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Macronutrient intake of dogs, self-selecting diets varying in composition offered ad libitum

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Abstract

The diet of the domestic dog has changed significantly from that of its wolf ancestor, with to date only two studies having examined macronutrient self-selection in dogs. Whilst the first focused solely on protein intake, determining an intake of 30% metabolisable energy (ME), the second investigated dietary protein, fat and carbohydrate (PFC), indicating an intake ratio of 30:63:7% by energy. This study's aim was to further elucidate macronutrient intake by providing greater macronutrient range, energy content, and to investigate over a longer duration than previous studies. Fifteen adult dogs were given access to three wet diets providing 500% of daily ME, twice daily over 10 days. The diets were nutritionally complete and formulated using the same four ingredients in different proportions to supply high levels of protein (58% ME), fat (86% ME) or carbohydrate (54% ME). Overall fat and carbohydrate consumption significantly declined from 6,382 to 917 kcals per day (p < 0.001) and 553 to 214 kcals day⁻¹ (p < .01) respectively. Protein intake, however, remained constant over the study and ranged from 4,786 to 4,156 kcals day⁻¹. Such results impacted on percentage total energy intake, with fat decreasing from 68% to 52% (p < .001) and protein increasing from 29% to 44% (p < .01). Our findings suggest that dogs still possess a “feast or famine” mentality, wherein energy dense fat is prioritised over protein initially. With continued feeding over 10 days, a transition to a more balanced energy contribution from both macronutrients is evident. The study also shows that given the option, dogs do not select carbohydrate to be a significant portion of the diet. The health implications of such dietary selection are of interest.
J Anim Physiol Anim Nutr. 2017;1–8. wileyonlinelibrary.com/journal/jpn 
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 1
Received:16October2016 
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  Accepted:11July2017
DOI: 10.1111/jpn.12794
ORIGINAL ARTICLE
Macronutrient intake of dogs, self- selecting diets varying in
composition offered ad libitum
M. T. Roberts1,2 | E. N. Bermingham1| N. J. Cave2| W. Young1| C. M. McKenzie3|
D.G. Thomas2
1Food Nutrition & Health Team, Food &
Bio-basedProducts,AgResearchGrasslands,
Palmerston North, New Zealand
2InstituteofVeterinaryAnimalBiomedical
Sciences, Massey University, Palmerston
North, New Zealand
3Bioinformatics&StatisticsTeam,AgResearch
Grasslands,PalmerstonNorth,NewZealand
Correspondence
DavidThomas,AnimalProductionandHealth,
InstituteofVeterinary,AnimalandBiomedical
Sciences, Massey University, Palmerston
North, New Zealand.
Email:d.g.thomas@massey.ac.nz
Funding information
AgriculturalandMarketingResearch
andDevelopmentTrust,Grant/Award
Number:A15013;K9NaturalFoodLimited;
AgResearchLimited,Grant/AwardNumber:
A21247
Summary
Thedietofthedomesticdoghaschangedsignificantlyfromthatofitswolfancestor,
withto dateonlytwostudies having examinedmacronutrientself-selectionin dogs.
Whilstthefirstfocusedsolelyonprotein intake, determining an intake of 30% me-
tabolisableenergy(ME),thesecondinvestigateddietaryprotein,fatandcarbohydrate
(PFC),indicatinganintakeratioof30:63:7%byenergy.Thisstudy’saimwastofurther
elucidatemacronutrientintakebyprovidinggreatermacronutrientrange,energycon-
tent, and to investigate over a longer duration than previous studies. Fifteen adult
dogswere given access to threewet diets providing 500% ofdaily ME, twice daily
over10days.The diets were nutritionally complete andformulatedusing the same
fouringredientsindifferentproportionstosupplyhighlevelsofprotein(58%ME),fat
(86%ME)orcarbohydrate(54%ME).Overallfatandcarbohydrateconsumptionsig-
nificantly declined from 6,382 to 917kcals per day (p<0.001) and 553 to
214kcalsday−1(p<.01) respectively. Protein intake, however, remained constant
overthestudyandrangedfrom4,786to4,156kcalsday−1. Such results impacted on
percentagetotal energy intake, withfatdecreasingfrom68%to 52% (p<.001) and
proteinincreasingfrom29%to44%(p<.01).Ourfindingssuggestthatdogsstillpos-
sessa“feastorfamine”mentality,whereinenergydensefatisprioritisedoverprotein
initially.Withcontinuedfeedingover10days,atransitiontoamorebalancedenergy
contributionfrombothmacronutrientsisevident.Thestudyalsoshowsthatgiventhe
option,dogs do not select carbohydrateto be a significantportionof the diet. The
health implications of such dietary selection are of interest.
KEYWORDS
dietarycomposition,dog,macronutrient,self-selection
1 | INTRODUCTION
Whilst archaeological records cannot determine whether domestic
dogsoriginated from a single wolfpopulationorarose from multiple
populations at different times (Frantz etal., 2016; Vilà etal., 1997),
dogs are the only largecarnivore to have been domesticated, most
likelyoverawidegeographicarea(vonHoldtetal.,2010).Byinheriting
suchwolfancestry,thedomesticdogisclassifiedasa carnivore,with
teeth adapted for grasping and tearing; however, they also possess
omnivoroustraits(Serpell,1995).The doghasarequirementforboth
proteinandfat(AssociationofAmericanFeedControlOfficials,2016;
NationalResearchCouncil,2006),butnotforcarbohydrate,despitere-
centfindingsthatshowthatdomesticdogsmayhaveevolutionaryad-
aptationsforimprovedcarbohydratedigestion(Axelssonetal.,2013).
ThisisanopenaccessarticleunderthetermsoftheCreativeCommonsAttributionLicense,whichpermitsuse,distributionandreproductioninanymedium,
providedtheoriginalworkisproperlycited.
©2017TheAuthors.Journal of Animal Physiology and Animal NutritionPublishedbyBlackwellVerlagGmbH.
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   ROBERTS ET al.
The macronutrient composition of modern dog foods canvary
significantlydepending onthe format fed.This is largely due to the
manufacturingprocessesrequiredtoproducethefood.Forexample,
kibbled diets typically contain 16%–38% protein, 6%–18% fat and
40%–60% carbohydrate (dry matter basis). However,wet/raw diets
typically containno or low levels (<10%) of carbohydratecombined
with higher levels of protein and fat (45% and 50% respectively).
