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Semina: Ciências Agrárias, Londrina, v. 39, n. 2, p. 731-746, mar./abr. 2018
Received: Apr. 22, 2017 - Approved: Dec. 13, 2017
DOI: 10.5433/1679-0359.2018v39n2p731
Productive features of broiler chickens in hot weather: effects of
strain and sex
Características produtivas de frangos de corte: efeito da linhagem e
sexo
Dáphinne Cardoso Nagib do Nascimento1*; Leilane Rocha Barros Dourado2;
Jefferson Costa de Siqueira3; Stélio Bezerra Pinheiro de Lima2; Melina da
Conceição Macêdo da Silva1; Gabriela Gome da Silva1; Nilva Kazue Sakomura4;
Guilherme José Bolzani de Campos Ferreira2; Daniel Biagiotti2
Abstract
The objective of the present study was to evaluate the performance of broiler strains (Cobb 500, Ross
308, and Hubbard Flex) in hot weather. Environmental temperatures above thermal comfort trigger
responses of the animals to maintain homeothermia, which negatively affects productive performance.
A total of 2,160 chicks of both sexes, were distributed in an experimental design that was completely
randomized in a factorial arrangement of 3 × 2 (strains and sexes) with six replicates of 60 birds each.
Feed intake (FI), live weight (LW), weight gain (WG), and feed conversion (FC) were analyzed at
periods of 1–7, 1–21, 1–28, 1–42, and 1–49 days old. At 42 and 49 days old, the carcass weight (CW),
carcass yield (CY), breast yield (BY), thigh yield (TY), and drumstick yield (DY) were analyzed. The
strains differed in LW and WG in most periods, especially for Cobb broilers in the pre-start period (1–7
days) and Hubbard broilers in the last two periods (1–42 and 1–49 days). Except for the pre-initial stage,
which there was no inuence of the strains on FC, the Hubbard broilers showed the best FC, at 1–49
d, similarly to Cobb broilers. Regardless of strain, the males showed superior performance to that of
females. At 42 d, the Cobb broilers showed a superior BY to that of the other strains, presenting better
TY than did the Ross and Hubbard strains. At 49 d, the Cobb and Ross strains showed the best BY, with
the Hubbard strain having the greatest DY. Males showed higher values in cut yields, except in the BY
in which females showed better results.
Key words: Carcass yield. Genetics. Poultry industry.
Resumo
Objetivou-se avaliar o desempenho das linhagens de frangos de corte (Cobb 500, Ross 308 e Hubbard
Flex) criadas em clima quente. Temperatura ambientais acima do conforto térmico desencadeiam
respostas dos animais para a manutenção da homeotermia em detrimento do desempenho produtivo.
Foram utilizados 2160 aves, de ambos os sexos, distribuídas em delineamento experimental inteiramente
casualizado em esquema fatorial 3 x 2 (linhagem e sexo) com seis repetições de 60 aves cada. Foi
avaliado o consumo de ração (CR), ganho de peso (GP), conversão alimentar (CA) e peso vivo (PV),
1 Discentes, Universidade Federal do Piauí, UFPI, Teresina/Bom Jesus, PI, Brasil. E-mail: daphinnen@icloud.com; melinacms@
gmail.com; gabigomesbj@outlook.com
2 Profs., UFPI, Bom Jesus, PI, Brasil. E-mail: leilane@ufpi.edu.br; steliolima@ufpi.edu.br; guilherme.ferreira@ufpi.edu.br;
biagiotti@ufpi.edu.br
3 Prof., Universidade Federal do Maranhão, UFMA, Chapadinha, MA, Brasil. E-mail: jc.siqueira@ufma.br
4 Profª, Universidade Estadual Paulista, UNESP, Jaboticabal, SP, Brasil. E-mail: sakomura@fcav.unesp.br
* Author for correspondence
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nos períodos de 1 a 7, 1 a 21, 1 a 28, 1 a 42 e 1 a 49 dias. Aos 42 e 49 dias foram avaliados o peso de
carcaça (CAR), rendimento de carcaça (RC), rendimento de peito (RP), rendimento de coxa (RCX) e
rendimento de sobrecoxa (RSC). As linhagens diferiram em PV e GP na maioria dos períodos, com
destaque para as aves da linhagem Cobb no período pré-inicial (1 a 7 dias) e as aves Hubbard nos dois
últimos períodos. Com exceção à fase pré-inicial em que não houve inuência das linhagens sobre a
CA, as aves Hubbard apresentaram a melhor CA, sendo esta no período de 1 a 49 dias semelhante às
aves Cobb. Independente da linhagem, os machos apresentaram desempenho superior em relação às
fêmeas. Aos 42 dias as aves Cobb apresentaram RP superior às demais linhagens, sendo o melhor RCX
apresentado pelas aves Ross e Hubbard. Aos 49 dias as linhagens Cobb e Ross apresentaram o melhor
RP, sendo o maior RSC exibido pela linhagem Hubbard. Os machos tiveram valores superiores nos
rendimentos de corte, com exceção no RP em que as fêmeas demonstraram melhores resultados.
Palavras-chave: Avicultura. Linhagens. Rendimento de carcaça.
Introduction
For decades, those involved in the production
chain of broiler chickens have been concerned with
the potential for growth and body conformation of
poultry, since these characteristics are related to the
efciency and protability of the poultry sector.
