureofthedietaryunsatu-ratedfattyacidconcentrationasapredictorwasconsiderablylessthanthatreportedbyMadsenetal.(1992)andBoydetal.(1997).TheequationofMadsenetal.(1992)(IV=47.1+0.14×IVP/day, R2=0.86)wasderivedfromDanishexperimentsusingindi-viduallyhousedpigslimit-fedadietaryIVPwithintherangeof37to88(IVP/dayof42to190)from20kgBWuntilharvestat90kgBW.TheequationofBoydetal.(IV=52.4+0.32×IVP,R2=0.99)wasderivedfromasinglecontrolledexperiment,withanIVPintherangeof44to90forpigsfedad libitum from43kgBWuntilharvestat118kgBW.Inthecurrentmeta-analyses,thesimpleequationsforpredictingbackfatIVusingthedietIVPwerederivedfrommultiplestudies.Theequation(backfatIV=57.89+0.18×IVP,R2=0.58)fromthemeta-analysisoffeedingacontinuousIVPincludeddatawithaninitialBWrangeof50to200lb,afinalBWrangeof97to300lb,andadietIVPrangeof5to187.Theequation(backfatIV=54.20+0.23×IVPoftheinitialdiet,R2=0.66)fromthemeta-analysisofIVP-reductionstrate-giesincludeddatawithaninitialBWrangeof85to140lb,afinalBWrangeof227

7Wood,J.D.,R.I.Richardson,G.R.Nute,A.V.Fisher,M.M.Campo,E.Kasapidou,P.R.Sheard,andM.Enser.2003.Effectsoffattyacidsonmeatquality:areview.MeatSci.66:21-32.8Madsen,A.,K.Jakobsen,andH.P.Mortensen.1992.Influenceofdietaryfatoncarcassfatqualityinpigs.Areview.Acta.Agric.Scand.42:220-225.

126

Finishing Pig Nutrition

to290lb,andadietIVPrangeof43to111.Nguyenetal.(20039)demonstratedthatthevariationinthefattyacidcompositionofporkadiposetissueisincreasedwhendatafromvariousexperimentsarepooled,resultinginweakercorrelationsthanthoseobtainedinanindividualexperiment.Theincreasedvariationresultsfromdifferencesintheconditionsacrosstheexperiments.Inthepresentanalyses,accountingforsomeofthesedifferencesresultedinimprovedequationsforpredictingbackfat,bellyfat,andjowlfatIV.

Othervariablesareknowntoinfluencetheamount,composition,andqualityofporkfat.Severalreviewshavebeenpublishedthatdescribesomeofthesevariables.Woodetal.(200810)describedtherelationshipsofbackfatthickness,gender,andtheage,BW,ormaturityofgrowingpigswithfatcomposition.Younger,lighter,andleanerpigswerefoundtohavelowerconcentrationsofC18:0andC18:1andgreaterconcentra-tionsofC18:2intheirsubcutaneousadiposetissue;andthisisalsothecasewhenintactmalesandgiltsarecomparedtocastrates.Fatqualitydefectsaremorecommoninpigsfromveryleanstrainsthatareslaughteredatlowerweightsandwiththinnerbackfat.Thegeneticinfluenceonthefattyacidcompositionofadiposetissueinswinehasbeenpreviouslydescribed(Woodetal.,2003),butthedifferencesobservedbetweengeno-typesarelikelyattributabletotheirdifferencesinleannessandsubcutaneousfatdepth.Genderdifferencesinfatcompositionarealsoafunctionofthedifferencesinsubcuta-neousfatdepthandleanness,anddifferencesfoundbetweenintactmalesandfemaleswiththesamebackfatthicknessindicatethattheadiposetissueofintactmalesmaybelessmaturethanthatofcastratesandfemales.Thecurrentanalysessupporttheconclu-sionthatthebackfatdepthorleancharacteristicsaccountformanyofthedifferencesobservedbetweengenotypesandgenders,andthatbackfatdepthisnegativelycorre-latedwiththeIVofcarcassfat.

Relativelyfewexperimentshaveevaluatedtheeffectsoncarcassfattyacidsofreducingthemajordietarysourcesofunsaturatedfattyacidsforaperiodbeforeslaughter.Sixexperimentswereusedinourmeta-analysesofIVP-reductiontreatments.Thirtyofthe50observationsrepresentedIVP-reductiontreatments,ordietarystrategiestoreducetheeffectsonfatIVoftheinitialdietfed.Theother20observationswerethecontroltreatmentsandwerealsousedinthefirstmeta-analysesofvariouslevelsofdietIVPfedthroughoutthefeedingperiod.Nevertheless,thesamecharacteristicsoftheinitialdietwereimportantformodelingthebackfatIV,bellyfatIV,andjowlfatIVinbothsetsofdata.

