A. SALAHI, M. MOOSANEZHAD KHABISI, A. PAKDEL, A. BAGHBANZADEH
Turk. J. Vet. Anim. Sci.
2012; 36(2): 159-167
© TÜBİTAK
doi:10.3906/vet-1101-750
Research Article
Effects of cold stress during transportation on hatchability and
chick quality of broiler breeder eggs
1,
2
3
Ahmad SALAHI *, Mozhdeh MOOSANEZHAD KHABISI , Abbas PAKDEL , Ali BAGHBANZADEH
4
1
Department of Animal Science, Varamin–pishva Branch, Islamic Azad University, Varamin, Tehran - IRAN
2
Department of Animal Science, Kahnooj Branch, Islamic Azad University, Kahnooj, Kerman - IRAN
3
Department of Animal Science, Faculty of Agricultural Sciences and Engineering, University of Tehran, Karaj - IRAN
4
Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran,
Tehran - IRAN
Received: 26.01.2011
Abstract: In this experiment 72,000 broiler breeder eggs (Ross 308 strain) collected from 36-week-old flocks were
subjected to cold stress during transportation. Eggs were allocated to 4 temperature groups (treatments): 1.2 °C, 1-2 °C,
2.5-3.9 °C, 4-6 °C, and a control group, 21-22 °C. Each treatment had 14,400 eggs, and data were analyzed in a completely
randomized design. The results of this study showed that cold stress had a significant effect on percentage of egg weight
loss (P < 0.001), and minimal egg weight loss occurred in the control group. The percentage of exploders and early
hatched chicks and chick weight were higher in the below zero temperature treatment than the other groups (P < 0.01).
Cold stress had a significant effect on chick length, hatchability, and the hatching of fertile eggs (P < 0.001). The effects
of cold stress on chick yield and body weight uniformity were significant (P < 0.01). The effect of cold stress on hatchery
byproduct efficiency was significant (P < 0.001), but did not affect fertility. Cold stress also had significant effects on
early (1-8 days), middle (9-17 days), and late mortality (20-21 days); total embryo mortality; and exposed brain. Ectopic
viscera was significant (P < 0.001), and most mortality was observed in below 4 °C treatments. Total percentages of
malpositions and deformity (P < 0.001) and egg contamination at 1-9 days (first stage) and 10-21 days (second phase)
were affected by cold stress (P < 0.001). Cold stress also had a significant impact on the number of cull chicks; percent of
string navel, button navel, total string, and button; omphalitis; full body cavity; red hocks; dehydration; dirty chickens;
and stubby down. Cold stress affects performance during incubation and overall chick quality.
Key words: Cold stress, egg transportation, hatchability, chick quality, malposition and deformity, culls, egg weight loss,
embryo mortality and contamination
Introduction
Incubation provides proper conditions for fertile eggs
to produce high quality day old chicks. This occurs
when the fertile eggs are delivered under standard
conditions from breeder farm to hatchery (1,2). It is
necessary to protect hatching eggs against any heat
or cold stress during collection in the barn; storage
at the farm; and transportation to the hatchery, egg
grading room, incubator, and hatcher. For example,
Cobb-Vantress, Inc—one of the primary breeders—
* E-mail: ahmad.salahi2010@gmail.com
159
Effects of cold stress during transportation on hatchability and chick quality of broiler breeder eggs
recommends that the temperature of trucks delivering
hatching eggs from farm to hatchery be between 20
and 23 °C (3).
Temperature is one of the important factors
affecting the growth and development of the embryo
at all stages of the incubation period. The optimum
temperature for fertile eggs during the storage period
depends on the age of eggs, the age of broiler breeder
flock, and the genetic strain of the birds (1-4). It must
be noted that, as storage time increases, hatching eggs
should be stored at lower temperatures. Guidelines
are provided by primary breeder companies. For
instance, Aviagen recommends storing eggs 1-3
days or older (e.g., 4 days) at 19 °C and 16-18 °C,
respectively (5).