Fromadietaryperspectivecommercialdrydogfoodisbyfarthemost
popularfeedingoption,beingfedto over88%ofdogs(NewZealand
CompanionAnimalCouncil2016).Indeedwhilstanyimpactonhealth
fromfeedingadifferingdietaryformat(dryorwet)andmacronutrient
composition has yet to be determined, obesity and its many associated
conditions such as diabetes, cardiorespiratory disease and urinary dis-
ordersare an increasing health risk forcompanion animals (German,
2006). Indeed in the past 10years, approximately 30%–40% of pet
dogsareclassifiedasbeing overweight,whilstanadditional5%–20%
termed obese (Witzel etal., 2014).Although the establishment of a
targetedmacronutrientintakewillnotinitselfhighlightanyimpacton
health,itmayserveas astartingpointforfutureresearch,wherebya
specific dietary macronutrient composition could be assessed in refer-
encetotheimpactonmarkersofhealth.
The ability of animals to select a macronutrient ratio that optimises
fitness costs (such as lifespanand rate of reproduction) has to date
beenproveninarangeofspecies(Leeetal.,2008;Simpson,Sibly,Lee,
Behmer,& Raubenheimer,2004).Moreover,establishing the macro-
nutrientprofile“targeted”bydogscouldhighlightthepotentialdiffer-
ence between what they want to consume, and what most commercial
diets are providing. Further questions may also be addressed as to
whetheradogwouldunder-eatsomenutrients,andover-eatothersin
an attempt to reach an intuitive predetermined macronutrient profile
when provided with an inappropriate dietary composition.
Froma nutritional standpoint, whilst feeding biologically appro-
priate diets to pet dogs has not currently been shownto provide
any health benefits, raw meat diets have been demonstrated to be
highlydigestible,resultinginlowfaecalvolumeand desirablefaecal
quality(Beloshapka,Duclos,VesterBoler,&Swanson,2012).Inaddi-
tion,itisclearlyapparentthatdomesticateddogsarecurrentlyeating
diets that differ substantially from what their ancestors consumed.
Highlightingthis,Bosch,Hagen-Plantinga,andHendriks(2015)found
that the dietary composition of wild wolves showed the selected
protein–fat–carbohydrateprofilewas54:45:1byenergy.
To date, only two studies have examined dietary macronutrient
selectioninthedog.Whilstthe firststudy appeared to demonstrate
apreferenceforproteinovercarbohydrates(consuming30% protein
by energy), the impact of fat was not fully determined (Romsos &
Ferguson,1983).Amorerecentstudydid,however,allowforallthree
macronutrientstobeself-selectedbydogsofdifferingbreeds,suggest-
ingan overallprotein/fat/carbohydrateratio(P:F:C) ofapproximately
30:63:7%byenergywhenfedcompleteandbalancedwet-baseddiets
(Hewson-Hughesetal.,2012). However,the restriction of dailytotal
foodintakeincertainexperimentalstages (e.g.,100%ofMERforthe
firstsix3-daycyclesofthelearningphase)mayhavelimitedtheextent
by which the animals could fully select the provided diets. In addition,
the structuring ofdifferent feeding phases and diet composition se-
lectedmaypotentiallyhaveinfluencedthedogsfeedingpatterns.
Existingliteraturesuggeststhatwhendogsareprovidedwiththe
ability to self-select a macronutrient ratio, theywill consume 30%
oftheir maintenance energy requirements from protein.However,a
numberofcommercialwetdiets containin excessofthisvalue,with
reportsfromdogownersthatanincreaseinpalatabilityislinkedwith
this factor. Therefore, the hypothesis of the study was that dogs
wouldselectadietconsistingofmorethan30%oftotalenergyfrom
protein. The aim of this study was, therefore, to establish the self-
selectivemacronutrientintakeofdogsbyprovidingthemwitharange
ofdiets, each specifically higherinenergysourced fromproteinand
fatoveralongerduration.Thisconsequentlywillenabletheintuitive
macronutrient capabilities ofthe domestic dog to be examined in a
deeper manner than has previously been conducted. Subsequently
ourfindingswill eitherreinforceorchallengethoseofthepreviously
conductedstudies,withthe potentialtohighlight thatadogmaystill
possessasimilarmacronutrientintaketothatoftheirwildancestors.
2 | MATERIALS AND METHODS
2.1 | Ethics
EthicalapprovalwasgainedfromtheMasseyUniversityAnimalEthics
Committee (MUAEC 15/75), before commencing the experiment.
The dogs were housed at Massey University Canine Nutrition Unit
(Palmerston North, New Zealand), in accordance with the Animal
Welfare(CompanionDogs)CodeofWelfare(2007).
2.2 | Animals
Fifteen Harrier hound dogs (five male and 10 female) were used
throughout the study, comprising of four neutered and one entire
maleandthreeneuteredandsevenentirefemales.Thedogswereall
deemedhealthy based on a physical examination. The mean ageof
thedogsusedinthestudywas7.68years±0.73SEM.Thedogswere
housedinpairsin10mx10m(100m2)outdoorpensoringroupsof
4in grass paddocksmeasuring700m2 for 8hraday. Overnight the
dogswerehousedindoorsinpairswithwaterandbeddingprovided.
2.3 | Diets
Ahighprotein(HP),highfat(HF)andhighcarbohydrate(HC)diet(Table1)
was formulated to meet AAFCO Dog Food Nutrient Profiles for adult
maintenance(AssociationofAmerican FeedControlOfficials,2015).All
diets consisted of the same four ingredients at different inclusion lev-
els, namely maize, lamb loin fat, green tripe and venison mechanically
debonedmeat(MDM)(TableS1).Thelevelsofprotein,fat,ash,moisture
andNFE(nitrogenfreeextract)wereanalysedforeachdiet(Table1).
A 5-dayperiod was used to adapt the dogs onto the test diets,
consistingofa20%dayondayincreaseofanequalmixtureoftheHF,
HPand HC diets,whilst concurrently decreasingtheirexistingcom-
mercialdrydiet(protein–fat–carbohydrateprofile21:23:56byenergy)
    
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ROBERTS ET al.
by20%. Therefore,by the last day of the adaption period, the dogs
werebeingfedsolelyanequalcombinationoftheexperimentaldiets,
at which point they were deemed to have been fully transitioned.