Animportantfindingwasthatthecharacteristicsoftheinitialdietweremostimpor-tantforpredictingthefatIVofpigsfedIVP-reductiontreatments.Theactivityoflipogenicenzymesinvolvedinthede novo synthesisofadiposetissueisreducedwithincreasinglevelsofdietaryfattyacids(Alleeetal.,197111).However,datacouldnotbe

9Nguyen,L.Q.,M.C.G.A.Nuijens,H.Everts,N.Salden,andA.C.Beynen.2003.Mathematicalrelationshipsbetweentheintakeofn-6andn-3polyunsaturatedfattyacidsandtheircontentsinadiposetissueofgrowingpigs.MeatSci.65:1399-1406.10Wood,J.D.,M.Enser,A.V.Fisher,G.R.Nute,P.R.Sheard,R.I.Richardson,S.I.Hughes,andF.M.Whittington.2008.Fatdeposition,fattyacidcompositionandmeatquality:Areview.MeatSci.78:343-358.11Allee,G.L.,D.H.Baker,andG.A.Leveille.1971.Influenceoflevelofdietaryfatonadiposetissuelipogenesisandenzymaticactivityinthepig.J.Anim.Sci.33:1248-1254.

127

Finishing Pig Nutrition

foundtodescribethechangesinactivityoftheseenzymesafterareductionofdietaryfattyacidsforgrowing-finishingpigs.Intheexistingdata,althoughnotmeasureddirectly,itwouldappearthatthechangesinlipogenicenzymeactivityarenoteasilyreversedingrowing-finishingpigs.

BackfatIVmaybethemostamenabletochangeusinganIVP-reductionstrategy;andthismaybeaccomplishedbyinitiatingthestrategyatalighterBWandfeedingtoaheavierfinalBW.JowlfatIVappearstobethemostdifficulttomodifyusinganIVP-reductionstrategy,andnutritionistsandproducersmaybelimitedintheirselectionofingredientswhenIVtestingstandardsarebasedonameasurementofjowlfat.

Thedemandforleanpork,coupledwiththeincreasedutilizationofDDGSasaswinefeedingredient,havestimulatedgreaterinterestinunderstandingthefactorsthatinflu-enceporkfatquality.Themeta-analysesdescribedhereprovideforagreaterunder-standingofthefactorsthatareknowntoinfluenceporkfatquality.Furthermore,therelationshipsdescribedinthepredictionequationsobtainedshouldprovetobeusefulforproducingporkwithacceptablefatquality.

128

Fin

ish

ing

Pig

Nu

tr

itio

n

Table1.Crudefat,fattyacid,IV,andIVPvaluesusedforsomeoftheingredientswhenanalyzedvalueswerenotprovided1

Individualfattyacidsofinterest,%offatCrudeFat,% C16:0 C18:0 C16:1 C18:1 C18:2 C18:3 C20:1 C22:1 IVoffat IVP

Barley 1.9 21.8 0.9 0.3 12.8 53.0 5.8 0.0 0.0 118.4 22.5Corn 3.9 10.9 1.8 0.0 24.2 59.0 0.7 0.0 0.0 124.8 48.7CornDDGS2 10.7 10.9 1.8 0.0 24.2 59.0 0.7 0.0 0.0 124.8 133.6Sorghum 2.9 14.4 1.2 1.0 34.2 46.3 2.3 0.0 0.0 116.6 33.8SorghumDDGS 7.3 14.4 1.2 1.0 34.2 46.3 2.3 0.0 0.0 116.6 85.1Soybeanmeal,47.5%CP 3.0 10.3 3.8 0.2 22.8 51.0 6.8 0.0 0.0 125.9 37.8Wheat,hardredwinter 2.0 15.2 0.8 0.5 12.5 39.0 1.8 0.0 0.0 83.3 16.71IV=iodinevalue(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723;AOCS,1998);andIVP=iodinevalueproduct(IVP=[iodinevalueofthedietarylipids]×[percentagedietarylipid]×0.10).2DDGS=drieddistillersgrainswithsolubles.

