Effects of weight loss on the cardiac parameters of obese dogs

Abstract

Pereira-Neto G. B., Brunetto M. A., Sousa M. G., Carciofi A. C. & Camacho A. A. 2010. Effects of weight loss on the cardiac parameters of obese dogs. Pesquisa Veterinaria Brasileira 30(2): 167-171. Setor de Clinica Medica Veterinaria, Faculdade de Ciencias Agrarias e Veterinarias, Universidade Estadual Paulista, Jaboticabal, SP 14884-900, Brazil. E-mail: glaucia.vet@gmail.com Obesity is one of the most frequent nutritional problems in companion animals and can lead to severe health problems in dogs and cats, such as cardiovascular diseases. This research aimed to evaluate the structural and functional cardiac changes after weight loss in obese dogs. Eighteen obese healthy dogs were assigned into three different groups, according with their initial body weight: Group I (dogs up to 15 kg), Group II (dogs weighing between 15.1 and 30 kg), and Group III (dogs weighing over 30 kg). The animals were submitted to a caloric restriction weight-loss program until they lose 15% of the body weight. The M-mode echocardiogram, electrocardiogram, and blood pressure evaluations were performed before the diet has started and after the dogs have reached the target weight. Data showed a decrease in left ventricular free wall thickness during diastole and systole in Group III, decrease in the systolic blood pressure in Group III, and also in the mean blood pressure in Group II. It was possible to conclude that the weight loss program can reverse structural cardiac changes such as left ventricle eccentric hypertrophy in dogs weighing more than 30 kg, and decrease the arterial blood pressure in obese dogs.

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Pesq. Vet. Bras. 30(2):167-171, fevereiro 2010
RESUMO.- [Efeitos da perda de peso sobre os parâ-
metros cardíacos em cães obesos.] A obesidade é uma
das doenças nutricionais mais frequentemente observa-
da em cães e pode provocar sérios problemas de saúde,
como os distúrbios cardiovasculares. Realizou-se este
estudo visando avaliar algumas das possíveis alterações
estruturais e funcionais cardíacas decorrentes da corre-
ção da obesidade canina. Para isso foram utilizados 18
cães obesos divididos pelo peso corporal em Grupo I (até
15kg), Grupo II (entre 15,1 e 30 kg) e Grupo III (acima de
30 kg). Os animais foram submetidos à restrição calórica
de forma a perderem 15% do peso vivo. Foram realiza-
dos os exames ecocardiográfico em modo-M, eletrocar-
diográfico e mensuração da pressão arterial dos animais
antes do início do tratamento da obesidade e após atingi-
rem o peso meta. Os resultados revelaram que após a
redução de peso ocorreram diminuições significativas da
espessura da parede livre do ventrículo esquerdo duran-
te a sístole e diástole no Grupo III, diminuição da pressão
arterial sistólica no Grupo III e também da pressão arteri-
al média no Grupo II. Assim, concluiu-se que a perda de
peso pode reverter as alterações estruturais cardíacas,
como a hipertrofia excêntrica do ventrículo esquerdo em
cães obesos acima de 30 kg, como também reduzir a pres-
são arterial sistêmica em cães obesos submetidos à res-
trição calórica mediante administração de dieta hipocaló-
rica.
TERMOS DE INDEXAÇÃO: Ecocardiografia, eletrocardiografia,
pressão arterial, obesidade, cães.
INTRODUCTION
Obesity is an important condition that has been a point of
concern worldwide and it is considered the main public
Effects of weight loss on the cardiac parameters of obese dogs1
Gláucia B.P. Neto2*, Márcio A. Brunetto2, Marlos G. Sousa2, Aulus C. Carciofi3
and Aparecido A. Camacho3
ABSTRACT.- Pereira-Neto G.B., Brunetto M.A., Sousa M.G., Carciofi A.C. & Camacho
A.A. 2010. Effects of weight loss on the cardiac parameters of obese dogs. Pesquisa
Veterinária Brasileira 30(2):167-171. Setor de Clínica Médica Veterinária, Faculdade de
Ciências Agrárias e Veterinárias, Universidade Estadual Paulista, Jaboticabal, SP 14884-
900, Brazil. E-mail: glaucia.vet@gmail.com
Obesity is one of the most frequent nutritional problems in companion animals and can
lead to severe health problems in dogs and cats, such as cardiovascular diseases. This
research aimed to evaluate the structural and functional cardiac changes after weight loss
in obese dogs. Eighteen obese healthy dogs were assigned into three different groups,
according with their initial body weight: Group I (dogs up to 15 kg), Group II (dogs weighing
between 15.1 and 30 kg), and Group III (dogs weighing over 30 kg). The animals were
submitted to a caloric restriction weight-loss program until they lose 15% of the body weight.