The10-dayexperimentalphaseofthestudythenstarted,consist-
ingofthe dogsbeingoffered250% oftheir dailyME requirementof
eachdiet,twiceaday(8a.m.and2p.m.;1,500%ME,totalperdayfor
allthreediets).Allthreedietswereofferedsimultaneously.
2.4 | Experimental protocol
Thedogswereweighedatthestart(day1),middle(day 5) and end
(day10)oftheexperimentalperiod(Table2).In orderto assessself-
selected macronutrient consumption, three large plastic bowls each
containing250%ofthe dailyenergyrequirement oftheHF, HCand
HPdietswereprovidedtoeachdog(twicedaily,at8a.m.and2p.m.)
for 10days (Figure1). The position of each bowl was interchanged
at each feeding time to prevent positional bias. A number of feed-
ingdynamicswerealsoobservedbothdirectlybyanobserverduring
eachfeeding period andafterwardsvia the use ofavideo recording
camera(SonyHandycamHDR-SR11E/SR12E)toverifyresults.These
observations involved which diets were approached first, which
diets consisted of any consumption first and which diets were com-
pletelyavoided.Dogswereofferedthedietsuntilsatiatedstatuswas
achieved. This was defined as the point whereby the animal lost inter-
est in any of the diets.
2.5 | Calculations
Protein, fat and carbohydrate energy intakes were determined by
applying modified Atwater factors (protein/carb 3.5Kcalg−1 fat
8.5Kcalg−1) (National Research Council, 2006). As these data were
knownforeachspecificdiet,totalenergyconsumptionwascalculated
bysubtracting thetotalof eachdietprovided toeachdog from that
remaining after each dietary exposure. Additionally macronutrient
ratiowas determined as the overall percentageenergy contribution
thateachmacronutrientmadetoeach diet.Therefore,byaddingthe
differentquantitiesofeachdietconsumedandtherespectiveprotein,
fatandcarbohydrateenergycontribution,thetotalenergyfromeach
macronutrient could be established.
2.6 | Statistical analysis
Separate analyses were conducted for each of the response variables
(i.e.,protein,fat,carbohydrateandprotein:fatratio)againstmeasure-
mentday,usingarandomcoefficientsregressionmodelwhichallowed
forseparate slopes and intercepts to be fitted for each dog.As the
experimentinvolved dogsofboth sexes(5maleand10 female), the
factors“sex”and“reproductive”wereassessedseparately,butnosig-
nificant differences were found, so these factors were not included in
themodel.Modellingwasundertakenusingrsoftware(RCoreTeam,
2016).Alldatawerereportedas interceptand slopewith associated
standarderror(SE).
Fisher’sexacttestwas used to compare the proportionsoffirst
approachedandfirstconsumedforeachofthediets(HP,HFandHC).
Thetestwasperformedwiththestatisticalsoftwarepackageminitab®
16(2010).
Binarylogisticregressionanalysiswasusedtotesttheeffectofdiet
on diet avoidance, with diet avoidance as the binary response variable
(avoidedvs.notavoided)andthediet(HP,HFandHC)aspredictor.
Bodyweight was analysed with a repeated measurements lin-
earmixed model (REML) with the factormeasurementday (levels1,
TABLE1 Macronutrientprofilesofhighprotein(PFC
57.6:41.7:0.7%),highfat(PFC12.8:86.7:0.5%)orhighcarbohydrate
(PFC17.8:27.7:54.5%)dietsofferedat500%maintenanceenergy
requirementstoadultdogs(n=15)for10days
Nutrient DM (g/100 g) HF HC HP
Moisture(asfed) 41.2 26.2 73.0
Protein 23.9 19.3 71.2
Fat(etherextract) 66.4 12.4 21.2
Ash 7.5 4.8 5.5
Carbohydrate 0.9 59.3 0.9
Crudefibre 1.3 4.2 1.2
ME(Kcalkg−1)a6,512 3,805 4,325
DM,DryMatter; HP,HighProtein;HF,High fat;HC,HighCarbohydrate;
ME,Metabolisableenergy.
aCalculated from modified Atwater factors (National Research Council,
2006)
TABLE2 Meanbodyweightofdogs(n=15)offeredhighprotein
(PFC57.6:41.7:0.7%),highfat(PFC12.8:86.7:0.5%)orhigh
carbohydrate(PFC17.8:27.7:54.5%)dietsat500%maintenance
energyrequirementsfor10days
Day 1 Day 5 Day 10 p- value
Mean 25.9c27.0b27.5a<.001
SEM 0.72 0.77 0.77
SEM, Standard error of mean.
Thesuperscriptsaresignificantlydifferentfromoneanother(p<.05).
FIGURE1 Experimentaldesigninvolvingdogsofferedhigh
proteinHP(PFC57:42:1%byenergy),highfatHF(PFC13:86:1%by
energy)orhighcarbohydrateHC(PFC18:28:54%byenergy)dietsfor
10 days
TEST DOG OBSERVOR
RECORDING
CAMERA HC
WATER HF
HP
4 
|
   ROBERTS ET al.
5and 10). Analysiswasconducted using GenStat18thedition(VSN
International,2016). Results are presented as means and associated
standarderrorofthemean(SEM).
3 | RESULTS
3.1 | Bodyweight
Bodyweightincreased significantly (p<.001) over the 10-day study
(Table2).Atthestartofthestudy,themeanbodyweightofthedogs
was 25.9kg±0.72 SEM which increased to 27.5kg±0.77 SEM on
day 10.
3.2 | Energy intake
Over the course of the study, the dogs reduced (p<.001; Table3)
theirpercentageofenergyconsumedfrom363to162percentofen-
ergyintakeaccordingtothequadraticequation:%ME=419.1(±31.8
SEM)–60(±8.78SEM)xDay+3.43(±0.78SEM)xDay2(Figure2).