129

Finishing Pig Nutrition

Table2.Correlationcoefficientsofvariableswithbackfat,bellyfat,orjowlfatIVinthemeta-analysisoftreatmentsformulatedtoasimilardietaryIVPthroughoutthefeedingperiod1

IndependentVariable BackfatIV,n=95 BellyfatIV,n=49 JowlfatIV,n=58DietIVP 0.765(P<0.0001) 0.882(P<0.0001) 0.671(P<0.0001)DietC16:0,% 0.048(P=0.65) 0.182(P=0.21) 0.135(P=0.31)DietC18:0,% -0.097(P=0.35) 0.005(P=0.98) -0.003(P=0.98)TotaldietC16:1+C18:1,% 0.168(P=0.10) 0.335(P<0.02) 0.256(P=0.05)DietC18:2,% 0.689(P<0.0001) 0.608(P<0.0001) 0.759(P<0.0001)DietC18:3,% 0.418(P<0.0001) 0.635(P<0.0001) 0.298(P<0.03)TotalofC18:2+C18:3,% 0.782(P<0.0001) 0.881(P<0.0001) 0.754(P<0.0001)TotalUFA2,% 0.618(P<0.0001) 0.776(P<0.0001) 0.536(P<0.0001)ADG,kg -0.242(P<0.02) 0.171(P=0.24) -0.061(P=0.65)Daysfed -0.082(P=0.43) -0.271(P=0.06) -0.033(P=0.81)MEdensityofdiet,kcal/kg 0.016(P=0.88) 0.324(P<0.03) 0.144(P=0.28)DietMEfromfat,% 0.506(P<0.0001) 0.629(P<0.0001) 0.346(P<0.01)InitialBW,kg -0.027(P=0.79) 0.180(P=0.22) -0.054(P=0.68)FinalBW,kg -0.318(P<0.01) -0.395(P<0.01) -0.148(P=0.27)Weightrangefed,kg -0.257(P<0.02) -0.317(P<0.03) <-0.001(P=1.00)Backfatdepth,mm -0.245(P<0.02) -0.395(P<0.01) -0.365(P<0.01)FFLI3 0.005(P<0.96) 0.272(P<0.06) 0.315(P<0.02)BackfatIV --- 0.907(n=46,P<0.0001) 0.922(n=37,P<0.0001)BellyfatIV 0.907(n=46,P<0.0001) --- 0.887(n=22,P<0.0001)JowlIV 0.922(n=37,P<0.0001) 0.887(n=22,P<0.0001) ---1IVP=iodinevalueproduct(IVP=[iodinevalueofthedietarylipids]×[percentagedietarylipid]×0.10;Christensen,1962);andIV=iodinevalue(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723;AOCS,1998).2UFA=unsaturatedfattyacids(C16:1+C18:1+C18:2+C18:3).3FFLI=fat-freeleanindex.

130

Fin

ish

ing

Pig

Nu

tr

itio

n

Table3.Regressionmodelstodescribetherelationshipofgrowthanddietvariables(fromtreatmentsformulatedtoasimilardietaryIVPthroughoutthefeedingperiod)withbackfat,bellyfat,andjowlfatIV1

Dependentvariable Models C.V. R2

AdjustedR2

BackfatIV =76.58+0.08*dietIVP+1.82*dietC18:2(%)+2.00*[dietC18:2(%)+dietC18:3(%)]+0.10*initialBW(kg)–29.30*ADG(kg) 4.20 0.81 0.80=75.28+0.13*dietIVP+3.04*dietC18:2(%)+0.10*initialBW(kg)–28.54*ADG(kg) 4.31 0.80 0.79=77.76+0.06*dietIVP+3.64*[dietC18:2(%)+dietC18:3(%)]+0.09*initialBW(kg)–28.86*ADG(kg) 4.34 0.80 0.79=75.63+0.12*dietIVP+2.85*dietC18:2(%)–0.07*BWrange(kg)–18.06*ADG(kg) 4.44 0.79 0.78=79.44+5.00*[dietC18:2(%)+dietC18:3(%)]+0.09*initialBW(kg)–30.05*ADG(kg) 4.51 0.78 0.77=75.38+4.80*[dietC18:2(%)+dietC18:3(%)]–19.78*ADG(kg) 5.05 0.72 0.71=75.71+0.19*dietIVP+0.08*initialBW(kg)–24.58*ADG(kg) 5.25 0.70 0.69=72.18+0.18*dietIVP–15.71*ADG(kg) 5.61 0.65 0.65=63.53+4.51*[dietC18:2(%)+dietC18:3(%)]–0.28*BFdepth(mm) 5.65 0.65 0.64=63.09+0.18*dietIVP–0.25*BFdepth(mm) 5.91 0.61 0.61=57.82+4.59*[dietC18:2(%)+dietC18:3(%)] 5.91 0.61 0.61=57.89+0.18*dietIVP 6.11 0.58 0.58