It has been shown that storing eggs at −18.33 °C
for 10 h reduced the internal temperature of the eggs
to −1 °C. However, this did not have any impact on
hatchability rate (6). Storing turkey hatching eggs at
−18.33 °C for 1, 2, 3, and 4 h led to a higher number
of female embryos compared to eggs stored from 10
to 12.7 °C; when the temperature was reduced to −16
°C, hatchability decreased (7). If the temperature of
the egg center over 120 min reaches −7 to −10 °C,
embryos will develop normally until they reach 8 days
of age (6). Keeping eggs at −3 °C for 4 days resulted
in the development of the embryos to the blood ring
stage—with a wide and enlarged blastoderm—after
which only the ectoderm and endoderm had the
opportunity to grow (6). Wilson (8) showed that cold
stress (−2 °C) before incubation increased embryo
mortality, and the peak of mortality occurred after 16
days. Lundy (9) showed that eggs maintained at −2
to −3 °C caused ice crystal formation, which led to
irreversible damage to embryo tissues.
Deeming (10) reported that cold stress reduced yolk
consumption by the embryo. It also prevented growth
of the embryo and reduced the water loss or vapor
exchange of the egg surface. A reduction of ambient
temperature in broiler breeder hens increased food
consumption and serum corticosterone. It reduced
egg production; feed efficiency; and concentrations
of some vitamins, minerals, insulin, ascorbic acid,
alpha tocopherol, and retinol in plasma. However,
the level of malondialdehyde; the production rate
of free radicals; and requirements for vitamins A, C,
and E increased (11-14).
160
Cold stress caused weakness in lymphoid organs
and decreased immune function in hens. The effects
of cold stress in chickens can be produced by different
mechanisms. The cold changes the endocrine
system; the hypothalamus-pituitary-adrenal axis,
sympathetic-adrenal-medullary axis, and the
thypothalamus-pituitary-thyroid axis become active,
and, as a result, hormone responses to stress will
be evident. Cold stress caused a significant drop in
corticosterone levels and affected cellular immunity,
but had no effect on T4 (15).
Several climate changes may take place during
egg transportation. From an economic perspective it
is a very important issue for day old chick producers.
Therefore, in the current study the effects of cold
stress and freezing conditions on broiler breeder eggs
during transportation, and subsequent chick quality
and incubation characteristics were investigated.
Material and methods
The altitude of Tehran Province, where the
experiment was carried out, is 972 m. The experiment
started in January, when the ambient temperature
during delivery of the hatching eggs to the hatchery
was about −15 °C. Due to road closures as a result of
cold weather conditions, all eggs were kept inside the
truck for 40 h. Internal temperature of the eggs was
measured by thermometer (in 144 eggs, by breaking
the eggs and measuring the temperature at the large
end). The thermometer (Testo, Co.) was capable of
measuring temperatures from −40 to 230 °C, with
accuracy to 0.1 °C. Temperature recording for each
egg took about 90 s. We did our best to minimize the
effect of ambient temperature on the thermometer.
A total of 72,000 fertile and settable eggs were used
in this study. Of this total number, 12% (equal to 48
cartons) were selected; 3 eggs from each carton. In
total, the internal temperatures of 144 eggs (48 × 3)
were measured.
There were a total of 4 treatments (temperature
group) −1.2 °C, 1 to 2 °C, 2.5 to 3.9 °C, 4 to 6 °C,
and a control group, 21-22 °C. Each treatment had
3 replicates, and each replicate contained 4800 eggs
(equivalent to a Petersime trolley). Each treatment
had 14,400 eggs in total. In a completely randomized
design, eggs were evaluated after 11 h prewarming
A. SALAHI, M. MOOSANEZHAD KHABISI, A. PAKDEL, A. BAGHBANZADEH
and then set in the incubator. From each treatment
720 eggs (3600 eggs total) were individually weighed
by digital scale (Berlini, model KV 2001).
Egg prewarming or preheating was completed in
11 h which is 2 h more than the usual time allotted.
In order to synchronize and prevent delay in the
removal of chicks from the hatcher, the egg setting
was changed to 1 h earlier than the usual time. Every
effort was made to prevent eggs from sweating while
they were still in the preheating room.
Eggs were individually weighed while in the setter
and at the time of transfer from setter trays to the
hatcher, at day 19 of incubation (19 days plus 6 h). In
the incubator, eggs usually lose part of their weight
as water vapor (egg weight loss) (4). To calculate the
percentage of egg weight loss, the following formula
Egg wrt pre – Egg wk trans
was used:
# 100
Egg wt pre
wt = weight; pre = at beginning of prewarming;
trans = transfer day.