3.3 | Feeding dynamics
Throughout the duration of the experiment, the percentage of
dogswhich first approached and first consumed a diet wasdeter-
mined(Figure3).ForHP,thepercentageofdogswhichapproached
thediet firstwas47%(±3.7 SEM)andfirstconsuming it64%(±6.0
SEM)(p<.001),forcarbohydrate24%(±3.0 SEM) first approached
thediet, with 4% (±1.9SEM)first consuming it (p<.001). Thehigh
fatdietdisplayednosignificantdifferencesbetweenthose firstap-
proached 29% (± 3.5 SEM) and first consumption 30% (±5.5 SEM)
FIGURE2 Overthe10-dayperiod,thepercentageofenergy
consumedbythedogs(n=15)reduced(p<.001)according
tothequadraticequation:%ME=419.1(±31.8SE)–60(±8.78
SE)xDay+3.43(±0.78SE)whenofferedhighprotein(P:F:C
57:42:1%byenergy),highfat(P:F:C13:86:1%byenergy)orhigh
carbohydrate(P:F:C18:28:54%byenergy)dietsfor10days
0
50
100
150
200
250
300
350
400
450
0246
810
Day
Mean % of energy consumed
FIGURE3 Percentageofhighprotein(P:F:C57:42:1%byenergy),
highfat(P:F:C13:86:1%)orhighcarbohydrate(P:F:C18:28:54%
byenergy)experimentaldietswhichwereapproachedfirstbyadult
dogs(n=15)for10dayswere47±3.7%,29±3.5%and24±3.0%.
Thoseinvolvinganyleveloffirstconsumptionwere64.3±6.0%,
29.7±5.5%and3.7±1.9%.Forboththehighproteinandhigh
carbohydratediets,thereweresignificantdifferencesbetweenthe
percentagefirstapproachedandfirstconsumed(p<.001)
0
10
20
30
40
50
60
70
80
High protein High fatHigh carb
Percentage
Diet
1st diet approached
1st diet consumed
FIGURE4 Percentageofhighprotein(PFC57:42:1%),highfat
(PFC13:86:1%)orhighcarbohydrate(PFC18:28:54%)experimental
dietscompletelyavoidedbydogs(n=15)over10days.The
percentageofhighcarbohydratedietswhichwerecompletely
avoidedwassignificantlydifferenttothepercentageofhighfat
diets,whichinturnwassignificantlydifferenttothehighproteindiet
(p<.001)
0
10
20
30
40
50
60
70
High proteinHigh fa
tH
igh carbohydrate
Percentage
Diet
b
a
FIGURE5 Meanmacronutrientdailyconsumption(kcalsday−1)
foradultdogs(n=15)offeredhighprotein(P:F:C57:42:1%by
energy),highfat(P:F:C13:86:1%byenergy)orhighcarbohydrate
(P:F:C18:28:54%byenergy)dietsfor10days.Theconsumptionof
carbohydrate(kcals=284.09(±64.12SE)–26.04(±8.33SE)xDay),
andfat(kcals=6,989.38(±1,197.65SE)–607.24(±124.10SE)xDay)
declinedoverthestudy(p < .01 and p<.001respectively).
Consumptionofproteinremainedconstant(kcalsday−1=4,856.21
(±921.20SE)–70.00(±96.95SE)xDay)
0
2000
4000
6000
8000
10,000
12,000
14,000
12345678
91
0
Kcals per day
Day
Fat Protein Carbohydrate
    
|
 5
ROBERTS ET al.
(p=.720).Significantdifferences(p<.001)wereobservedbetween
thepercentageofeachdietcompletelyavoided,with58%(±2.9SE)
of the carbohydrate diet being completely avoided, 20% (±2.3 SE)
of the fat diet and 3% (±1.0 SE) of the protein diet (Figure4). No
changesin this behaviour were observedover the duration of the
study(p=.206).
3.4 | Kcals per day of each macronutrient consumed
Over the course of the study, the daily consumption of carbohydrate
reduced(p<.01; Figure5) from 554 on day 1 to214kcalsday−1 on
day10(kcals=284.09(±64.12 SE)–26.04(±8.33SE)xDay (Table3).
Thekcalsper day of fat consumed also reduced (p<.001; Figure5)
from6,382onday1to917kcalsday−1onday10(kcals=6,989.38
(±1,197.65 SE)–607.24 (±124.10 SE)xDay (Table3). Consumption
ofprotein remained constant over the study ranging from 4786on
day1to4,156kcalsday−1onday10(kcalsday−1=4,856.21(±921.20
SEM)–70.00(±96.95SEM)xDay(Table3).
3.5 | Macronutrient consumption and ratio
Protein intake (as a proportion of total ME) increased (p<.01;
Figure6)from29.4%MEonday 1to 44%ME(ME%=27.77(±3.17
SE)+1.60(±0.36SE)xDay; Table3)byday10.Fatintakedecreased
(p<.001;Figure6)from68%MEonday1to52%ME(ME%=69.95
(±3.14SEM)–1.81(±0.37SE)xDay)(Table3)byday10.Nosignificant
difference in carbohydrate intake was observed (Figure6) over the
study(2.5%MEonday1and4.4%MEbyday10:ME%=2.28(±0.62
SE)+0.21(±0.27SE)xDay;Table3).
The P:F ratio reflects these differences, increasing significantly
(p<.001)fromday1 to10ofthestudy(P:F=0.40(±0.07SE)+0.05
(±0.01SE)xDay;Table3).AP:F:Cratioof34:62:4%wasselectedby
thedogsonday1, which gradually changed to 45:51:4% by day10
(see Figure6, raw data solid lines), driven by this increase (p<.01)
in protein intake (ME day−1) and decrease (p<.001) in fat intake
(MEday−1).
Using the fitted regression line of Protein%=27.8+1.6 Day,
Protein%intakeonDay5was calculatedtobe 35.8%,increasingto
43.8%byday10(Table3,Figure6).
4 | DISCUSSION
Our study shows that when dogs are allowed to self-select from
diets varying in macronutrient composition, they will consume at
least30% of theirenergyfromprotein, thus inagreementwithour
hypothesis.Moreover,whilstmeanproteinintakeoverthecourseof
thestudy was37%,the energy consumptionalteredover thedura-
tionofthestudy,withanincreasefrom29%totalenergyonday1to
TABLE3 Linearandquadraticresponsestoanalysisoftotalenergyconsumed,gramsofmacronutrientsconsumed,specificoverall
macronutrientenergyintakeandratiosindogs(n=15)offeredhighprotein(PFC57.6:41.7:0.7%),highfat(PFC12.8:86.7:0.5%)orhigh
carbohydrate(PFC17.8:27.7:54.5%)dietsat500%maintenanceenergyrequirementsfor10days
Response Model αSE β1SEM β2SE
TotalEnergyConsumed(unit) Linear 373.10*** 40.42 −23.97*** 3.28 –
Quadratic 419.10*** 31.8 −60.00*** 8.78 3.43*** 0.78
Proteinintake(%ofoverallME) Linear 27.77*** 3.17 1.60** 0.36 –
Fatintake(%ofoverallME) Linear 69.95*** 3.14 −1.81*** 0.37 –
Carbohydrateintake(%of
overallME)
Linear 2.28*** 0.62 0.21 0.27 –
Protein(kcalsday−1) Linear 4,856.21*** 921.20 −70.00 96.95 – –
Fat(kcalsday−1) Linear 6,989.38*** 1,197.65 −607.24*** 124.10 –
Carbohydrate(kcalsday−1) Linear 284.09*** 64.12 −26.04** 8.33 –
Protein:Fat Ratio Linear 0.40*** 0.07 0.05*** 0.01 –
α, Intercept; SE, Standard error; β1,CoefficientofLinearterm;β2,CoefficientofQuadraticterm.