BellyfatIV =50.36+0.23*dietIVP–0.33*dietMEfromfat(%)–0.05*BWrange(kg)+0.18*finalBW(kg)–0.45*BFdepth(mm) 2.78 0.90 0.89=63.06+0.22*dietIVP–0.33*dietMEfromfat(%)+0.05*initialBW(kg)–0.22*BFdepth(mm) 3.08 0.87 0.86=57.10+0.22*dietIVP–0.29*dietMEfromfat(%)+0.06*initialBW(kg) 3.27 0.85 0.84=56.06+0.16*dietIVP+0.05*initialBW(kg) 3.67 0.81 0.80=60.11+0.21*dietIVP–0.25*dietMEfromfat(%) 3.70 0.81 0.80=63.93+0.15*dietIVP–0.22*BFdepth(mm) 3.80 0.80 0.79=58.85+0.16*dietIVP 3.96 0.78 0.77

JowlfatIV =2.70+0.18*dietIVP+2.15*dietC18:2(%)–0.33*dietMEfromfat(%)+1.10*estimatedFFLI 2.71 0.75 0.73=72.57+0.17*dietIVP+2.01*dietC18:2(%)–0.32*dietMEfromfat(%)–0.69*BFdepth(mm) 2.78 0.73 0.71=-9.82+0.26*dietIVP–0.37*dietMEfromfat(%)+1.36*estimatedFFLI 2.90 0.70 0.69=20.65+4.12*dietC18:2(%)+0.76*estimatedFFLI 3.23 0.62 0.61=59.93+4.89*dietC18:2(%)–0.12*dietMEfromfat(%) 3.35 0.60 0.58=-5.32+0.16*dietIVP+1.28*estimatedFFLI 3.38 0.59 0.57=59.74+4.28*dietC18:2(%) 3.40 0.58 0.57=61.95+0.15*dietIVP 3.88 0.45 0.44

1IVP=iodinevalueproduct(IVP=[iodinevalueofthedietarylipids]×[percentagedietarylipid]×0.10;Christensen,1962);andIV=iodinevalue(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723;AOCS,1998).

131

Finishing Pig Nutrition

Table4.Correlationcoefficientsofvariableswithbackfat,bellyfat,orjowlfatIVinthemeta-analysisofIVPreductionstrategies1