It must be noted that we calculated prewarming
weight and not setting weight, as there might have
been some weight loss during the 8 to 11 h of
prewarming. In order to determine fertility, we
candled the eggs at day 18 of incubation. CobbVanress, Inc. recommends candling between days
10 and 12 of incubation (3); however, the Aviagen
management guide indicates that the right time for
candling is day 18 of incubation (5).
Measuring chick length is a fast method for
evaluating chick quality (16). We measured from
the beginning of the beak to the end of the middle
toe by ruler. Chicks were stretched along a ruler by
HatchTech method (16). According to Molenaar
(16), only 25 chicks are needed to measure length;
however, we evaluated 150 chicks. We calculated the
chick yield (%) or chick weight/initial egg weight
ratio from this formula (4):
Chick weight (g)
# 100
Initial egg weight (2)
We also performed an egg breakout on unhatched
eggs (equivalent 20.83% of total), and results were
recorded and evaluated. After the hatch, all residue,
dead embryos, debris, culls, and shells were collected
in order to prepare them for the production of
hatchery waste. During this process, the abovementioned materials are heated to 200 °C for 5 to
6 h in the processing tank, and the end product is
milled into hatchery waste (hatchery by product).
All data were analyzed with SAS software version
9.1. Statistical models used for data analysis were as
follows (17):
Yij = μ + Ti + Eij
Yij = observation ij
μ = mean of observations (overall mean)
Ti = effect of i treatment [i = 1, −1.2 °C, i = 2, 1
to 2 °C, i= 3, 2.5 to 3.9 °C, i= 4, 4 to 6 °C, and i = 5,
control (21 to 22 °C)] Eij = experimental error
Results
Our data showed that the rate of egg weight loss
during transportation from farm to hatchery was
1.49%. It must be mentioned that the ambient
temperature during transport from broiler breeder
farm to the hatchery reached below zero. This did not
cause freezing in the egg yolks or albumen; however,
wrinkling of the vitelline membrane and color spots
in egg yolks (manifested as darker or lighter areas)
were observed. In this study egg weight loss was
affected by temperature (P < 0.001), and maximum
weight loss (14.20%) was found in treatment 2. A
number of contaminated eggs exploded during the
transfer stage or incubation. In this study, percentage
of exploded eggs was influenced by temperature (P
< 0.01); most exploders (0.05%) were in treatment 1.
The number of early hatched chicks in the incubator
was significantly higher in treatment 1 (P < 0.001)
than in other treatments. Some chicks pipped the
outer shell of the egg while still in the incubator. Under
normal conditions we observed 1%-1.5% of eggs in
this situation. As indicated in Table 1, cold stress did
not have a significant effect on eggs pipped. The effect
of cold stress on chick weight was significant (P <
0.01), and mean weight of chicks in treatment 1 (−1.2
°C) was higher than in other treatments. Moreover,
chick yield in treatment 1 was higher than in other
treatments (P < 0.01). Chick length was affected by
cold stress (P < 0.001); minimum chick length (17.90
cm) was observed in treatment 1, and the greatest
chick length was found in the control group. Chick
length decreased with reduction in temperature
during transport.
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Effects of cold stress during transportation on hatchability and chick quality of broiler breeder eggs
Table 1. Effect of cold stress on performance and chick quality.
Initial egg
weight (g)
Egg weight
loss (%)
Exploder
(%)
1
61.76
13.66a
0.056a
0.016a
0.66ab
42.83a
17.90c
69.35a
2
61.80
14.20a
0.015b
0.0066b
1.206a
41.67b
17.98c
67.43bc
3
61.77
13.52a
0.015b
0.00c
1.14a
41.53b
18.07c
67.23bc
4
61.83
14.06a
0.023b
0.0046bc
1.19a
41.34b
18.30b
66.86c
Control
61.71
12.16b
0.020b
0.00c
0.02b
41.93b
18.61a
67.95b
SEM
0.187
0.222
0.0053
0.002
0.292
0.210
0.079
0.291
P value
0.992
0.0005
0.0012
0.0007
0.0674
0.0042
0.0002
0.0011
Treatment
Early hatched Egg pipped Chick weight Chick length
(%)
(%)
(g)
(cm)
Chick yield
(%)
a-c
: Means within a column without a common superscript differ significantly (P ≤ 0.05).
Treatments: 1 = (−1.2 °C), 2 = (1 to 2 °C), 3 = (2.5 to 3.9 °C), 4 = (4 to 6 °C), control =) 21 to 22 °C).