The M-mode echocardiogram, electrocardiogram, and blood pressure evaluations were
performed before the diet has started and after the dogs have reached the target weight.
Data showed a decrease in left ventricular free wall thickness during diastole and systole in
Group III, decrease in the systolic blood pressure in Group III, and also in the mean blood
pressure in Group II. It was possible to conclude that the weight loss program can reverse
structural cardiac changes such as left ventricle eccentric hypertrophy in dogs weighing
more than 30 kg, and decrease the arterial blood pressure in obese dogs.
INDEX TERMS: Echocardiography, electrocardiography, arterial blood pressure, obesity, dogs.
1 Received on September 8, 2009.
Accepted for publication on January 7, 2010.
2 Postgraduate student, Departamento de Clínica e Cirurgia Veteriná-
ria, Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universida-
de Estadual Paulista (Unesp), Via de acesso Prof. Paulo Donato
Castellane s/n, Jaboticabal, SP 14884-900, Brazil. *Autor para corres-
pondência: glaucia.vet@gmail.com
3 Departamento de Clínica e Cirurgia Veterinária, FCAV, Unesp, Ja-
boticabal, SP.

Pesq. Vet. Bras. 30(2):167-171, fevereiro 2010
Gláucia B.P. Neto et al.
168
health problem in modern society. In recent years, a great
number of obesity in companion animals has been observed.
Epidemiological surveys performed in clinics and veterinary
hospitals estimate the prevalence of canine obesity
between 25-35% (Greco 2002). Therefore, it is believed
that sedentary lifestyles, which have become the norm
rather than exception for many dogs, as well the supply of
flavourful, hypercaloric foods, contribute to energy imba-
lances that lead to excess weight (Burkholder & Toll 2000,
Markwell & Edney 2000).
The obese dog is in great risk of developing chronic
health problems including respiratory, cardiovascular, and
osteoarticular disturbances. It can also develop hyper-
insulinemia, glucose intolerance, exercise and heat into-
lerance and reduced physical disposition (Case et al. 1998,
Markwell & Edney 2000, Lund et al. 2006, German 2006).
Due to a lack of information on this issue in animals,
cardiovascular problems related to obesity in humans are
frequently extrapolated to dogs (Atkins 1999). Obesity is
a volume expansion illness with high cardiac output,
increased plasma and extracellular fluid, neuro-humoral
activation, reduced urinary excretion of sodium and water,
increased heart rate, elevated arterial pressure, systolic
and diastolic ventricular dysfunction, and exercise
intolerance (Atkins 1999, Alpert 2001a). Reduction in body
weight is capable of reversing the structural and hemo-
dynamic abnormalities associated with human obesity,
decreasing left ventricular mass and improving diastolic
ventricular filling in patients who have ventricular hyper-
trophy prior to weight loss. Furthermore, in patients with
obesity-associated congestive cardiac failure, reduction
of body weight may revert some of the clinical manifes-
tations decurrent of cardiac changes (Alpert 2001b, Uwaifo
et al. 2003).
Studies performed in dogs have demonstrated that
weight gain in animals submitted to a hypercaloric diet
was associated with an increase in heart rate, cardiac
output, arterial pressure, plasma volume and fasting
insulin; the rise of these parameters is related directly to
body weight gain. At the end of the weight loss program it
was observed that the analyzed variables gradually
returned to their basal values (Rocchini et al. 1987).
The purpose of the study reported herein was to
investigate possible structural and functional cardiac
changes in dogs submitted to obesity correction.
MATERIALS AND METHODS
Animals. Eighteen privately owned obese dogs were divided
into three groups based on animal body weight. Group I (GI):
obese dogs with body weight up to 15 kg (n=6). This group was
composed of 6 females (5-10 years old), including one Beagle,
one Dachshund, one Fox Terrier and three mongrels. Group II
(GII): obese dogs with body weight between 15-30 kg (n=6).
