52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Estimativa da proteína e gordura corporal em frangos de corte pelo método DXA
Camila Angelica Gonçalves1, Nilva Kazue Sakomura1, Edney Pereira da Silva1, Silvana Martinez Baraldi Artoni2,
Giuliana Milan de Andrade Rocha Garcia2, Rozana Wendler da Rocha3
Faculdade de Ciências Agrárias e Veterinárias, UNESP – Universidade Estadual Paulista, Campus de Jaboticabal, Departamento de Zootecnia.
Jaboticabal, SP, Brasil. e-mail: [email protected]
2
Faculdade de Ciências Agrárias e Veterinárias, UNESP – Universidade Estadual Paulista, Campus de Jaboticabal, Departamento de
Morfologia e Fisiologia Animal. Jaboticabal, SP, Brasil.
3
Faculdade de Ciências Agrárias e Veterinárias, UNESP – Universidade Estadual Paulista, Campus de Jaboticabal, Departamento de Clínica e
Cirurgia Veterinária. Jaboticabal, SP, Brasil.
1
Resumo: Este estudo avaliou o potencial da técnica absorciometria por duplo feixe de raios-X (DXA) para predizer
a composição corporal in vivo e do corpo depenado em frangos de corte. Trinta frangos de corte machos (Cobb 500)
foram criados sob condições padrão de temperatura e alimentação. Semanalmente cinco aves foram escaneadas e
em seguida sacrificadas para determinar a composição corporal por análise química. A análise da variância mostrou
diferenças significativas entre a composição determinada por DXA in vivo e post-mortem nas diferentes idades. Foi
realizada análise de regressão entre os valores determinados pelo DXA e análise química para estimar a composição
de proteína e extrato etéreo. A equação obtida para estimar a composição em proteína foi %CP= 53,64+0,74×Age–
0,06×BW+0,05×LM, R²=0,86; onde CP é proteína bruta, (%); Age é idade da ave, (dias); BW é peso corporal, (g);
LM é massa magra, (g). Para extrato etéreo a equação obtida foi %EE= 22,08+0,03×FM, R²=0,96; em que FM é
massa gorda, (g). Os resultados obtidos pela técnica DXA estão de acordo com os determinados quimicamente,
portanto, a técnica DXA pode ser uma alternativa para determinar a composição corporal in vivo de frangos de
corte, por meio das equações.
Palavras–chave: carcaça, gordura, idade, não-invasivo, predição, tecido magro
Estimation of protein and fat in broilers chickens by DXA method
Abstract: This study evaluated the potential of dual X-ray absorptiometry technique (DXA) to predict in vivo body
composition and whole carcass in broilers. Thirty male broilers (Cobb 500) were created under standard conditions
of temperature and feed. Weekly, five birds were scanned and then sacrificed to determine body composition by
chemical analysis. Analysis of variance showed significant differences between the compositions determined by
DXA in vivo and post-mortem at different ages. Regression analysis was performed between the values determined
by DXA and chemical analysis to estimate the protein and ether extract composition. The equation obtained for
estimating the composition of protein was %CP = 53.64+ 0.74×Age–0.06×BW+0.05×LM, R²=0.86, where CP is
crude protein (%); Age is bird age, (days); BW is body weight, (g); LM is lean mass, (g). The obtained equation for
ether extract was %EE =22.08+0.03×FM, R² = 0.96, where FM is fat mass, (g). The results obtained by the DXA
technique are in agree with those chemically determined, therefore, DXA method can be an alternative for
determining in vivo body composition in broiler chickens by means of the equations.
Keywords: age, bone, carcass, fat, lean tissue, noninvasive, prediction
Introduction
Body composition analysis is fundamental in animal research because regardless of the method used (in vivo
or in vitro), body composition provides useful information about genetic factors, growth pattern, age, gender,
nutritional status and change in the body composition in terms of lean meat yields (muscles) and fat, which are
factors that significantly affect the profitability of livestock production.
The DXA method has been used to measure body composition in broiler chickens (Mitchell, et al., 1997;
Swennen et al., 2004). DXA technology is based on the energy attenuation properties for x-rays that pass through
body tissues. Two different levels of energy are absorbed by various types of body tissue, differing body mass in
three classes: mineralized tissue (bone), fat mass (FM) and lean tissue (LM). However, this method still needs to be
validated by comparison with carcass chemical analysis (direct reference method) to use. Previous studies have
evaluated the DXA technique in chickens showed a high degree of accuracy when compared with the values
determined chemically.
This study aimed to evaluate the use of DXA to determine body composition in vivo in broilers.