As shown in Table 2, hatchability and hatch of
fertile eggs decreased as the severity of cold stress
increased. Cold stress had a significant effect on
percent hatchability and hatch of fertile eggs (P <
0.001). Cull percentage and hatchery byproduct
efficiency increased when temperature was reduced
(P < 0.001); cold stress also significantly reduced the
percentage of chick weight uniformity (P < 0.01).
As presented in Table 3, increase in cold stress
before incubation resulted in a significant increase in
the rate of contamination (P < 0.001). Cold stress also
affected total embryo mortality (P < 0.001), and, with
decrease in temperature below 4 °C, total mortality
increased. Reducing the temperature did not affect
the infertility rate of eggs. Ectopic viscera (ECV) is a
condition in which the intestines appear outside the
abdominal cavity when the chicken is fully developed
(4). In this study, cold stress significantly affected the
incidence of ECV (P < 0.001); with a decrease in
temperature, the rate of ECV increased.
As shown in Table 4, most malpositions (1.10%)
were observed in treatment 1. It seemed that
temperatures below 2 °C increased the incidence
of malpositions. Total malpositions and also head
between thighs, beak above right wing, and head
under left wing increased. Cold stress caused a
Table 2. Effect of cold stress on hatchability, culls, uniformity, fertility, hatchery by product efficiency.
Hatchability
(%)
Hatch of fertile
(%)
Culls
(%)
Uniformity of chick
weight (%)
Fertility
(%)
Hatchery by product
efficiency (%)
1
85.40e
87.31d
1.84a
73.63d
97.81
51.35a
2
86.39d
88.28c
1.49b
77.57cd
97.85
51.19ab
3
86.85c
88.72c
1.21c
80.36bc
97.89
51.02bc
4
87.84b
89.86b
1.09d
82.50ab
97.75
50.96c
Control
90.36a
92.58a
0.84e
85.33a
97.60
50.30c
SEM
0.095
0.219
0.029
1.400
0.250
0.070
<0.0001
<0.0001
<0.0001
0.0014
0.9262
<0.0001
Treatment
P value
a– c
Means within a column without a common superscript differ significantly (P ≤ 0.05).
(Treatments: 1 = (–1.2 °C), 2 = (1 to 2 °C), 3 = (2.5 to 3.9 °C), 4 = (4 to 6 °C), control =) 21 to 22 °C)
162
A. SALAHI, M. MOOSANEZHAD KHABISI, A. PAKDEL, A. BAGHBANZADEH
Table 3. Effect of cold stress on infertility, embryo mortality, and contamination.
Contamination
Infertility
1-8 days
(early
mortality)
9-17 days
(middle
mortality)
18-19 days
(turned
mortality)
20-21 days
(late
mortality)
Total
mortality
1
2.19
6.15a
2.20a
1.53b
0.88a
2
2.14
5.24b
1.78c
2.02ab
3
2.10
5.47b
2.01b
4
2.25
4.39c
Control
2.40
SEM
P value
Treatment
Ectopic
viscera
1-9
days
(early)
10-21
days
(late)
10.77a
1.21a
1.21a
0.28a
0.85b
9.90b
1.10b
0.73b
0.17b
2.60a
0.84b
10.94a
1.00c
0.66c
0.13c
1.08d
2.59a
0.81c
8.87c
0.58d
0.67c
0.09d
3.48d
0.87e
1.86b
0.78d
7.00d
0.24e
0.12d
0.04e
0.250
0.149
0.043
0.179
0.005
0.130
0.019
0.006
0
0.9262
<0.0001
<0.0001
0.0065
<0.0001
<0.0001
<0.0001
<0.0001
< 0.0001
a– c
Means within a column without a common superscript differ significantly (P ≤ 0.05).
(Treatments: 1 = (–1.2 °C), 2 = (1 to 2 °C), 3 = (2.5 to 3.9 °C), 4 = (4 to 6 °C), control =) 21 to 22 °C)
Table 4. Effect of cold stress on embryo malposition.
Malposition
Head between
thighs
Head in the small
end of egg
Head under
left wing
Head not directed
toward air cell
Beak above
right wing
TOTAL
1
0.39a
0.15c
0.06b
0b
0.50a
1.10a
2
0.22b
0.48b
0.00d
0b
0.37b
1.07a
3
0.22
b
b
b
0
b
0.13
c
0.89b
4
0.17c
0.58a
0.12a
0.02a
0.00d
0.89b
d
c
c
d
Treatment
Control
SEM
P value
0.06
0.48
0.16
0.06
b
0.04
0
0.00
0.26c
0
0.015
0
0
0
0.015
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
a– c
Means within a column without a common superscript differ significantly (P ≤ 0.05).