This group comprised 5 females and 1 male (3-11 years old),
including one American Pit Bull, one English Cocker Spaniel,
and four mongrels. Group III (GIII): obese dogs with body weight
above 30 kg (n=6). This group comprised 3 males and 3 females
(5-11 years old), including one German Shepherd dog, one
Brazilian Mastiff, and four mongrels. All animals were submitted
to four exams: physical, hematological (including hemogram and
serum dosages of alanine aminotransferase, alkaline phos-
phatase, creatinine, urea, total protein, albumin, cholesterol,
triglycerides, and fasting glucose), electrocardiograph, and
echocardiograph. Obese individuals with results within normal
parameters in physical and haematological tests and without
congenital or acquired cardiac disease participated in the
experiment. Consequently, only obese animals ingesting
excessive high caloric food were accepted. Obesity was
diagnosed based on body inspection and direct palpation. Dogs
were classified according to their body condition score (BCS)
using a 9-point system, in which animals that presented scores
of 8 and above were considered obese (Laflamme et al. 1997).
The study protocol was reviewed and approved by an animal
care committee of Sao Paulo State University (process number
016914).
Weight loss protocol. All dogs were submitted to a weight
reduction program in which they were fed 60% of their
maintenance energy requirements (NRC 2006), calculated by
their estimated target weight (TW). TW was considered as actual
weight (AW) less 15% (TW = AW - 15% AW). A specific
commercial hypocaloric diet4 was administered until TW was
attained. Caloric restriction (CR) was calculated as 80 x TW
(kg)0.75 Kcal of metabolizable energy per day. Weight reduction
protocol also included dividing the volume of daily food into at
least three meals.
Echocardiography. A complete routine transthoracic
echocardiographic examination was performed in each dog with
an echocardiograph5 and a 5.0-7.5 MHz mechanical sector
transducer. Echocardiographic images were recorded on
videotape with a simultaneous lead II electrocardiogram for
offline measurements by using the measurement software in
the echocardiographic recorder. Hair was clipped between the
right 3rd and 6th intercostal spaces, and left 2nd and 7th intercostal
spaces. Generous coupling gel was applied to these areas of
the thorax immediately before echocardiography was started.
Measurements were taken by using two-dimensional-guided M-
mode on the standard right parasternal long-axis view at aortic
valve level for measurement of left atrial (LA) and aortic diameter
(AO); at chordae tendineae level for measurement of left
ventricular end-systolic (LVESD) and end-diastolic (LVEDD)
dimensions, interventricular septal thickness in systole (IVSS)
and diastole (IVSD), left ventricular free wall thickness in systole
(LVWS) and diastole (LVWD). Such values were used for
calculation of the left atrium-to-aorta ratio (LA/AO), ejection
fraction (%EF), and fractional shortening (%FS); and at mitral
valve level for measurement of E-point to septal separation
(EPSS). Heart rate was also calculated based on RR interval
determined from simultaneous lead II electrocardiogram
(Kittleson & Kienle 1998).
Electrocardiography. A 6-lead computerized electro-
cardiogram6 was used for the electrocardiography recording.
Dogs were positioned in right lateral recumbency and the
electrode clips were attached to the animal’s skin in the standard
positions as described by Tilley (1995). The paper speed was
50mm/sec and the electrocardiogram was standardized at 1mV
= 1cm. The electrocardiogram analysis was obtained from lead
4 Obesity Canine, Royal Canin.
5 Pandion S300, PieMedical, Maastricht, The Netherlands.
6 ECG-PC, TEB, São Paulo, Brazil.

Pesq. Vet. Bras. 30(2):167-171, fevereiro 2010
Effects of weight loss on the cardiac parameters of obese dogs 169
II. We measured the following parameters: duration of P wave
(Pms), P wave amplitude (PmV), duration of PR interval (PRms),
duration of QRS complex (QRSms), R wave amplitude (RmV),
duration of QT interval (QTms), ST segment amplitude (ST), T
wave amplitude (T), mean electrical axis, heart rate (HR) and
heart rhythm.
Non-invasive arterial pressure evaluation. Non-invasive
arterial pressure measurements were obtained from all dogs.