Genetic enhancements have resulted in the current
broiler chicken strains, which are characterized by
faster weight gain and better feed conversion.
Broiler chicken have been successfully
commercialized, including live chickens and
industrialized products. In Brazil, among the
exported products, cuts represent 57.7% and whole
chickens 32.6%, followed by processed products
(ABEF, 2016). The diversity of chicken meat supply
has driven the present production to develop strains
that meet market needs.
Broiler farms comprise different strains, each
one presenting unique development and production
characteristics. However, for them to realize their
performance potential and carcass characteristics,
it is necessary to meet the requirements of these
animals, since growth and muscular development
are inuenced by factors such as nutrition,
environmental conditions, disease, and housing
density (HRUBY et al., 1994).
A limiting factor in the production of broiler
chickens in Brazil is the climate, characterized by
high ambient temperatures and relative humidity
in most regions, and it is necessary to modify the
environment to modulate the microclimate inside
aviaries, and thus minimize the negative effects
of heat stress and decrease the thermal amplitude,
which can be as detrimental to birds as heat
(DONALD, 1997).
The investment cost in facilities and equipment
of ambience is high and may be impractical for
some breeders, which consequently may not provide
the birds with a controlled thermal environment to
maximize their productive potential.
An alternative for producers would be to use
more heat resistant strains, and according to Deeb
and Cahaner (2001), this resistance can occur
naturally in the environment, through breeding
strains originating from hot regions or developed by
articial selection.
The performance and carcass characteristics
of modern broiler strains maintained within their
thermal comfort zones have been described, but
this information does not include bird development
under different climatic conditions. Where birds are
not kept in a suitably controlled environment, they
may perform poorly as expected, as they are not in
thermal comfort and need to be slaughtered over 42
days of age. Therefore, the objective of the present
study was to evaluate the performance and some
carcass characteristics of broiler chickens from
different strains and sexes, reared under heat stress
conditions.
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Productive features of broiler chickens in hot weather: effects of strain and sex
Materials and Methods
The experiment was carried out from March
11 to April 29, 2014 in the Poultry Sector of the
Technical College of Bom Jesus, Campus Professor
Cinobelina Elvas, Federal University of Piauí,
located in the municipality of Bom Jesus, PI (09°
04′ 26″ S, 44° 21′ 32″ W), with an average altitude
of 277 m. According to the climatic classication
of Köppen, the climate of the region falls into the
type Aw, considered a tropical zone with dry winters
(ALVARES et al., 2013).
For this study, we used 2,160 broilers, half of each
sex, from three breeding ocks: Ross 308, Cobb 500,
and Hubbard Flex at 42, 37, and 38 weeks of age,
respectively. The hatching eggs of the respective
strains were purchased from breeder farms located
in the states of Ceará, Minas Gerais, and Goiás, and
transported in suitable trucks to Teresina, PI, where
they were incubated. After reception, the eggs were
processed under similar conditions and incubated
in a Coopermaq brand hatchery. Sexing through
wing feather examination was performed in the
hatchery, and the birds were transported and housed
approximately 15 hours after hatching.
The birds were weighed and distributed in 36 2
m2 pens, at a stocking density of 30 birds/m2, in an
experimental shed 26 m long by 8 m wide, covered
with ceramic tiles, with a 3 m right foot, equipped
with movable yellow side curtains to aid in the
control of the ambience.
Each pen was tted with a bell water drinker,
cylinder feeder, and 50 watt incandescent bulb for
heating. Environmental temperatures and relative
humidity (maximum and minimum) were recorded
daily using a thermo-hygrometer located in the
geometric center of the shed, at the life zone height.
To evaluate the thermal comfort each week, the
thermal comfort index enthalpy (comfort index
enthalpy - CIE) was determined, based on the
following formula:
H = 6,7 + 0,243*Tbs + {UR / 100* 10^7,5 * Tbs
/ 237,3 + Tbs}
where: H is the enthalpy (kcal/kg of dry air), Tbs is
the dry bulb temperature (°C), and UR is the relative
humidity of the air (%). The result was multiplied by
4.18 for the unit of measurement (kJ). The enthalpy
values are divided into four bands represented by
four colors: comfort (green), alert (yellow), critical
(orange), and lethal (red) (BARBOSA FILHO et
al., 2007). As enthalpy tables were available for
data until the sixth week, in the present study, for
the evaluation of the thermal comfort in the seventh
week, data for enthalpy in the sixth week were used
as a reference.
The experimental design was completely
randomized in the following factorial arrangement:
3 × 2 (strains and sexes), 6 treatments, with six
replicates of 60 birds each, and the initial mean
weights (± s) of the Cobb, Ross and Hubbard strains
were: 40.4 ± 0.03; 41.4 ± 0.10, and 42.2 ± 0.12 g for
males, and 40.4 ± 0.05; 39.7 ± 0.13, and 41.3 ± 0.14
g for females, respectively.
Diets based on corn and soybean meal were
formulated to provide the nutritional requirements of
male broilers with superior performance according
to the recommendations of Rostagno et al. (2011)
(Table 1). The feeding program consisted of four
diets according to the age of the birds: 1–7, 8–21,
22–42, and 43–49 d. The animals had free access to
water and feed throughout the experimental period.
The light program during the experimental
period consisted of 23 h (natural + articial light)
until d 7, 20 h (natural + articial light) from d 8 to
42, then increased to 22 h (natural + articial light)
thereafter.