(Treatments: 1 = (–1.2 °C), 2 = (1 to 2 °C), 3 = (2.5 to 3.9 °C), 4 = (4 to 6 °C), control =) 21 to 22 °C)
significant increase in the rate of malpositions in
treatments compared to the control group (P < 0.001).
As indicated in Table 5, cold stress caused
significant increases in the incidence of chicken
deformities in treatments compared to the control
group.
As shown in Table 6, cold stress significantly
increased the number of chicks culled due to
conditions such as red hocks, button navel,
summation of button, and string navel.
Discussion
The vitelline membrane contains many proteins,
carbohydrates, and lipids. Eggs stored for 6 months
at temperatures ±1 °C experience weight loss, loss of
nitrogen, and changes in the chemical composition
of vitelline (18). The vitelline membrane loses its
natural state (selective nature) between 20 and 30
days of storage (19). After 6 weeks eggs stored at 4
°C showed a decrease in the elastic properties of the
vitelline membrane; this resulted in problems that
163
Effects of cold stress during transportation on hatchability and chick quality of broiler breeder eggs
Table 5. Effect of cold stress on embryo deformity and disorders.
Treatment
Deformity
TOTAL
Exposed brain
Without eye(s)
4 legs
Deformed beak
1
0.22a
0c
0.13a
0.90c
1.25c
2
0.11c
0.40b
0.05ab
2.48a
3.04b
3
0.09d
0c
ob
0d
0.06d
4
0.13b
1.33a
ob
2.36b
3.82a
Control
0.02e
0c
ob
0d
0.02d
0
0.007
0.03
0
0.033
<0.0001
<0.0001
0.0396
<0.0001
<0.0001
SEM
P value
a– c
Means within a column without a common superscript differ significantly (P ≤ 0.05).
(Treatments: 1 = (–1.2 °C), 2 = (1 to 2 °C), 3 = (2.5 to 3.9 °C), 4 = (4 to 6 °C), control =) 21 to 22 °C)
Table 6. Effect of cold stress on culled chicks.
Culls and deaths
Treatment
String navel
e
Button navel
a
String + button Body cavity full
a
d
Red hock
3.15a
4.99d
12.98c
2.49b
0d
5.10c
0e
0c
62.63b
1c
4.53e
17.37a
0c
7d
61.56c
1.43b
11a
16b
0c
0.264
0.292
0.323
0.133
0
0.082
0.038
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
1.77
20.79
22.56
58.09
4.29
2
6.27c
12.79b
19.07b
56.29e
4.18a
3
12.53b
6c
18.53b
76.36a
4
14.47a
0e
14.47c
5d
2d
0.172
<0.0001
SEM
P value
7.82
b
Stubby down Dirty chicks
4.08d
1
Control
Dehydrated
a
a– c
Means within a column without a common superscript differ significantly (P ≤ 0.05).
(Treatments: 1 = (–1.2 °C), 2 = (1 to 2 °C), 3 = (2.5 to 3.9 °C), 4 = (4 to 6 °C), control =) 21 to 22 °C)
facilitated the rupture of the vitelline membrane
(20). Storage time and temperature are 2 factors that
affect the vitelline membrane. The strength of the
vitelline membrane decreases with increasing storage
time. This may allow nutrients in the yolk to become
available to any microorganism present in the
albumen (21). Wrinkling of the vitelline membrane
in sub-zero temperatures, under cold stress, is in line
with this finding.
Egg water loss during storage has a positive effect
on hatchability (22). The percentage of egg weight
loss between 1 and 19 days in Cobb 500 and Ross
164
308 strains is 10.9% and 12.9%, respectively. Age of
the flock (before 44 weeks) does not affect egg weight
loss, but the effect of strain is significant (23). Egg
weight loss reaches 12% up to 18 days, and as the
altitude increases, the drop in egg weight increases
(3). According to Aviagen, egg weight loss should
be 12% from the time eggs set in the incubator up
to transfer; under these conditions hatchability and
chick quality are ideal. If eggs are stored for more
than 6 days, egg weight loss will reach 11.5% (4).