Dogs were gently restrained in a lateral recumbency for
examination. An oscillometric monitor7 was used to obtain
measurements with appropriate sized cuff (inflatable bladder
width 0.4 times the circumference of limb at measurement site)
(Brown et al. 2007). Five consecutive readings were obtained
from systolic (SAP), mean (MAP) and diastolic (DAP) arterial
blood pressure, the lowest and highest values were discarded
and the remaining three averaged.
Statistical analysis. Echocardiographic and electro-
cardiographic evaluations and measurements of systolic, mean
and diastolic arterial pressure and body weight were done before
initiating therapeutic weight reduction protocol (Tbefore), and after
the dog had attained its target weight (Tafter). Variables analysed
at Tbefore and Tafter were compared, observing for alterations
resulting from weight reduction. The data was then evaluated
using an analysis of variance (ANOVA). The means of dependant
variables studied at the two experimental times (Tbefore and Tafter)
were compared for dogs within the same group. Data are given
as mean ± SD.
Tukey’s Studentized Range test was applied to compare the
means of Groups I, II and III, with the level of significance at 5%.
For all analysis, it was used a statistical software (Schlotzhauer
& Little 1997).
RESULTS
All dogs demonstrated consistent weight loss and reached
the target weight stipulated by the therapeutic protocol (a
minimum 15% reduction from initial body weight). Analysis
of the three groups separately revealed that Group I
presented 19.4% mean weight loss, Group II, 19.3%, and
Group III, 15.4%; similar weight loss percentage between
groups (Table 1). With restricting calorie intake to 60% of
maintenance energy requirements, it has observed weekly
weight loss percentage of 1.64%, 1.07% and 0.69% for
Groups I, II and III, respectively.
In regards to the echocardiographic data collected in
the present research (Table 2), after weight loss a significant
reduction was observed in systolic and diastolic left
ventricular free wall thickness only in Group III (p<0.05).
Percentage reductions in LVWS and LVWD for Group III
were 19.08% versus 13.6%, respectively.
Heart rate, left ventricle diameters, aorta and left atrium
diameters and their interaction, mitral valve E-point to
septal separation, interventricular septal thickness, ejection,
and shortening fractions did not show significant variations
in any of the groups after weight loss (p>0.05). However,
some of these parameters that depend on weight (AO,
LA, LVED, IVS and LVW) show significant differences
among Groups I, II, and III (p<0.05).
During the evaluation of electrocardiograms it was not
observed significant alterations of all electrocardiographic
variables studied (Table 3). However, P wave duration in
all dogs from Group III, 20% from Group I and 40% from
Group II was above normal values for the canine species
and body weight. After reaching their target weight, P wave
durations for these animals returned to reference values.
A significant decrease in arterial pressure was seen in
all dogs after weight reduction (Table 4). It was verified that
Table 2. Mean values and standard deviation of M-mode echocardiographic parameters
obtained from obese dogs of Groups I, II and III (each group, n=6), before and after weight loss
Group I Group II Group III
Before After Before After Before After
LVESD 1.76±0.22Aa 1.63±0.37Aa 2.37±0.36Ba 2.37±0.23Ba 2.65±0.38Ca 2.92±0.37Ca
LVEDD 2.77±0.50Aa 2.71±0.47Aa 3.66±0.62Ba 3.59±0.32Ba 4.24±0.57Ca 4.38±0.55Ca
IVSS 0.96±0.24Aa 1.06±0.12Aa 1.14±0.17Aa 1.27±0.17Aa 1.54±0.27Ba 1.52±0.14Ba
IVSD 0.72±0.06Aa 0.75±0.12Aa 0.86±0.27Aa 0.89±0.17Aa 1.08±0.26Ba 1.06±0.11Ba
LVWS 1.07±0.14Aa 0.96±0.09Aa 1.38±0.26Ba 1.23±0.32Ba 1.52±0.41Ba 1.23±0.30Bb
LVWD 0.80±0.07Aa 0.73±0.05Aa 0.93±0.10Ba 0.83±0.13Ba 1.07±0.17Ba 0.84±0.24Bb
%EF 66.80±7.36 Aa 72.20±9.52 Aa 65.40±2.97 Aa 63.20±7.76 Aa 67.80±4.82 Aa 62.00±5.29 Aa
%FS 36.00±5.96 Aa 40.20±7.76 Aa 34.80±2.59 Aa 33.60±5.86 Aa 37.60±3.65 Aa 33.20±4.14 Aa
AO 1.60±0.21Aa 1.57±0.15Aa 2.06±0.30Ba 1.96±0.17Ba 2.56±0.50Ca 2.58±0.41Ca
LA 1.75±0.16Aa 1.82±0.24Aa 2.17±0.30Ba 2.04±0.09Ba 2.64±0.42Ca 2.75±0.29Ca
LA/AO 1.10±0.12Aa 1.16±0.11Ab 1.06±0.06Ba 1.04±0.04Ba 1.04±0.08Ba 1.07±0.08Ba
SSPE 0.34±0.15A0.26±0.16Aa 0.31±0.09Aa 0.28±0.09Aa 0.37±0.13Aa 0.28±0.19Aa
A, B, C = means in the same line with different capital letters indicate statistical significance (p<0.05) among Groups I,
II and III.