At d 7, 21, 28, 42, and 49, all birds and left over
rations from each experimental unit were weighed
to evaluate the performance characteristics. The
variables analyzed were weight gain (WG), feed
intake (FI), feed conversion (FC), and live weight
(LW). Mortality was recorded daily, and the
subsequent calculation of the average feed intake and
feed conversion was determined (SAKOMURA;
ROSTAGNO, 2016).
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At d 42 and 49, three birds with body weights
close to the average of the pen (± 10%) were fasted
for 6 h and slaughtered to determine eviscerated
carcass weight (CW), carcass yield (CY), breast
yield (BY), thigh yield (TY), and drumstick yield
(DY). CY was calculated based on the relationship
between CW (without feathers, viscera, feet, head,
and neck) and LW. The parts yield was calculated
based on the ratio between the cut weight and CW.
Table 1. Ingredients and nutrient composition of the feeds used in the trial.
Ingredient (%) 1–7 8–21 22–42 43–49
Corn 48.738 54.589 58.803 63.427
Soybean meal 43.826 37.994 33.214 28.929
Soybean oil 3.439 3.718 4.772 4.956
Dicalcium phosphate 1.880 1.518 1.198 0.990
Limestone 0.779 0.814 0.732 0.653
Salt 0.452 0.482 0.452 0.432
Mineral and Vitamin Premix1,2,3,4 0.400 0.400 0.400 0.200
DL-Methionine (99%) 0.306 0.29 0.256 0.225
L-Lysine HCL (78,5) 0.136 0.158 0.152 0.169
L-Threonine (99%) 0.044 0.037 0.021 0.019
Total 100.00 100.00 100.00 100.00
Nutritional composition
ME (kcal/kg) 2.960 3.050 3.175 3.250
Crude protein (%) 24.00 22.00 20.25 18.64
Calcium (%) 0.920 0.841 0.711 0.614
Available phosphorus (%) 0.470 0.401 0.332 0.286
Sodium (%) 0.220 0.210 0.198 0.190
Digestible lysine (%) 1.324 1.217 1.096 1.006
Digestible methionine (%) 0.615 0.579 0.525 0.477
Digestible methionine + cistyne (%) 0.953 0.876 0.800 0.734
Digestible threonine (%) 0.861 0.791 0.712 0.654
Digestible tryptophan (%) 0.283 0.249 0.223 0.201
Digestible valine (%) 1.024 0.936 0.855 0.785
Crude ber (%) 3.437 2.958 2.778 2.631
Provided per kg of product 1(pre-starter): folic acid – 200 mg; biotin-10 mg; chloro hydroxyquinoline -7,500 mg: zn – 17.50 g; vit.
A – 1,680,000 UI; vit. B1 – 436.50 mg; vit. B12- 2,400 mg; vit. B2 – 1,200 mg; vit. B6 - 624 mg; vit. D3 – 400,000 UI; vit. E –
3,500 UI; vit. K 3 – 360 mg; niacin – 8,399 mg; nicarbazin - 25 g: pantothenic acid – 3,120 mg; choline – 78.10 g; Se - 75 mg; Fe
11.25 g; mn – 18.74 g; Cu -1,997 mg; I – 187 mg. 2(starter): folic acid – 199 mg; biotin - 10 mg; chloro hydroxyquinoline – 7,500
mg; Zn – 17.50 g; vit. A – 1,680,000 UI; vit. B1 – 436.50 mg; vit. B12 – 2,400 mg; vit. B2 – 1,200 mg; vit. B6 – 624 mg; vit. D3 –
400,000 UI; vit. E – 3500 UI; vit. K 3 – 360 mg; niacin – 8400 mg; monensina -25 g; pantothenic acid – 3119 mg; choline – 80.71
g; Se – 75 mg; Fe 11.25 g; Mn – 18.74 g; Cu – 1996 mg; I – 187.47 mg. 3(grower): folic acid – 162.50 mg; chloro hydroxyquinoline
– 7,500 mg: Zn – 17.50 g; vit. A – 1,400,062.50 UI; vit. B1 – 388 mg; vit. B12 - 2,000 mg; vit. B2 – 1,000 mg; vit. B6 - 520 mg;
vit. D3 – 360,012 UI; vit. E - 2500 UI; vit. K 3 – 300 mg; niacin – 7000 mg; salinomycin – 16.50 g: pantothenic acid – 2600 mg;
choline – 71.59 g; Se – 75 mg; Fe 11.25 g; Mn – 18.74 g; Cu – 1996 mg; I – 187.47 mg. 4(nisher): folic acid – 162.50 mg; zinc
oxide – 17.500 mg; Se – 75 mg; vit. A – 140,000 UI; vit. B1 – 388 mg; vit. B12 – 2,000 mg; vit. B2 – 1,000 mg; vit. B6 - 520 mg;
vit. D3 – 1,600 UI; vit. E - 2500 mg; vit. K 3 – 300 mg; Zn - 70 ppm; niacin – 7,000 mg; pantothenic acid – 2,600 mg; choline –
71,593.49 mg; Fe 11.250 mg; Mn – 18.750 mg; Cu - 2000 mg; I – 187.50 mg, antioxidant additive – 25,000 mg; halquinol 7,500
mg; salinomycin – 16,500 mg.