In the current study, egg weight loss in control eggs
was 12.16%, which conforms to the observations of
A. SALAHI, M. MOOSANEZHAD KHABISI, A. PAKDEL, A. BAGHBANZADEH
Aviagen and Cobb-Vantress. When compared with
the control group, cold stress caused an increase
in the egg weight loss. However, there was not a
significant difference between the treatments.
An increase in exploder eggs can be caused by
a dirty nest, egg laying on the floor, egg washing,
using dirty egg cleaner or sandpaper, high levels of
dust in the nest, transportation and cold conditions,
sweating eggs, spraying water on eggs, broken eggs,
hand contamination of egg handlers, contamination
of the setter floor, air filters, and the moisture supply
system (24). The current study demonstrated that
cold stress is another factor affecting the percentage
of exploder eggs.
Early hatch in the incubator can be attributed
to small eggs, differences between breeds, as well as
high temperatures and low humidity in the incubator
(24). In the present study, cold stress—especially at
temperatures below zero—increased the rate of early
hatched chicks.
Chick weight is affected by egg weight (25,26).
A decrease in temperature (from 37.8 to 36.6 °C)
during incubation resulted in an increase in chick
body weight, from 39 to 40 g, and yolk sac weight,
from 3 to 4.3 g (27). These findings are consistent
with the findings of others; there were overweight
chicks in treatment 1 and a lack of yolk uptake and
inappropriate yolk usage.
Chick yield or chick weight-to-egg ratios are
normally between 66% and 68% (3). This ratio in
fresh eggs (stored for a short period of time) was
between 67% and 67.5% (4). Other research reported
chick yield at 36 weeks at 73.1% (23). In the current
study, the chick weight-to-egg ratio was higher in
treatment 1. Improper use of nutrients inside the egg
and yolk sac prevents chicks from growing enough.
A temperature decrease from 37.8 to 36.6 °C during
incubation reduced chick length from 16.8 to 16.3
cm (27). Chick length in this experiment was affected
by cold stress; reducing the temperature during
transport also reduced chick size.
Percentage hatchability and hatch of fertile eggs
(Ross 308, 36 weeks of age) were 80.8% and 85.9%,
respectively (23). A temperature decrease from
37.8 to 36.6 °C in incubation caused a reduction in
hatchability (salable chicks) from 87% to 81% (27).
In the current study, reducing the temperature level
reduced the hatch of fertile eggs and hatchability. The
rate of cull chicks was 0.97%. Although it was 0.68%
at 38 weeks and 0.42%-0.67% at under 43 weeks of
age, the highest rate was 1.49% at 63 weeks (Cobb
500) (28). In the current study, the percentage of
cull chicks and hatchery byproduct (hatchery waste)
increased as the temperature was reduced.
Uniformity of flock is the percentage of chicks
within ±10% (29) or ±15% (3) of the average body
weight at a certain age. The goal is 80% uniformity
in a flock. Uniformity is affected by many factors
including egg size, shell quality, genetic variation
of parents, flock density, quantity or quality of feed
consumed, parasites, environmental conditions (nest
temperature), photoperiod programs, feed restriction
programs, broiler breeder body weight (30),
incubator type or model (single stage or multistage),
incubation conditions, duration of egg storage, initial
egg weight, chick room conditions, condition of
trucks and transportation system, variation between
eggs (non-uniform chicks produced from small or
large eggs), mixing eggs from young and old flocks,
mixing eggs from different strains, storage periods,
different patterns of egg storage, ventilation, nonuniform setter and hatcher conditions, diseases, and
stress (24). Hatchability in flocks with 55%-59% and
75%-80% uniformity was 69.19 ± 1.93% and 83.93 ±
1.65%, respectively (30). In the current study, cold
stress severely reduced uniformity of body weight.
Egg contamination rates from 0 to 21 days
(in a flock 31-45 weeks of age) were nearly 0.5%
(4). Placing cold stress on eggs before incubation
significantly increased the number of contaminated
eggs and chicks with full body cavity.