a, b = means in the same line with different small letters indicate statistical significance (p<0.05) between before and
after times.
Table 1. Percentage of weight loss of dogs from Groups I,
II and III (each group, n=6), during weight loss program
Grupo 0 30 60 90 120 150 180 210
GI 0 6.87% 13.98% 16.34% 19.47% - - -
GII 0 6.43% 9.57% 12.88% 17.95% 19.35% - -
GIII 0 4.70% 6.45% 9.67% 12.05% 13.72% 15.09% 15.46%
0 = percentage of initial weight loss; 30, 60, 90, 120, 150, 180 e 210 =
percentages of weight loss after 30, 60, 90, 120, 150, 180 and 210
days on hypocaloric diet, respectively.
7 DX 2710 - DIXTAL non-invasive pressure.

Pesq. Vet. Bras. 30(2):167-171, fevereiro 2010
Gláucia B.P. Neto et al.
170
the decrease was significant for SAP in Group III (p=0.0479)
and for MAP in Group II (p=0.0499). Arterial pressure
decrease for Groups I, II and III were, respectively, 11.94%,
4.20% and 8.86% for SAP; 11.34%, 17.86% and 8.93% for
MAP, and 17.07%, 18.89% and 14.44% for DAP.
DISCUSSION
The caloric restriction adopted by this research was 60% of
the maintenance energy requirement of each animal. As a
result, each group satisfactorily attained the stipulated target
weight, with mean weekly loss in agreement with others
authors (Laflamme et al. 1997). Mean weight loss rate is
directly related to the degree of caloric restriction. In dogs,
restricting calorie intake to 50, 60 or 75% of maintenance
energy requirements can generate weekly weight loss
ranging from less to 1% to greater than 4%. This consi-
derable variation can be explained by individual animal
differences (Laflamme et al. 1997). On the other hand, lower
percentage weight losses result in better chances of
maintaining post-diet weight (Laflamme & Kuhlman 2002).
According to what was observed in this research, a minimum
weekly weight reduction must be 0.5% in order to keep the
animal’s owner interested and disposed to complete the
weight reduction program within a reasonable period
(Burkholder & Bauer 1998, Burkholder & Toll 2000).
Basal values for LVWS and LVWD were found to be
higher in all groups than values cited as normal by the
literature (Kittleson & Kienle 1998) with normal or no
significant mild increase LVESD and LVEDD. Neverthe-
less, it was not evaluated left ventricle volumes in this
research, this characteristic may reflect similarly, to what
occurs in obese, normotensive humans - eccentric hyper-
trophy of the left ventricle resulting from an increase in
preload associated with obesity. This eccentric hypertrophy
is a mechanism to normalize stress on the left ventricular
wall (Alpert 2001a, Vasan 2003). Similar data was not
encountered in the findings of other studies when inducing
obesity in dogs by administering hypercaloric diets, did
not observe any alterations in left ventricle wall thickness
(Verwaerd et al. 1996, Massabuau et al. 1997).
The significant mean regression of left ventricular
hypertrophy verified in group III after reaching target weight
corroborated the findings documented by other researches
that demonstrated the effect of weight loss on LVWS and
LVWD reduction in humans submitted to hypocaloric diets
(Sidó et al. 2000, Uwaifo et al. 2003).