IndependentVariable BackfatIV,n=33 BellyfatIV,n=21 JowlfatIV,n=23InitialdietIVP 0.815(P<0.0001) 0.915(P<0.0001) 0.785(P<0.0001)Reduction-perioddietIVP 0.661(P<0.0001) 0.818(P<0.0001) 0.300(P=0.17)InitialdietC16:0,% -0.416(P<0.02) 0.468(P<0.04) -0.305(P=0.16)Reduction-perioddietC16:0,% 0.304(P=0.09) 0.414(P=0.06) -0.130(P=0.55)InitialdietC18:0,% -0.642(P<0.0001) 0.253(P=0.27) -0.459(P<0.03)Reduction-perioddietC18:0,% 0.252(P=0.16) 0.300(P=0.19) -0.198(P=0.37)InitialdietC16:1+C18:1,% -0.231(P=0.20) 0.655(P<0.01) -0.126(P=0.57)Reduction-perioddietC16:1+C18:1,% 0.035(P=0.85) 0.635(P<0.01) -0.088(P=0.69)InitialdietC18:2,% 0.819(P<0.0001) 0.817(P<0.0001) 0.901(P<0.0001)Reduction-perioddietC18:2,% 0.711(P<0.0001) 0.755(P<0.0001) 0.468(P<0.03)InitialdietC18:3,% 0.764(P<0.0001) 0.338(P=0.13) 0.367(P=0.09)Reduction-perioddietC18:3,% 0.680(P<0.0001) 0.328(P=0.15) 0.332(P=0.12)InitialdietC18:2+C18:3,% 0.826(P<0.0001) 0.836(P<0.0001) 0.878(P<0.0001)Reduction-perioddietC18:2+C18:3,% 0.716(P<0.0001) 0.763(P<0.0001) 0.464(P<0.03)InitialdietUFA2,% 0.755(P<0.0001) 0.907(P<0.0001) 0.675(P<0.01)Reduction-perioddietUFA,% 0.564(P<0.001) 0.862(P<0.0001) 0.204(P=0.35)OverallADG,kg -0.217(P=0.23) -0.018(P=0.94) -0.143(P=0.52)MEdensityofinitialdiet,kcal/kg 0.605(P<0.001) 0.626(P<0.01) -0.048(P=0.83)MEdensityofreducedIVPdiet,kcal/kg 0.647(P<0.0001) 0.586(P<0.01) 0.070(P=0.75)InitialdietMEfromfat,% 0.402(P<0.03) 0.523(P<0.02) 0.511(P<0.02)Reduction-perioddietMEfromfat,% 0.633(P<0.0001) 0.729(P<0.01) 0.111(P=0.61)Totaldays -0.581(P<0.001) -0.518(P<0.02) 0.313(P=0.15)Daysinitialdietfed -0.494(P<0.01) -0.119(P=0.61) 0.091(P=0.68)Daysreduction-perioddietfed 0.300(P=0.09) -0.072(P=0.76) 0.022(P=0.92)InitialBW,kg 0.627(P<0.0001) 0.373(P=0.10) -0.282(P=0.19)BWatinitiationofIVPreduction,kg -0.353(P<0.05) 0.052(P=0.82) -0.037(P=0.87)FinalBW,kg -0.340(P=0.05) -0.388(P=0.08) 0.043(P=0.85)Backfatdepth,mm 0.067(P=0.71) -0.629(P<0.01) -0.202(P=0.35)FFLI3 -0.075(P=0.68) 0.410(P=0.06) 0.200(P=0.36)Overallweightrange,kg -0.594(P<0.001) -0.388(P=0.08) 0.290(P=0.18)Weightrangeforreductionperiod,kg 0.228(P=0.20) -0.098(P=0.67) 0.049(P=0.82)Reduction-periodIVP*reductiondays 0.522(P<0.01) 0.075(P=0.75) 0.071(P=0.75)BackfatIV --- 0.880(n=12,P<0.001) 0.963(n=15,P<0.0001)BellyfatIV 0.880(n=12,P<0.001) --- 0.987(n=6,P<0.001)JowlIV 0.963(n=15,P<0.0001) 0.987(n=6,P<0.001) ---1IVP=iodinevalueproduct(IVP=[iodinevalueofthedietarylipids]×[percentagedietarylipid]×0.10;Christensen,1962);andIV=iodinevalue(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723;AOCS,1998).2UFA=unsaturatedfattyacids(C16:1+C18:1+C18:2+C18:3).3FFLI=fat-freeleanindex.

132

Fin

ish

ing

Pig

Nu

tr

itio

n

Table5.RegressionmodelstodescribetherelationshipofvariablesinvolvedinIVP-reductionstrategieswithbackfat,bellyfat,andjowlfatIV1

Dependentvariable Model C.V. R2 AdjustedR2

BackfatIV =63.57+0.25*initialdietIVP+0.28*BWatinitiationofIVPreduction(kg)+0.003*(reduction-perioddietIVP*reductiondays)–0.36*finalBW(kg)

2.75 0.91 0.90

=67.66+0.28*initialdietIVP+0.12*BWatinitiationofIVPreduction(kg)–0.25*finalBW(kg) 4.04 0.80 0.77=71.49+4.94*[initialdietC18:2(%)+initialdietC18:3(%)]+0.11*BWatinitiationofIVPreduction(kg)–0.22*finalBW(kg)

4.10 0.79 0.77

=38.74+4.51*[initialdietC18:2(%)+initialdietC18:3(%)]+0.16*BWatinitiationofIVPreduction(kg)+0.001*(reduction-perioddietIVP*reductiondays)

4.38 0.76 0.74

=33.14+0.25*initialdietIVP+0.17*BWatinitiationofIVPreduction(kg)+0.001*(reduction-perioddietIVP*reductiondays)

4.48 0.75 0.72

=78.53+3.97*[initialdietC18:2(%)+initialdietC18:3(%)]–0.16*finalBW(kg) 4.62 0.72 0.71=47.86+4.88*[initialdietC18:2(%)+initialdietC18:3(%)]+0.08*BWatinitiationofIVPreduction(kg) 4.66 0.71 0.70=76.67+0.22*initialdietIVP–0.18*finalBW(kg) 4.70 0.71 0.70=41.85+0.28*initialdietIVP+0.08*BWatinitiationofIVPreduction(kg) 4.76 0.71 0.69=47.05+5.51*initialdietC18:2(%)+0.07*BWatinitiationofIVPreduction(kg) 4.77 0.71 0.69=58.19+4.15*[initialdietC18:2(%)+initialdietC18:3(%)] 4.87 0.68 0.67=57.38+4.69*initialdietC18:2(%) 4.96 0.67 0.66=54.20+0.23*initialdietIVP 5.01 0.66 0.65