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Página - 1 - de 3
52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Material e Methods
It was used 30 male broilers (Cobb-500) from 7-42 d-old raised in standard conditions. At 7, 14, 21, 28, 35
and 42 d, five birds were selected and identified for scanning on DXA equipment Hologic Dicovery (software
version 13.4.2) as both in vivo and post-mortem, using pediatric scanning module. The birds were fasted for two
hours before isoflurane administration (inhaled anesthetic) and positioned on the machine to scan (supine position,
with legs and wings flexed). After the scans, they received access to water and overnight fasted for 22 hours, and
then, were sacrificed by CO2 and plucked. Later DXA scans were performed immediately after slaughter (plucked
body) and after 24 hours of refrigeration (cold plucked body). A meat thermometer was used to measure the
temperature of the bodies. The results obtained by DEXA were: total weight (g), fat mass (g), lean mass (g) and
bone mineral content (g). For chemical analyzes the bodies were individually frozen (-20 °C), ground by a meat
grinder and homogenized. Representative body samples were lyophilized and analyzes performed in duplicate using
the Ankom XT-15 Fat Extractor (Ankom Technology), crude protein by Kjeldahl (Kjeltec 8400, Foss), water by
oven drying at 105 ° for 12 hours and the ash by subjecting the samples in a muffle furnace for 4 hours at 600 ° C.
The results were submitted to analysis of variance and t test was used to compare the averages for DXA scans in
vivo and post-mortem. Linear regression analysis was performed between body composition in vivo and chemical
analyzes using the SAS GLM procedures (Version 9.2) and 5% of significance level.
Results and Discussion
Analysis of variance showed significant differences due to in vivo, plucked body (33.6 °C) and cold plucked
body (5.9 °C) scans for fat mass (p-value = 0.0026), lean mass (p-value = 0.0032) and for the age of the birds in all
DXA parameters (p <0.0001) and there was also interaction between treatments and ages of the birds for fat mass
and lean mass. In the Table 1 it is possible to notice that after 42 days, the total mass and fat mass were higher than
other age groups. The bone mineral content (BMC) showed significant differences at 7 days of age, being lower
other to other ages and the lean mass was lower only at 42 days.
Table 1. Difference in the means determined by DXA in vivo,
plucked body and a cold plucked body throughout the
age of the birds.
Age (days) Total mass (g)
BMC (g)
Fat (%)
Lean mass (g)
7
150 B
1.01 B
10.55 B
88.45 A
14
370 B
1.17 A
10.14 B
88.69 A
21
660 B
1.21 A
10.35 B
88.44 A
28
1.11 B
1.19 A
9.85 B
88.94 A
35
1.93 B
1.22 A
9.89 B
88.89 A
42
2.70 A
1.30 A
12.23 A
88.46 B
p-value F
<0.001
<0.001
<0.001
<0.001
CV, %
8.85
12.46
8.98
1.16
Means followed by same letter in the column do not differ by SNK test.
These results suggest that changes are common due to the animal growth and tissue deposition and are not
due to the effect of scans at different temperatures of the bodies. The crude protein in the animal is constant,
however, at 42 days of age increases the fat deposition (Grey et al., 1983).
The regression between the results obtained by DXA and chemical analyzes are presented in Table 2.
Table 2. Estimates of linear equations to assess the chemical
body composition with DXA in vivo for %CP
(crude protein) and % EE (ether extract); a BW=
body weight, b LM = lean mass, c FM= fat mass
Models
R2
%CP= 53.64+0.74×age–0.06×BWa+0.05×LMb
0.86
c
0.96
%EE= 22.08+0.03×FM
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
The results show that future studies should take into account the changes in lean mass and fat mass in age,
that affect the proportion of water in the body.
Conclusions
This work is an important contribution to our understanding of how the DXA may be useful in determining
in vivo and post-mortem body composition in broilers. The results allow to help standardize the use of DXA as an
indirect method for body composition determination in broiler chickens.
However, few animals were used in this study and so we recommend larger-scale controlled trials to
investigate the differences in fat, lean and water distribution into the body, with an emphasis on changes on
individual body composition.
Acknowledgements
To the São Paulo Research Foundation (FAPESP) by financial support and CAPES Foundation
(Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the doctorate scholarship granted to the first
author.
References
Grey, T. C.; Robinson, D.; Jones, J. M.; Stock, S. W.; Thomas, N. L. 1983. Effect of age and sex on the
composition of muscle and skin from a commercial broiler strain. British Poultry Science 24:219–223.
Mitchell, A. D.; Rosebrough , R. W.; Conway, J. M. 1997. Body composition of chickens by dual energy X-ray
absorptiometry.Poultry Science 76:1746–1752.
Swennen,Q.; Janssens, G. P. J.; Geers, R.; Decuypere, E.; Buyse, J. 2004. Validation of Dual-Energy X-Ray
Absorptiometry for Determining In Vivo Body Composition of Chickens. Poultry Science 83:1348–1357.
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