*p<.05.
**p < .01.
***p < .001.
FIGURE6 Meanself-selectedmacronutrienttotalenergy
intake(solidline)andlinearfittedresponse(dottedline)ofadult
dogs(n=15)(27.77±3.17protein%+1.60±0.36xDay),
(69.95±3.14fat%–1.81±0.37xDay),(2.28±0.62carbohydrate
%+0.21±0.27xDay),offeredhighprotein(PFC57:42:1%),
highfat(PFC13:86:1%)orhighcarbohydrate(PFC18:28:54%)
dietsfor10days.Protein(%energyintake)increased(p<.01)
andfatdecreased(p<.001)
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   ROBERTS ET al.
44%by day 10.Thisincrease in proteinintakewas associated with
a decrease in fat consumption over the experiment, with the dogs
consuming68% on day1and 52% by day10.Thus, the protein:fat
ratioincreasedfrom0.45onday1to0.90byday10.Althoughboth
proteinandfat intake altered significantly during the study, carbo-
hydrateconsumption remained steadyat3% throughout thestudy.
These changes in macronutrient selection by the dogs are illus-
tratedin Figures7a,b.Anutrition trianglewasutilised, to represent
a multidimensional assessment of dietary composition information
(Raubenheimer,2011). Collectively,thesechanges in macronutrient
intakeresultedinenergy consumptiondecreasingfrom of363%on
day1to162%onday10.
Based on raw data energy intake, the dogs selected an average
macronutrientP:F:C ratio of38:59:3%(byenergy) during the study.It
mustbe noted,however,thattheP:F:Cratio onday1(35:62:3byen-
ergy)wasdifferenttothat consumedon day10 (45:51:4% byenergy).
Thisdifferencewasdriven by the decreaseinfat energy consumption
(6,382–917kcalsday−1) ratherthan any drop in protein intake(4,786 
to4,156kcalsday−1)overthedurationofthestudy.Suchareductionin
energyconsumptionislikelyasaresultofincreasingbodyfatinthedogs
astheexperimentprogressed,withplasmaleptinlevelslikelytoberising
(Ishiokaetal., 2002).Asleptin serves asasignallingpathway between
adiposetissueandthecentralnervoussystem,theconsequenceofthis
maybeareductioninenergyintake(Akers&Denbow,2008).
The initial targeting of fat dense food sources has also been
demonstrated in the predatory beetle Agonum dorsale (Carabidae)
(Raubenheimer,Mayntz,Simpson,&Tøft,2007).Withinthestudy,the
beetleswereassessedinregardtotheirnutrientintakeover10days,
withthe first 2days involvingtargetinga diet rich in fatafterwhich
protein intake increased.Although this study involved determining
macronutrientintakeafteremergencefromhibernation,andthusdif-
feredfromourinvestigation,wedidobservethesamemacronutrient
pattern. Our dogsalso targeted a high fat diet initially, with energy
contributionfromproteinincreasingthereafter,whichmayindicatean
evolutionary past, whereby limited prey availability would predispose
dogstoinitiallyselectfatsources.Althoughthedogsusedinourstudy
were maintained at a healthy body condition score, variations in how
a score relates tobody fat content can occur (Ishioka etal., 2005).
Further studies in dogs investigatingthe association between body
composition,macronutrientselection,totalenergyintakeandfactors
suchas leptin involved in influencing food intake would help better
understandboththemacronutrientandenergyintakeofdogs.
WhencomparingtheaverageP:F:Cratioof38:59:3%selectedby
the dogs in our study to thatdetermined by Hewson-Hughes etal.
(2012)of30:63:7(%byenergy),severalkeyfactorscouldexplainthe
differences,namelythelengthofthe studyperiod, thecalculationof
theP:F:Candtheexperimentalstructure.
In Hewson-Hughes etal. (2012), the experienced phase was
7 days in duration, whereas in the present study, it was 10 days. In
thecurrentstudy,whenmacronutrientselectionwasexaminedacross
thestudy period,itwas apparentthat majordifferencesintheP:F:C
selected occurred during the latter stages of the study, averaging
47:49:4(%byenergy)ondays9and10.Thus,theshortertimeframe
inHewson-Hughesetal.(2012)mayhaveresultedinmissingthisap-
parentkeymacronutrienttransitionalperiod.Itislikelythatproviding
anaveragemacronutrientratioacrossthewholeofthe experimental
periodmayfailto interpret the true nutritional movementthe dogs
madeoverrelatively short testing periods (7–10days). Forexample,
the established average macronutrient ratio observed by Hewson-
Hughes etal. (2012) overa 7-dayperiod (30:63:7% by energy) was
similartotherawdataovertheinitial7daysofourstudy(36:61:3%by
energy).However,onlywhenaveragemacronutrientvaluesareteased
apartforeach dayand examined indetail,do these keytimeframes
becomeobvious.Themacronutrientselection bythedogswithin our
studyvariedsignificantlyoverthe10-dayperiod,withadecreaseinfat
intake(68%vs.52%byenergy)andincreasein protein(29%vs.44%
byenergy)observed.Itremainstobedeterminedifthemacronutrient
selectionbythedogshadstabilisedafter10days,orwhetherprotein
intakewouldcontinuetoincrease.
FIGURE7 (a,b)Macronutrienttotalenergyintakeofindividual
adultdogs(n=15)offeredhighprotein(P:F:C57:42:1%byenergy),
highfat(P:F:C13:86:1%byenergy)orhighcarbohydrate(P:F:C
18:28:54%byenergy)diets.Theyaxisofbothaandbrepresentsfat
intake,withthexaxissignifyingthecarbohydrateintake(byenergy).