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Productive features of broiler chickens in hot weather: effects of strain and sex
The performance data and carcass characteristics
of the birds, referring to the different evaluation
periods were initially submitted to normality
tests (Cramer-Von Mises) and homoscedasticity
(Levene); and once these assumptions were
met, they were submitted to analysis of variance
according to the statistical model:
Yij(k) = μ + Straini + Sexj + Strain × Sexij + ϵij(k)
where Yij(k)= FI, WG, FC, LW, CW, CY, BY, TY,
and DY of birds of the i-th lineage in the jth sex; μ
= overall mean effect; Straini = i-th lineage effect;
Sexj = jth sex effect; Strain × Sexij = interaction
effect between ith Strain and jth Sex, and eij(k) =
experimental error. Subsequently, the means of the
analyzed variables were analyzed by the SNK test
(P ≤ 0.05), using SAS 9.0 Software (SAS Institute,
2002), through the “GLM” procedure.
Results and Discussion
The mean, minimum, and maximum
temperatures and average relative humidity inside
the room during the experimental period were 28.1
± 0.7; 22.0 ± 1.2; 34.2 ± 0.9; and 73.6 ± 13.7%,
respectively.
The mean and maximum temperatures recorded
from the second week of life were above the
recommended comfort temperatures in the strains
manuals, which indicate temperatures below 26
°C from 18 d of age (COBB, 2005; HUBBARD,
2007; ROSS, 2012). Minimum periods on most
experimental days were observed at about 5:00
and the duration of the mild temperature over a
24 h period was short. The thermal comfort index
enthalpy indicated that the birds were only in thermal
comfort in the second week of life (green band),
being in the lower and upper alert range (yellow)
in the rst and third week, respectively. After the
third week, the birds were in a critical environment
(orange band), which possibly inuenced their
performance (Table 2).
Table 2. Minimum, maximum, and mean environmental temperature (°C) and relative humidity (%), standard
deviation, and enthalpy comfort index (ECI) weekly, during the period from March 11 to April 29, 2014.
Period
(days)
Temperature (°C) Relative humidity (%) IEC (KJ/Kg dry air)
Minimum Maximum Mean Minimum Maximum Mean
1 to 7 23.3 34.2 28.75 ± 0.1 63.0 82.1 72.5 ± 0.3 76.81
76.14
75.48
76.40
76.86
73.66
72.88
8 to 14 22.9 34.0 28.45 ± 0.1 63.0 81.9 72.4 ± 0.4
15 to 21 21.1 34.9 28.00 ± 0.1 63.1 84.1 73.6 ± 0.2
22 to 28 22.4 34.1 28.25 ± 0.3 65.3 84.8 75.0 ± 2.1
29 to 35 22.1 34.0 28.05 ± 0.3 69.4 87.6 78.5 ± 0.8
36 to 42 20.5 34.4 27.45 ± 0.1 57.1 84.8 70.9 ± 2.4
43 to 49 21.5 33.4 27.45 ± 0.3 48.6 87.1 67.8 ± 3.2
No interactions (P > 0.05) between strains and sex
were observed for any of the performance variables
evaluated in the pre-initial period (1–7 d) (Table 3),
indicating that these factors act independently. It
was observed that the strains inuenced (P < 0.05)
the FI, WG, and LW, whereas the sex inuenced
(P < 0.05) the WG and LW of the birds, without
inuence (P > 0.05) of strains or sex on the FC in
the pre-initial period.
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Ross FI was similar to that of the Cobb and
Hubbard strains, Cobb consumption being 6.1%
higher than that of Hubbard. Stringuini et al. (2003),
when comparing the performance of four broiler
strains, did not observe differences in FI between
Cobb and Ross strains in the rst week of life,
corroborating the results of the present study.
The Cobb strain presented a superior WG to that
of the Hubbard (8.9%) and Ross (3.8%) strains,
being 4.9% superior to that of Hubbard. The effect
of strains on the WG of birds at 1– 7 d was found
by Abdullah et al. (2010), who veried that the
Hubbard Classic strain presented superior WG in
relation to Ross and Hubbard JV strains. Similarly
to WG, the Cobb strain had a higher LW than the
Hubbard (5.3%) and Ross (3.3%) strains, which
was 2.1% higher than Hubbard.
Table 3. Mean of feed consumption (FI), weight gain (WG), live weight (LW), and feed conversion (FC) of different
strains of males and females at 1–7 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
FI (kg) Male 0.123 0.121 0.111 0.118 5.40 0.035 0.313 0.068
Female 0.118 0.114 0.116 0.116
Mean 0.121a 0.117ab 0.114b
WG (Kg) Male 0.113 0.108 0.101 0.107A 3.36 < 0.001 0.006 0.109
Female 0.107 0.104 0.101 0.104B
Mean 0.110a 0.106b 0.101c
Male 0.154 0.149 0.143 0.149A 2.55 < 0.001 < 0.001 0.175
LW (kg) Female 0.147 0.143 0.142 0.144B
Mean 0.151a 0.146b 0.143c
FC Male 1.089 1.121 1.099 1.103 5.77 0.629 0.455 0.411
Female 1.107 1.102 1.148 1.119
Mean 1.098 1.111 1.123
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
No effects of strain (P > 0.05) on FC were
observed, despite differences found between FI and
strains, showing that in the pre-initial period, Cobb,
Ross, and Hubbard birds gained weight with similar
efciencies. Considering the sex, it was observed
that males presented higher WG (2.9%) and LW
(3.4%) than that of females, independent of the
strain, corroborating with the results of Stringuini
et al. (2003) who observed that WG and LW of
male broilers of the Ross, Cobb, Avian Farms, and
Arbor Acres strains at 1–7 d were 3.6% and 2.8%,
respectively, higher than that of females.