Cold stress had a significant effect on total
embryonic mortality, and with reduction in
temperature (below 4 °C) the rate of mortality
increased. Reducing the temperature did not
affect infertility. Egg shell contamination, nest
contamination, ventilation status, and hatchery
disinfection can cause increases in embryo
mortality (31). An increase in the duration of egg
storage, fumigation within 12 to 16 h of incubation,
high or low temperatures, egg damage during
transportation (jarring), illness, an old or aging flock,
contamination, drugs, and pesticides are factors
165
Effects of cold stress during transportation on hatchability and chick quality of broiler breeder eggs
that can increase embryonic mortality (24). Early
embryonic mortality (36 weeks, Ross 308) was 2.5%
(23). A decrease in incubator temperature from 37.8
to 36.6 °C increased early embryonic mortality from
2.7% to 2.8% (27). Mortality at 12-17 days is caused
by inappropriate incubator temperature, moisture,
nutritional deficiency (vitamins, phosphorus, and
linoleic acid), and lethal genes (24). Reduction in
incubator temperature from 37.8 to 36.6 °C increased
embryonic mortality at the middle stage from 0.2% to
0.5% (27). Embryo mortality in the middle stage (36
weeks, Ross 308) was 3% (23). Wilson (25) showed
that cold stress (−2 °C) before the incubation period
increased embryo mortality and most mortality
reported after the 16th day. In the current study, we
found that early stage embryo mortality in treatment
1 was higher than in other treatments.
.
Eggshell pipping can result from upside-down
eggs, setting fumigation at a high concentration,
high temperature, high humidity, low turning, old
eggs, large-sized eggs, and ventilation problems (24).
Embryo mortality at the end of incubation (late stage)
in a 36 week Ross 308 was 1.1% (23).
A reduction in incubator temperature from 37.8
to 36.6 °C increased embryonic mortality at the
pipping stage (beak entering air cell) from 0.8% to
1.4% and at external pipping (tip of beak puncturing
the eggshell) from 0.9% to 2.4% (27). The incidence
of ECV is increased by high incubator temperatures,
inheritance, and lethal genes (24). In the current
study, cold stress significantly increased ECV rates.
The quality of chickens during incubation depends
on various factors such as maternal age, flock
status, length of storage and storage conditions, and
incubation conditions (32). Inside the egg a normal
embryo must position itself with the head (beak)
under the right wing and placed directly into the air
cell. Usually 1%-2% of chickens have malpositions
and deformity, and these disorders are observed in
the last week of incubation. In this study, malpositions
occurred in 1.2%-1.8% of chicks (average 1.5%). Most
embryos have a type of malposition that prevents the
use of oxygen and they die in the shell (dead in shell);
only a few of these embryos are able to leave the shell.
Type 6 malpositions account for 48% of malpositions
(beak above right wing); type 5 (feet on the head),
20%; type 1 (head between the thighs), 12.5%; type 2
166
(head towards the end thin egg), 7.5%; type 3 (head
under left wing), 7.5%; and type 4 (head not directed
toward air cell), 4.5% (33).
Cold stress significantly affected total
malpositions. Most malpositions (1.10%) occurred
in treatment 1. A decrease in temperature towards
−2 °C increased the incidence of malpositions. One
of the important factors affecting the occurrence of
malpositions is insufficient egg weight loss in the
incubator (33). In the present study, the rate of egg
weight loss in all treatments was higher than in the
control group and the total rate of malposition was
associated with it.
Deformity or abnormalities prevent embryos
from leaving the eggs. The rate of deformity was
0.22%-0.3%. Most abnormalities occur between 15
and 21 days of incubation and include brain hernia
(29%), beak deformity (27%), failure to develop
eyes (25%), 4 legs (10%), lack of upper beak (8%),
and twisted legs (1%). High incubation temperatures
cause abnormalities in the brain and eyes, while
low temperatures affect chicken growth. At normal
hatchability status (85%) the rate of deformity does
not exceed more than 0.3% (33).
In our experiment, cold stress caused a significant
increase in the rate of deformity in treatment groups
compared to the control. Inheritance and viral
infection cause cross beaked chickens and chickens
without eye(s); these and other malformations
are also caused by high temperatures, problems
in egg handling, or delay in hatch time due to low
temperatures during incubation (3). We observed
that cold stress increased dirty chicks, red hock,
button navel, and total string and button navel.
In conclusion, cold stress during the delivery of
eggs from farm to hatchery affects the performance
of the developing embryo during incubation; cold
stress also impacts chick quality at the time of hatch
and at later stages of life.
Acknowledgement
We would like to thank the manager and personnel at
Mahan Hatchery.
A. SALAHI, M. MOOSANEZHAD KHABISI, A. PAKDEL, A. BAGHBANZADEH
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