Thegraphsdepictpartialcontourplotswithlinesrepresenting
proteinintake(alsocolourcodedwiththelegendshowingtherange
ofcolours).Percentageofmacronutrienttotalenergyintakevalues
foralldogsaresymbolisedbyreddots
    
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ROBERTS ET al.
Secondlythe experimental structure oftheHewson-Hughesetal.
(2012) study involvedthree distinct phases, of differing duration and
feedingpatterns.Theseconsistedofnaïveself-selection(havingaccess
toall threemealoptions simultaneouslyfor7days),learning (eight,3-
dayperiods,wherebythedogswererestrictedtoaspecificdiet(HC,HF,
HP)for adayof eachperiod)andexperienced (thesameasthenaïve
phase). Thus, the potential exists whereby within the self-selective
phases,thefeedingperiodendedjustasthedogswerestartingtoreg-
ulatetheirmacronutrientintake.Inbetweenthesephases,thelearning
stagemayalsohaveconfuseddogs alreadystartingto targeta macro-
nutrientintake,thatisbyconfiningeachtoa specificdietfor24hours
andrepeatingthe process eight times. Therefore,thecombination of
ashorterstudyperiod, and the inclusion ofa learningphase, limiting
thedogstospecificdietsinHewson-Hughesetal.(2012)mayhaveaf-
fectedthedog’sabilitytotargetthemacronutrientintakeweobserved.
RomsosandFerguson(1983)also addressedmacronutrientselec-
tioninthedomesticdog;however,theirprimaryaimwastounderstand
theregulationofproteinintake.Ina4-weekstudy,twodifferentsetsof
dietswereofferedtothedogs,differingnotjustinproteincontent,but
also in fat and carbohydrate. Whilst the results showed the animals se-
lected30%oftheirmetabolisableenergyfromprotein,limitationsinre-
gardtonutrientmovement,primarilyduetothecarbohydratecontent
varyingfrom 20% to 42% MEwithin the test diets,could potentially
havemaskedthetruemacronutrientratiothedogswishedtoselect.
The self- selected macronutrient profile has also been reported for
the domestic cat (Felis catus)usinganapproachsimilartothatapplied
tothe domestic dog. Hewson-Hughes etal. (2011), establishedthat
macronutrient energyprofile (P:F:C) was 52:36:12 (% byenergy). In
additionthe study also suggests that cats havea carbohydrateceil-
ingof 300kJday−1, which constrains them to deficits in protein and
fat(relativetothe determined intaketarget)when restrictedto high
carbohydrate diets (Hewson-Hughes etal., 2011). Aswith the dog
study,alackofreportingrelatingtomacronutrientintakeoverthedu-
rationof theprojectwas apparent.However,usinganother member
ofthefelidfamilythemink (Mustela vison), it was demonstrated that
withinthefirst24hrofbeingallowedtoself-selectaP:F:C(withcar-
bohydratefixedat15%)froma numberofcomplementaryfoods,the
minkselectedadietconsistingof(P:F)of35:50(%byenergy)(Mayntz
etal., 2009). This ratiowas observed throughout the 11-day study,
with additionally when confined to diets that did not allow the desired
protein:fat ratio to be achieved, the closet possible to that previously
establishedbeingtargeted.
Inthecurrentstudy,itisevidentthatoverthe10-dayexperimen-
talperiod,thedogsmadeadietary“switch,”reducingfatandincreas-
ingproteinintakeonanenergybasis.Tobetterunderstandthedietary
switch,thefeedingdynamicsofthedietswereexplored.
Whentheoverallpercentageofdogswhichfirstapproachedand
firstconsumeda givendiet was determined (Figure3), itwasclear
thattheHFdietdisplayedsimilarvaluesof29%and31%,thusindi-
catingmost ofthe dogswhich approachedthediet first,consumed
someofit.However,whentheHPdietwasexamined,47%ofdogs
approachedit first, with 64% then consuming some ofitfirst.This
differencecanbeexplainedbyresultsfromtheHCdiet,which24%
ofdogsapproachedfirst;however,only4%thenconsumedany.The
majorityofthedogswhichapproachedtheHCdietdecidedtomove
awayandconsumeatleastsomeoftheHPdietinstead.Throughout
the study,the percentage of times that each diet was approached
andconsumed remainedconsistent.Thishighlightedthat theinitial
decisionto consumeaspecific diet atthestart oftheinvestigation
wasmaintainedduringthestudy.Inaddition,thedataalsoshowthat
theHCdietwasmuchmostlikelytoremainuntasted(58%),thanthe
HFand HPdiets(20%and 3% respectively)(Figure4).Collectively,
these feeding dynamics may indicate that therewas an olfactory
differencebetween the diets. As with the percentage of diets first
approached and consumed, the proportion of each diet completely
avoided were similar over the duration of the study. This would in-
dicatethe preferenceofdogstotarget oravoidspecific diets from
day1oftheinvestigation,remainedconsistentoverthesubsequent
9 days.
Indeed whilst we did not attempt to ensure palatability of our
diets were consistent (e.g., with the use of a palatant), the same
key ingredientswere used in all the diets, just in different propor-
tions. Interestingly research conducted by Salaun, Le Paih, Roberti,
Niceron, and Blanchard (2016) foundthat whilst the application of
a palatability enhancerincreased food intake in domestic cats, they
werestill capable of macronutrient regulationwhenofferedpairs of
differingdiets. Moreover,a recent study has also indicated thatthe
domestic cat is able to detect and maintain a macronutrient prefer-
ence,despitechangesinflavour(Hewson-Hughes,Colyer,Simpson,&
Raubenheimer,2016),withcatsstillpreferringadietcontainingapro-
tein:fatratioof70:30(byenergy),evenwhenthe dietwas flavoured
with(apparently)negativeflavours.