According to Yassin et al. (2009) the main
morphophysiological changes of the digestive,
immunological, and thermoregulatory systems
occur in the rst seven days of life of the birds,
which supports the importance of this period for
their development. In addition to these factors,
the rapid growth of broilers reduces the time of
poultry in the eld, thus increasing the importance
of satisfactory performance in the rst week after
hatching. However, each strain has a growth
potential over a specic period (GOLIOMYTIS et
al., 2003; SANTOS et al., 2005); thus, a greater live
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Productive features of broiler chickens in hot weather: effects of strain and sex
weight or weight gain from one strain to another in
the pre-initial period may not translate into greater
growth over the life of the bird.
No interactions (P > 0.05) between strain and sex
were observed for any of the performance variables
evaluated in the period of 1–21 d (Table 4), in which
FI and FC were inuenced by the strain (P < 0.05).
The performance variables were inuenced by sex
(P < 0.05), with the exception of FC (P > 0.05).
The birds of the Ross strain had FI that was
higher by 1.4% and 3.4% than that of the birds of
the Cobb and Hubbard strains, respectively, and the
FI of the Hubbard birds was 2.0% lower than that
of the Cobb birds. Abdullah et al. (2010) in a study
with four strains at 14–21 d, found differences in
FI, where the FI of the Ross birds was 12.3% higher
than that of the Hubbard JV birds. The absence of
effect of the strains on WG and LW agrees with the
results of Farran et al. (2000) when evaluating the
performance of three broiler strains (Arbor Acres,
Lohman, and Ross) at 1–21 d, nding no strain
effect on LW.
The Hubbard birds presented a lower FC than
those of the Cobb and Ross strains, which showed
similarities. Although there were no differences in
WG between the strains at 1–21 d, the lower FI of
Hubbard than Cobb and Ross strains, resulted in
improved FC, indicating greater growth of Hubbard
birds between d 7 and 21, since the birds of the
Hubbard strain presented inferior WG and LW in
the pre-initial period (1–7 d).
Table 4. Mean of feed consumption (FI), weight gain (WG), live weight (LW), and feed conversion (FC) of different strains of
males and females at 1–21 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
FI (kg) Male 0.982 0.992 0.961 0.978A 1.32 < 0.001 < 0.001 0.795
Female 0.930 0.946 0.914 0.930B
Mean 0.956b 0.969a 0.937c
WG (Kg) Male 0.677 0.673 0.693 0.681A 2.92 0.238 < 0.001 0.483
Female 0.637 0.647 0.648 0.644B
Mean 0.657 0.660 0.670
Male 0.718 0.715 0.735 0.722A 2.76 0.172 < 0.001 0.517
LW(kg) Female 0.677 0.687 0.689 0.684B
Mean 0.697 0.701 0.712
FC Male 1.451 1.474 1.388 1.438 2.49 < 0.001 0.578 0.533
Female 1.462 1.462 1.411 1.445
Mean 1.456a 1.468a 1.399b
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
Analyzing the sex, the males showed a higher
FI by 5.2%; WG by 5.7%, and LW by 5.6% than
females; corroborating with the results of Moreira
et al. (2004), who also observed a higher FI (8.9%)
and WG (9.8%) of the males based on both sexes of
three broiler strains (Ross, Cobb, and Hybro).
No interactions (P > 0.05) between strain and sex
were observed for any of the performance variables
for 1–28 d (Table 5). Similarly to the previous
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period (1–21 days), Ross birds presented the highest
FI, which was 3.1% and 1.9% higher than that of
the Cobb and Hubbard birds, respectively, and there
were no differences between Cobb and Hubbard
birds. The superiority of the Ross strain did extend to
WG and LW, as these were similar to those observed
in the Cobb and Hubbard strains. However, despite
the similarity in FI of the Cobb and Hubbard birds,
the latter presented WG (4.6%) and LW (4.5%)
higher than the Cobb birds, suggesting a higher WG
efciency of Hubbard birds. It was observed that the
birds of the Hubbard strain presented the best FC,
3.3% higher than Cobb, and 4.3% higher than Ross
birds, with no differences between these strains.
The CR, GP, and PV values of the birds at 1–28
d were lower than the reference values presented
in the guidelines of the lines, with Cobb, Ross, and
Hubbard strains having higher PVs by 35%, 27%,
20%, respectively, than birds of the respective
lineages in the present study (HUBBARD, 2007;
COBB, 2005; ROSS, 2012), and this inferiority
may be attributed to the high environmental
temperatures during the experimental period, with
averages above the comfort range for birds from the
second week of life.
Several authors have reported reduced
consumption and decreased performance of broiler
chickens exposed to heat stress (OLIVEIRA et al.,
2006).
The analysis of the performance of the three
strains during 1–7, 1–21, and 1–28 d suggested that
birds of the Cobb strain showed higher sensitivity
to high environmental temperatures than Ross and
Hubbard birds, since 1–7 d Cobb birds showed
higher WG and LW, and in subsequent periods, the
superiority of these variables was not maintained.