BellyfatIV =43.31+0.39*initialdietIVP–0.001*(reduction-perioddietIVP*reductiondays) 2.65 0.91 0.90=44.49+0.35*initialdietIVP 3.47 0.84 0.83

JowlfatIV =52.43+4.99*initialdietC18:2(%)+0.06*daysfedtheinitialdiet 2.26 0.89 0.87=57.89+4.71*initialdietC18:2(%) 2.83 0.81 0.80=58.69+0.19*initialdietIVP 4.04 0.62 0.60

1IVP=iodinevalueproduct(IVP=[iodinevalueofthedietarylipids]×[percentagedietarylipid]×0.10;Christensen,1962);andIV=iodinevalue(IV=[C16:1]×0.95+[C18:1]×0.86+[C18:2]×1.732+[C18:3]×2.616+[C20:1]×0.785+[C22:1]×0.723;AOCS,1998).

133

Finishing Pig Nutrition

Pre

dic

ted

bac

kfat

IV

100.0

95.0

90.0

85.0

80.0

75.0

70.0

65.0

60.0

55.0

50.0

77 100.0187175163151139126114102 90

Actual backfat IV

Figure1.Predictedvs.actualbackfatIVusingthemodel[Y=76.58+0.08*dietIVP+1.82*dietC18:2(%)+2.00*[dietC18:2(%)+dietC18:3(%)]+0.10*initialBW(kg)–29.30*ADG(kg)]anddatafromthemeta-analysisoftreatmentsformulatedtosimilardietaryIVPthroughoutthefeedingperiod.

Pre

dic

ted

bel

ly fa

t IV

92.5

87.5

82.5

77.5

72.5

67.5

62.5

57.5

57.5 92.587.582.577.572.567.562.5

Actual belly fat IV

Figure2.Predictedvs.actualbellyfatIVusingthemodel[Y=50.36+0.23*dietIVP–0.33*dietMEfromfat(%)–0.05*BWrange(kg)+0.18*finalBW(kg)–0.45*BFdepth(mm)]anddatafromthemeta-analysisoftreatmentsformulatedtosimilardietaryIVPthroughoutthefeedingperiod.

134

Finishing Pig Nutrition

Pre

dic

ted

jow

l fat

IV

82.5

77.5

72.5

67.5

62.5

82.577.572.567.562.5

Actual jowl fat IV

Figure3.Predictedvs.actualjowlfatIVusingthemodel[Y=2.70+0.18*dietIVP+2.15*dietC18:2(%)–0.33*dietMEfromfat(%)+1.10*estimatedFFLI]anddatafromthemeta-analysisoftreatmentsformulatedtosimilardietaryIVPthroughoutthefeedingperiod.

Pre

dic

ted

bac

kfat

IV

90.0

85.0

80.0

75.0

70.0

65.0

60.0

60.0 90.085.080.075.070.065.0

Actual backfat IV

Figure4.Predictedvs.actualbackfatIVusingthemodel[Y=63.57+0.25*initialdietIVP+0.28*BWatinitiationofIVPreduction(kg)+0.003*(reduction-perioddietIVP*reductiondays)–0.36*finalBW]anddatafromthemeta-analysisofIVP-reductionstrategies.

135

Finishing Pig Nutrition

Pre

dic

ted

bel

ly fa

t IV

81.5

76.5

71.5

66.5

61.5

56.5

56.5 81.576.571.566.561.5

Actual belly fat IV

Figure5.Predictedvs.actualbellyfatIVusingthemodel[Y=43.31+0.39*initialdietIVP–0.001*(reduction-perioddietIVP*reductiondays)]anddatafromthemeta-analysisofIVP-reductionstrategies.

Pre

dic

ted

jow

l fat

IV

85.0

80.0

75.0

70.0

65.0

65.0 85.080.075.070.0

Actual jowl fat IV

Figure6.Predictedvs.actualjowlfatIVusingthemodel[Y=52.43+4.99*initialdietC18:2(%)+0.06*daysfedtheinitialdiet]anddatafromthemeta-analysisofIVP-reductionstrategies.