Inthecurrentstudy,lambgreentripewasusedastheingredientto
manipulatethedietaryproteincontent.Whilstthedogsmigratedover
thecourseofthestudytoamacronutrientratiowithagreaterenergy
contributionfromprotein,itmaybearguedthatthisindicatedapref-
erenceforgreentripe,ratherthanadesireforproteinper say.Asimilar
argumentcouldalsoberaisedregardingthecarbohydratesourceused
throughout the experiment (maize). Evidently carbohydrates played
aminimal roleinregard toselecteddietary compositioninthe dogs;
however, it is possible that this specific carbohydrate source was dis-
likedmoresothanothersthatarealsotypicallyusedindogfoods(e.g.,
rice orbarley). Future studies could addressthese questions, where
dogsareoffereddietsofsimilarmacronutrientratios,usingdifferent
protein, fat or carbohydrate sources. Similarly, moisture content was
notconsistentbetween diets in thecurrent study, with the HC diet
havinglessmoisturethantheHPdiet.Atpresent,itisunknownifthis
had any impact on the resulting macronutrient profile, but studies
have indicatedin cats that energy intake and food consumption re-
duceasthelevelofwaterinadietincreases(Wei,Fascetti,Villaverde,
Wong,&Ramsey,2011).
In conclusion, the study clearly demonstrated that over a ten- day
experiment, the test dogs selected a diet dominated by consump-
tionofenergy derived primarily from fat and protein,withcarbohy-
drateplaying a minimal role in contributing to overall energyintake.
However, only after the completion of much deeper investigations
8 
|
   ROBERTS ET al.
into the selective capabilities and mechanisms influencing these di-
etarydecisions,willwetrulyhaveagrasponwhatitisundoubtedlya
fascinatingandhighlycomplexareaofstudy.
ACKNOWLEDGEMENTS
We thank the staff at the Massey University Canine Nutrition Unit
fortheirhelpinconductingthestudy.ThisprojectwasfundedbyK9
Natural,AgResearchCore Funding(A21247) andAgmardt (A15013).
MrMarkRobertsissupportedbyaMasseyUniversityPhDscholarship.
ORCID
M. T. Roberts http://orcid.org/0000-0001-8057-2065
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SUPPORTING INFORMATION
Additional Supporting Informationmay be found online in the sup-
portinginformationtabforthisarticle.
How to cite this article:RobertsMT,BerminghamEN,Cave
NJ,YoungW,McKenzieCM,ThomasDG.Macronutrient
intakeofdogs,self-selectingdietsvaryingincomposition
offered ad libitum. J Anim Physiol Anim Nutr. 2017;00:1–8.
https://doi.org/10.1111/jpn.12794
... The KD macronutrient profile differs remarkably from the RMBD profile. In terms of percent dry matter, a KD usually consists of a "protein:fat:carbohydrate" (PFC) macronutrient ratio 16-38%:6-18%:40-60%, whereas the PFC ratio of RMBD is typically %45:50%:0-10% (17). ...
... A couple of studies looking at macronutrient preference among dogs served several food choices of varying macronutrient compositions ad libitum have indicated that several breeds of dogs are well-attuned to what they prefer and what their bodies require (17,118). In the first study, the authors observed that several breeds of dogs adjusted to a preferred PFC macronutrient composition of 30%:63%:7% ME over a 7-day period (118), and another study observed that Harrier hound dogs adjusted to a PFC macronutrient ratio of 44%:52%:4% ME (17). ...
... A couple of studies looking at macronutrient preference among dogs served several food choices of varying macronutrient compositions ad libitum have indicated that several breeds of dogs are well-attuned to what they prefer and what their bodies require (17,118). In the first study, the authors observed that several breeds of dogs adjusted to a preferred PFC macronutrient composition of 30%:63%:7% ME over a 7-day period (118), and another study observed that Harrier hound dogs adjusted to a PFC macronutrient ratio of 44%:52%:4% ME (17). The adequacy of diets for domesticated dogs, especially with regard to macronutrient composition, has been studied by comparing their diet with the diet of wolf (Canis lupus) populations (119). ...
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... En estudios realizados donde se mide el consumo voluntario de perros y gatos, informan de la proporción de la energía según el origen de esta, que permite optimizar el consumo de materia seca de forma voluntaria, en el caso de perros esta relación de proteína:grasa:carbohidratos es de 38:59:3 y en gatos es de 52:36:12 (Roberts et al., 2018), valores diferentes a los calculados para los alimentos para perros (26,43:32,33:41:24) y gatos (31,62:36,72:31,66) con registro activo en el país durante la evaluación, donde los alimentos evaluados, en promedio recargan el aporte energético en los alimentos en las fuentes de origen vegetal. ...
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... diets (Romsos and Ferguson, 1983;Hewson-Hughes et al, 2012;Roberts et al, 2017), raising the possibility that dogs fed modern commercial diets, low in protein, and high in carbohydrate and additives, might face physiological and metabolic challenges (Hill, 2010;Bosch et al, 2015). Furthermore, a wolf 's diet would be expected to provide a very different substrate for the intestinal microbiota, compared to both dry and moist commercial dog foods . ...
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Dogs are uniquely associated with human dispersal and bring transformational insight into the domestication process. Dingoes represent an intriguing case within canine evolution being geographically isolated for thousands of years. Here, we present a high-quality de novo assembly of a pure dingo (CanFam_DDS). We identified large chromosomal differences relative to the current dog reference (CanFam3.1) and confirmed no expanded pancreatic amylase gene as found in breed dogs. Phylogenetic analyses using variant pairwise matrices show that the dingo is distinct from five breed dogs with 100% bootstrap support when using Greenland wolf as the outgroup. Functionally, we observe differences in methylation patterns between the dingo and German shepherd dog genomes and differences in serum biochemistry and microbiome makeup. Our results suggest that distinct demographic and environmental conditions have shaped the dingo genome. In contrast, artificial human selection has likely shaped the genomes of domestic breed dogs after divergence from the dingo.
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Why do dogs behave in the ways that they do? Why did our ancestors tame wolves? How have we ended up with so many breeds of dog, and how can we understand their role in contemporary human society? Explore the answers to these questions and many more in this study of the domestic dog. Building on the strengths of the first edition, this much-anticipated update incorporates two decades of new evidence and discoveries on dog evolution, behavior, training, and human interaction. It includes seven entirely new chapters covering topics such as behavioral modification and training, dog population management, the molecular evidence for dog domestication, canine behavioral genetics, cognition, and the impact of free-roaming dogs on wildlife conservation. It is an ideal volume for anyone interested in dogs and their evolution, behavior and ever-changing roles in society. The ultimate book about the domestic dog, ideal for anyone interested in their evolution, behavior and ever-changing roles in society A new edition of a classic text, presenting the latest research on dog behavior, training, domestication, genetics and cognition Includes seven entirely new chapters by leading experts in the field, incorporating two decades of new evidence and discoveries.