Table 5. Mean of feed consumption (FI), weight gain (WG), live weight (LW), and feed conversion (FC) of different
strains of males and females at 1–28 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
FI (kg) Male 1.643 1.695 1.669 1.669A 2.26 0.008 < 0.001 0.875
Female 1.537 1.584 1.548 1.556B
Mean 1.590b 1.639a 1.608b
WG (Kg) Male 1.086 1.114 1.143 1.114A 3.17 0.006 < 0.001 0.797
Female 1.002 1.017 1.040 1.020B
Mean 1.044b 1.066ab 1.092a
LW(kg)
Male 1.127 1.156 1.186 1.156A 3.06 0.005 < 0.001 0.765
Female 1.042 1.057 1.082 1.060B
Mean 1.084b 1.106ab 1.133a
FC Male 1.513 1.522 1.460 1.498B 1.95 < 0.001 0.006 0.835
Female 1.535 1.558 1.488 1.527A
Mean 1.524a 1.540a 1.474b
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
In relation to sex, the same tendency of the
previous period was also observed, with males
presenting higher FI (6.8%), WG (8.5%), and LW
(8.3%) values than that of females, presenting an
improvement of 1.9% in FC. Males presented a
higher growth rate and body protein deposition
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Productive features of broiler chickens in hot weather: effects of strain and sex
(MARCATO et al., 2008), indicating a higher feed
intake and lower feed conversion than females.
The comparison of the performance
characteristics between the sexes from d 21 is an
important tool for the poultry industry. Some markets,
such as the Middle East, require a differentiated
product obtained by slaughtering poultry aged 25
to 33 d with an average slaughter weight of 1.450
kg (SANDI, 2011). In this type of production
where the birds are slaughtered younger, females
are commonly used, since the abundant production
of females of advanced ages is not feasible owing
to a greater deposition of body fat in relation to
males, and consequently a higher feed conversion.
However, the use of male chickens for this type of
production can be indicated for hot regions and for
sheds with limited technology in ambience control,
because with increased age the birds become more
sensitive to high ambient temperatures, with a
possible decrease in performance and increase
in mortality risk, highlighting the importance of
studies that assess the effects of strains and sex
under hot weather conditions.
During 1–42 d, no interactions (P > 0.05)
between strain and sex were observed for any of the
performance variables, with strain and sex effects
(P < 0.05) for the performance variables evaluated,
except for FI that did not have a strain effect (P >
0.05) (Table 6).
The Hubbard birds showed a higher WG of 8.2%
in relation to the Cobb birds and 5.0% in relation
to the Ross birds, with no differences between the
Cobb and Ross strains. However, Moreira et al.
(2004) working with the Cobb, Ross, and Hybro
strains observed that the Ross birds presented a
3.1% higher WG than the Cobb birds.
Table 6. Mean of feed consumption (FI), weight gain (WG), live weight (LW), and feed conversion (FC) of different
strains of males and females at 1– 42 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
FI (kg) Male 3.364 3.441 3.382 3.396A 4.20 0.384 0.008 0.309
Female 3.208 3.234 3.349 3.256B
Mean 3.286 3.337 3.365
WG (Kg) Male 1.904 2.012 2.081 1.999A 4.30 0.004 < 0.001 0.310
Female 1.794 1.798 1.918 1.836B
Mean 1.849b 1.905b 2.000a
LW (kg)
Male 1.944 2.054 2.124 2.041A 4.21 0.004 < 0.001 0.302
Female 1.835 1.838 1.960 1.877B
Mean 1.890b 1.945b 2.041a
FC Male 1.769 1.711 1.626 1.702B 4.09 0.009 0.003 0.217
Female 1.788 1.803 1.746 1.779A
Mean 1.779a 1.757a 1.686b
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
Following the trend of WG, the Hubbard birds
presented a higher LW than the Cobb (8.0%) and
Ross (4.9%) birds. Mehaffey et al. (2006) in a
comparative study with ve broiler strains at 42
d of age observed similarities between the LW of
four genetic groups, with the highest LW strain
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Nascimento, do D. C. N. et al.
being 5.8% higher than the average LW of the other
strains. The best FC observed during 1–42 d of age
was obtained in the birds of the Hubbard line, being
5.2% and 4.0% superior to the birds of the Cobb
and Ross strains, respectively, and no differences
were observed between them. The males presented
the highest FI (4.3%), WG (8.9%), and LW (8.4%),
and better FC (4.3%) than that of females. Moreira
et al. (2004) in a study with Cobb, Ross, and Hybro
strains from 1 to 42 d of age, also observed higher
FI (12.4%) and WG (17.4%) in males than that in
females, accompanied by an improved FI (4.3%). In
another study, Brewer et al. (2012), comparing the
effects of four strains and sex on broiler chickens,
observed that the LW of males, regardless of strains,
was 13.6% higher than that of females.
During 1–49 d, no interactions (P > 0.05)
between strain and sex were observed for any of the
performance variables (P < 0.05) (Table 7). Cobb
FI was 5.2% and 3.9% lower than that in birds of
the Hubbard and Ross strains, respectively, and
there were no differences between them. Similarly,
Flemming et al. (1999) studied different broiler
strains (Cobb, Hubbard, Ross, Arbor, and Isa) from
1 to 47 d of age and observed that Cobb birds also
had a lower intake than Hubbard (2.1%) and Ross
(0.2%) birds, nding no differences between the
two latter strains.