The computerized electrocardiographic evaluation
initially showed an increase in mean P wave duration for
100%, 40% and 20% of the dogs in groups I, II and III, res-
pectively, compared with normal values for computerized
electrocardiography in literature (Wolf et al. 2000), this data
could indicate alteration in an electrical conduction thought
the atria in obese dogs, but further studies are necessary
to prove this hypothesis. After weight reduction, a decrease
in duration was observed in all groups, differing from that
reported in morbid obese humans (Alpert et al. 2001c).
Table 3. Mean values and standard deviation of the systolic (SAP), mean (MAP) and diastolic
(DAP) arterial blood pressure in mmHg from obese dogs Groups I, II and III (each group, n=6),
before and after weight loss
Group I Group II Group III
Before After Before After Before After
SAP 134±6Aa 118±25Aa 143±6ABa 137±7ABa 158±20Ba 144±11Bb
MAP 97±4 Aa 86±23 Aa 112±6 ABa 92±13 ABb 112±19Ba 102±9 Ba
DAP 82±13 Aa 68±24 Aa 90±8 Aa 73±17 Aa 90±18 Aa 77±6 Aa
A, B, C = means in the same line with different capital letters indicate statistical significance (p<0.05) among Groups I,
II and III.
a, b = means in the same line with different small letters indicate statistical significance (p<0.05) between before and
after times.
Table 4. Mean values and standard deviation of electrocardiographic parameters obtained from
obese dogs of Groups I, II and III (each group, n=6), before and after weight loss
Group I Group II Group III
Before After Before After Before After
Pms 45.40±3.91 Aa 42.20±2.17 Aa 46.80±4.09 Aa 42.40±1.34 Aa 50.80±4.27 Aa 47.40±2.88 Aa
PmV 0.27±0.06Aa 0.21±0.06Aa 0.25±0.12 Aa 0.26±0.08 Aa 0.7±0.06 Aa 0.27±0.05 Aa
QRSms 46.80±6.02 Aa 49.40±1.34 Aa 56.80±7.19 Aa 57.40±6.58 Aa 56.20±3.70 Aa 57.20±4.38 Aa
RmV 1.04±0.24 Aa 1.23±0.29 Aa 1.82±0.68 Ba 1.81±0.70 Ba 0.91±0.44 Ca 0.95±0.47 Ca
PRms 94.20±10.71 Aa 90.20±8.44 Aa 101.40±3.78 Aa 116.40±20.29Aa 98.60±10.69 Aa 104.80±8.67 Aa
QTms 183.4±10.60 Aa 198.00±12.61Aa 205.0±10.71Aa 203.40±13.67Aa 210.60±11.89Aa 201.40±16.86Aa
FCbpm 124.00±21.85Aa 102.80±19.03Aa 99.00±12.98 Aa 105.60±20.33Aa 105.80±17.48Aa 115.40±14.67Aa
Eixo 55.80±5.89 Aa 64.40±15.95 Aa 60.80±13.25 Aa 77.80±14.75 Aa 56.00±8.66 Aa 69.00±22.75 Aa
A, B, C = means in the same line with different capital letters indicate statistical significance (p<0.05) among Groups I,
II and III.
a, b = means in the same line with different small letters indicate statistical significance (p<0.05) between before and
after times.

Pesq. Vet. Bras. 30(2):167-171, fevereiro 2010
Effects of weight loss on the cardiac parameters of obese dogs 171
Arterial pressure values for all groups at both evaluation
times were found to be within the reference ranges for
canine species, they were not hypertension, like observed
by Rocchini et al. (2004) that conclude hypertension was
not directly related to obesity in dogs. As in this work, Brown
et al. (2007) observed that overweight dogs possessed
higher reference range arterial pressures in relation to
those of ideal body weight. As such, food restriction is
considered an important non-pharmacological treatment
for controlling arterial pressure, especially in dogs of
excessive weight (Rocchini et al. 1987, Rocchini et al.
1989).
This study demonstrated that, in consideration of the
weight loss protocol employed, dogs presented adequate
rates of body weight reduction. It also verified that weight
reduction reverts some of the cardiac structural alterations
observed through echocardiography, like eccentric hyper-
trophy in obese dogs above 30 kilograms. Systolic, mean
and diastolic arterial pressure dropped significantly in all
obese dogs after a 15% minimum loss of their initial body
weight.
Acknowledgments.- To Waltham Foundation (Project 2004/083) for
funding and to Royal Canin of Brazil for supporting this research.
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