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Domestic dogs diverged from grey wolves between 13 000 and 17 000 years ago when food waste from human settlements provided a new niche. Compared to the carnivorous cat, modern-day dogs differ in several digestive and metabolic traits that appear to be more associated with omnivorous such as man, pigs and rats. This has led to the classification of dogs as omnivores, but the origin of these ‘omnivorous’ traits has, hitherto, been left unexplained. We discuss the foraging ecology of wild wolves and calculate the nutrient profiles of fifty diets reported in the literature. Data on the feeding ecology of wolves indicate that wolves are true carnivores consuming a negligible amount of vegetal matter. Wolves can experience prolonged times of famine during low prey availability while, after a successful hunt, the intake of foods and nutrients can be excessive. As a result of a ‘feast and famine’ lifestyle, wolves need to cope with a highly variable nutrient intake requiring an adaptable metabolism, which is still functional in our modern-day dogs. The nutritive characteristics of commercial foods differ in several aspects from the dog’s closest free-living ancestor in terms of dietary nutrient profile and this may pose physiological and metabolic challenges. The present study provides new insights into dog nutrition and contributes to the ongoing optimisation of foods for pet dogs.
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A recent area of progress in nutritional ecology is a growing awareness that nutritional phenotypes are best understood in a multidimensional context, where foraging is viewed as a process of balancing the intake and use of multiple nutrients to satisfy complex and dynamic nutrient needs. Numerous laboratory studies have shown that this view can yield novel insights into unresolved questions and provide a framework for generating new hypotheses. By contrast, progress with this multidimensional view has been slow in the arena of ultimate interest to functional biologists, the field. One reason for this is that the Geometric Framework for nutrition that has been extensively used in laboratory experiments focuses on amounts of nutrients (e.g., required, eaten, or retained), and such data are typically very difficult or impossible to collect for most free-ranging animals. Further, many problems in field-based nutritional ecology involve comparisons of mixtures that are expressed as proportions (e.g., food, diet, body, or fecal compositions), rather than absolute amounts. As yet, however, no geometric framework has been established in nutritional ecology for this. Here I recommend an approach for the geometric analysis of nutritional mixtures, and illustrate its use in a variety of contexts by reanalyzing published data. Despite its simplicity, this approach holds considerable promise for furthering the study of field-based nutritional ecology.
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Cats are obligate carnivores adapted to high-protein diets, but are commonly fed diets rich in carbohydrate. The aim of this study was to examine the food intake choices of cats when diets with different protein and carbohydrate contents were offered. Thirty-nine cats participated in voluntary dietary intake studies. Four foods were formulated to provide between 24% and 53% of metabolizable energy as protein, between 43% and 11% as carbohydrate and holding dietary fat constant with a contribution of approximately 36%. Foods were offered either singly to evaluate voluntary food intake or in pairs to compare food intake between pairs of diets. Cats regulated their macronutrient intake to attain an overall diet composition that provided 53% of metabolizable energy as protein, 11% as carbohydrate and 36% as fat. The protein contribution corresponded to approximately 6 g of protein/kg body weight/day. High-protein/low-carbohydrate diets were always eaten preferentially over low-protein/high-carbohydrate foods. When low-protein/high-carbohydrate diets were offered, cats limited their food intake to limit daily carbohydrate intake to less than 3 g of carbohydrate/kg body weight. This carbohydrate ceiling may limit protein and even energy intake when only low-protein/high-carbohydrate diets were offered. The inclusion of palatability enhancer in the diets increased food intake but did not change protein or carbohydrate intake patterns, indicating that macronutrient intake can be regulated regardless of the use of palatability enhancers in cats. We conclude that cats can discriminate between diets based on macronutrient composition and regulate their intake to maintain maximal protein intake but limit carbohydrate intake.
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Obesity is defined as an accumulation of excessive amounts of adipose tissue in the body, and is the most common nutritional disorder in companion animals. Obesity is usually the result of either excessive dietary intake or inadequate energy utilization, which causes a state of positive energy balance. Numerous factors may predispose an individual to obesity including genetics, the amount of physical activity, and the energy content of the diet. The main medical concern of obesity relates to the many disease associations that accompany the adiposity. Numerous studies demonstrated that obesity can have detrimental effects on the health and longevity of dogs and cats. The problems to which obese companion animals may be predisposed include orthopedic disease, diabetes mellitus, abnormalities in circulating lipid profiles, cardiorespiratory disease, urinary disorders, reproductive disorders, neoplasia (mammary tumors, transitional cell carcinoma), dermatological diseases, and anesthetic complications. The main therapeutic options for obesity in companion animals include dietary management and increasing physical activity. Although no pharmaceutical compounds are yet licensed for weight loss in dogs and cats, it is envisaged that such agents will be available in the future. Dietary therapy forms the cornerstone of weight management in dogs and cats, but increasing exercise and behavioral management form useful adjuncts. There is a need to increase the awareness of companion animal obesity as a serious medical concern within the veterinary profession.
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Objective: To develop morphometric equations for prediction of body composition and create a body fat index (BFI) to estimate body fat percentage in overweight and obese dogs. Design: Prospective evaluation study. Animals: 83 overweight or obese dogs ≥ 1 year of age. Procedures: Body condition score (BCS) was assessed on a 5-point scale, morphometric measurements were made, and visual and palpation-based assessments and dual-energy x-ray absorptiometry (DEXA) were performed. Equations for predicting lean body mass, fat mass, and body fat as a percentage of total body weight (ie, body fat percentage) on the basis of morphometric measurements were generated with best-fit statistical models. Visual and palpation-based descriptors were used to develop a BFI. Predicted values for body composition components were compared with DEXA-measured values. Results: For the study population, the developed morphometric equations accounted for 98% of the variation in lean body mass and fat mass and 82% of the variation in body fat percentage. The proportion of dogs with predicted values within 10% of the DEXA values was 66 of 83 (80%) for lean body mass, 56 of 83 (68%) for fat mass, and 56 of 83 (67%) for body fat percentage. The BFI accurately predicted body fat percentage in 25 of 47 (53%) dogs, whereas the value predicted with BCS was accurate in 6 of 47 (13%) dogs. Conclusions and clinical relevance: Morphometric measurements and the BFI appeared to be more accurate than the 5-point BCS method for estimation of body fat percentage in overweight and obese dogs. Further research is needed to assess the applicability of these findings to other populations of dogs.