The Hubbard birds presented higher WG by 9.3%
and 6.6% than Cobb and Ross birds, respectively,
and there were no differences between these two
latter strains. The Hubbard birds presented the
highest LW, 9,2% and 6,5% superior to that of Cobb
and Ross strains, respectively. As observed in the
previous periods, the LW of the birds at 49 d was
lower than that recommended by the companies
supplying the strains, which according to Cobb,
Ross, and Hubbard manuals suggested live weights
at 49 days of 3,786 3,695, and 3,076 kg (HUBBARD,
2007; COBB, 2005; ROSS, 2012), respectively.
These differences were probably owing to the
sensitivity to high environmental temperatures, as a
consequence of the reduction in the FI and decrease
in the WG of the birds.
Table 7. Mean of feed consumption (FI), weight gain (WG), live weight (LW), and feed conversion (FC) of different
strains of males and females at 1–49 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
FI (kg) Male 4.143 4.348 4.339 4.276A 3.43 0.002 0.001 0.522
Female 3.982 4.108 4.234 4.108B
Mean 4.062b 4.228a 4.286a
WG (Kg) Male 2.365 2.467 2.617 2.483A 4.35 < 0.001 < 0.001 0.507
Female 2.218 2.231 2.391 2.280B
Mean 2.291b 2.349b 2.504a
LW (kg)
Male 2.405 2.508 2.660 2.524A 4.27 < 0.001 < 0.001 0.518
Female 2.258 2.271 2.432 2.320B
Mean 2.331b 2.389b 2.546a
FC Male 1.756 1.764 1.660 1.726B 4.18 0.020 0.004 0.504
Female 1.796 1.843 1.771 1.804A
Mean 1.776ab 1.803a 1.715b
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
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Productive features of broiler chickens in hot weather: effects of strain and sex
In regions such as Southeast Piauiense,
characterized by high environmental temperatures,
producers who do not have air-conditioned sheds
need to prolong the duration of the birds in the
shed so that they reach the appropriate weight of
slaughter; when choosing a certain strain, it is
therefore necessary to know the FI and FC specic
for each genotype, and not only the WG and LW of
the birds.
Despite the similarity in FI between Hubbard
and Ross birds, the FC of the Hubbard birds was
4.9% higher than that of Ross birds, owing to the
WG superiority presented by the Hubbard birds.
Cobb birds presented a lower FI (5.2%) and WG
(8.5%) in relation to the Hubbard birds; however,
the FC of the birds of these strains was similar, as
well as between the Cobb and Ross strains.
The males presented higher FC (4.9%), WG
(8.9%), and LW (8.8%), and better FC (4.4%) than
that of females, independent of strain. Shin et al.
(2012), in a study with different broiler strains of
both sexes, also observed superiority in male LW
(20.6%) and a better FC (4.3%) than that of females,
suggesting males would be more suitable for
advanced slaughter age, when the goal is to market
live birds.
It was observed that none of the carcass traits
evaluated at 42 d presented a relationship (P > 0.05)
between strain and sex. However, independent
effects (P < 0.05) of strain and sex on CW, BY, and
TY were observed, with no effect (P > 0.05) of these
factors on CY and DY (Table 8).
At 42 d of age, Hubbard birds presented similar
CY to Ross birds, being 12.1% higher than the Cobb
strain, and there were no differences between Ross
and Cobb birds. However, Abdullah et al. (2010)
evaluated the carcass characteristics of the Hubbard,
Ross, and Lohman strains at 43 d, and found that the
Hubbard line presented a CY 10.0% higher than that
of the Ross strain.
The Cobb birds presented a BY that was higher
by 1.14% and 1.69% in relation to the Ross and
Hubbard birds, respectively. The Ross line presented
a 1.55% higher by than that of the Hubbard strain,
with the lowest BY. Scheuermann et al. (2003)
evaluated breast muscle growth in different
commercial broiler strains, and observed that birds
with higher BY had a longer period of muscle
deposition, thus increasing the weight and yield of
this muscle. The breast is considered an important
cut that corresponds to the highest proportion of
the broiler carcass, so that small differences in the
yields of this cut can be economically important.
Therefore, some poultry companies emphasize
breast weight and yield in their breeding programs,
to provide lineages that specically address the
industrial segments that prioritize BY, emphasizing
the importance of evaluating this characteristic in
studies with broiler chickens.
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Nascimento, do D. C. N. et al.
Table 8. Mean of carcass weight (CW), carcass yield (CY), breast yield (BY), thighs yield (TY), and drumstick yield
(DW) of different strains of males and females at 42 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
CW (kg) Male 1.73 1.90 1.95 1.86A 9.37 0.019 < 0.001 0.764
Female 1.55 1.62 1.72 1.63B
Mean 1.64b 1.76ab 1.84a
CY
(%)
Male 72.67 72.08 72.47 72.407 2.30 0.386 0.781 0.240
Female 71.51 72.62 73.56 72.56
Mean 72.09 72.35 73.01
BY
(%)
Male 34.45 32.79 31.37 32.87B 3.68 < 0.001 0.007 0.552
Female 35.02 34.45 32.77 34.08A
Mean 34.76a 33.62b 32.07c
TY
(%)
Male 13.20 14.09 14.61 13.97A 3.99 < 0.001 < 0.001 0.062
Female 12.47 13.13 12.84 12.81B
Mean 12.83b 13.61a 13.73a
DY
(%)
Male 13.78 14.49 14.34 14.203 7.88 0.481 0.165 0.467
Female 13.79 14.02 13.23 13.68
Mean 13.78 14.26 13.78
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
Considering TY, it was observed that the
Hubbard and Ross birds were superior by 0.9 and
0.8%, respectively, to that of Cobb birds, presenting
similar TYs to each other. Marcato et al. (2008),
when comparing thigh growth between Cobb and
Ross strains up to 56 d of age, observed that Ross
birds presented higher thigh growth rates after 35 d
of age, with a higher weight of this cut at advanced
ages.
Males presented higher CY (14.1%) and TY
(1.16%), but lower BY (1.21%) values than those
of females, concurring with the study of López et
al. (2011), in which the females had a BY 0.75%
higher than that of males. At 49 d of age there was
no interaction (P > 0.05) between strains and sex for
the carcass traits evaluated, except for (P < 0.05) TY.
As at 42 d, the Hubbard strain presented a similar
CY to the Ross birds, being 11.6% superior that of
Cobb strain birds, and there were no differences
between the Ross and Cobb strains at 49 d. No
differences were observed in BY between the birds
of the Cobb and Ross strains, which were superior to
the Hubbard strain by 1.7% and 1.6%, respectively.
Both strain and sex were found to affect TY; males
of Hubbard birds presented the highest TY, which
were 1.57% and 1.83% higher than that in Cobb
and Ross strain males, which did not differ from
each other. Among the females, no differences were
observed in TY among the lines of the present study.
(Table 9).
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Productive features of broiler chickens in hot weather: effects of strain and sex
Table 9. Mean of carcass weight (CW), carcass yield (CY), breast yield (BY), thighs yield (TY), and drumstick yield
(DW) of different strains of males and females at 49 d of age.
Variable Sex
(S)
Strain (St) Probability
Cobb Ross Hubbard Mean CV (%) St S StxS
CW (kg) Male 1.81 1.96 1.99 1.92A 9.01 0.017 < 0.001 0.331
Female 1.63 1.62 1.85 1.70B
Mean 1.72b 1.79ab 1.92a
CY
(%)
Male 75.31 75.00 76.89 75.73 4.56 0.635 0.681 0.523
Female 76.46 74.44 74.84 75.26
Mean 75.90 74.72 75.86
BY
(%)
Male 33.04 33.43 31.22 32.56B 4.14 0.008 0.003 0.487
Female 34.81 34.15 33.22 34.06A
Mean 33.92a 33.79a 32.22b
TY
(%)
Male 13.18Ab 12.92Ab 14.75Aa 13.62 4.86 < 0.001 < 0.001 0.046
Female 12.13Ba 12.41Aa 12.90Ba 12.48
Mean 12.65 12.67 13.83
DY
(%)
Male 14.29 13.95 14.89 14.38A 5.86 0.050 0.002 0.961
Female 13.39 13.09 13.85 13.44B
Mean 13.84ab 13.52b 14.37a
Mean followed by a common letter, lowercase in the row and uppercase in the column, do not differ statistically according to the
SNK test (P > 0.05).
In contrast to the previous age, in which the
strains did not inuence DY, at 49 d the DY of
Hubbard strain birds was similar to that of the Cobb
birds and was 0.85% higher than that of the Ross
birds, with no differences between Ross and Cobb
strains. At 49 d, males had higher CY (11.5%), TY
(1.14%), and DY (0.94%) values than females;
however, BY was lower by 1.5% in females.
In general, the results showed that the Cobb, Ross,
and Hubbard strains presented different carcass
and performance characteristics, which increase
the complexity in choosing between the different
genetic groups. Therefore, knowing the way the
birds are sold, together with the environmental
conditions in which they will be kept, is essential
when choosing the strain and the sex.
The birds of the Hubbard strain under conditions
of high ambient temperatures showed enhanced
performance characteristics, especially in the
later periods, than the other strains. Therefore,
they could be attractive for commercial producers
of live chickens, although they are not yet in the
northeastern market for this purpose owing to the
white color of their legs. The performance of the
Hubbard strain in advanced ages reinforces the
discussion that birds with superior performance in
the pre-initial phase (1–7 d) do not necessarily reach
greater slaughter weight (42 or 49 d), as shown in
this study. However, the greater weight at slaughter
may not be attractive for markets that prioritize
cuts, since higher performances do not necessarily
translate to higher yields of cut, since Ross and
Cobb birds, despite inferior performance, presented
higher BY in relation to Hubbard birds, emphasizing
the importance of the type of commercialization or
production when choosing a certain strain or sex.
It is important to emphasize that the climatic
conditions in which the birds were reared in
the present study were different from those
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Nascimento, do D. C. N. et al.
recommended by the strain manuals and thus we
observed that the performance of the birds also
differed from the reference values found in the
manuals.
Conclusion
Broiler chickens of the different strains studied
presented performance data lower than the
reference values in their respective manuals when
submitted to thermal stress during the growth and
nishing period. The Hubbard Flex strain was
showed enhanced performance variables than the
other strains, and the Ross 308 and Cobb 500 strains
showed enhanced cut yields. The males showed
better performance and carcass characteristics than
females, except for BY.
Acknowledgments
We would like to thank ASA Alimentos,
CIALNE, and Granja Planalto LTDA for the
donation of the hatching eggs, and COAVE for the
incubation process.
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