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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 211 Efect of Photoperiods and Stocking Densities on Broilers
INTRODUCTION
High stocking densities and long lighting periods are two
major environmental factors common to broiler production
(1). Te control of these factors at an optimum level not only
increases commercial proftability, but also contributes to se-
curing the supply of the human population with adequate
food and animal protein. When determining stocking densi-
ty, producers should take multiple factors into consideration,
which include among others, the size of the broiler chickens,
the area occupied by feeders and drinkers, the area of the pen
the animals are raised in, animal welfare standards, animal
nutrition, fattening performance and economic return (2).
Despite its negative impact on the individual performance of
bird’s high stocking density remains a primary preference of
broiler producers and is still considered appealing in terms of
proftability (3, 4). Although no consensus has been reached
on the optimum stocking density, research conducted to date
suggests a maximum body weight of 30 kg per square meter
(5). It is known that as the stocking density increases the fat-
tening performance varies, yet, previous studies have reported
variable fndings on the direction and strength of such efects
(6). To exemplify, while some researchers have reported that
Te Efect of Diferent Photoperiods and Stocking Densities on
Fattening Performance, Carcass and Some Stress Parameters in Broilers
Das, H.
1
and Lacin, E.
2
1
Vocational High School, Department of Veterinary, Gumushane University, TR-29100 Gumushane, Turkey.
2
Department of Animal Science, Faculty of Veterinary Medicine, Atatürk University, TR-25240 Erzurum, Turkey.
*
Corresponding Author: Assoc. Prof. Dr. Ekrem Lacin, Department of Animal Science, Faculty of Veterinary Medicine, Atatürk University, 25240, Yakutiye,
Erzurum, Turkey. Tel: +90 442 236 08 80, Fax: +90 442 236 08 81, Email: ekremlacin@hotmail.com, elacin@atauni.edu.tr
ABSTRACT
Tis study was carried out for the purpose of investigating the efects of diferent photoperiods and stocking
densities on physiologic parameters such as body weight, feed consumption, feed efciency, carcass traits
and some stress parameters in broiler chickens. Troughout the experiment, 480 day-old male chickens
obtained from a commercial hatchery were used. Te chicks were placed in diferent partitions which
had three diferent photoperiod (continuous lighting: 24 hour light, constant lighting: 16 hour light - 8
hour dark, intermittent lighting: 4 hour light – 2 hour dark) were applied. Each photoperiod group was
formed with fve replicates at two diferent stocking densities (normal stocking density: 12 broiler/m
2
, high
stocking density: 20 broiler/m
2
). Te experiment was carried for 42 days. At the end of the experiment, the
efect of photoperiod and stocking density on live weight gain were signifcant (P<0.05) while photoperiod
signifcantly afected the feed consumption only (P<0.05). Te feed efciency were insignifcant (P>0.05)
with respect to both factors. Te photoperiod programs had signifcant efects on the relative weight of
gizzard, blood, feather percentage values (P<0.05) and breast percentage values (P<0.01). Te stocking
density has a signifcant efect on relative heart weight (P<0.05) and entire thigh values (P<0.01). At the end
of the experiment, it was ascertained that the photoperiod program and stocking density had no signifcant
(P>0.05) diference on tonic immobility and tibial dyschondroplasia values. However, stocking density had
a highly signifcant efect (P<0.01) on gait score values and on heterophil-lymphocyte rate values (P<0.01).
Keywords: Broiler; Performance; Carcass Traits; Stress; Leg health.
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 Das, H. 212
high stocking density is associated with decreased fnal body
weight (3, 7), others have indicated no change in body weight
(8, 9).
A second major factor infuencing the fattening perfor-
mance of broiler chickens is the lighting period (10). Te
lighting period is adjusted according to the age and growth
conditions of the animals. During production, it is foreseen
that broiler chickens are exposed to a daily dark period of
at least 4 hours, however, during the growth period and the
rest period the animals needs may exceed this time length
(11).Te results are contradictory for various parameters af-
fected by photoperiod. For example, reports (12) indicate
that continuous lighting is associated with increased feed
consumption and some others point out to no diference (13)
or decrease (14) being observed in feed consumption. Some
studies reported reduced feed conversion (12, 14) and oth-
ers suggested no change in feed conversion rates when such
lighting programs are applied (15). Tese efects need to be
clarifed with further research.
For these reasons, this study was carried out for the pur-
pose of investigating the efects of diferent photoperiods and
stocking densities on physiologic and some stress parameters
in broiler chickens.
MATERIAL AND METHODS
Birds and husbandry
Te Research Animal Ethic Committee of Atatürk University
permitted the performance of this experiment. Te present
study was conducted at the poultry unit of the Research Farm
of Atatürk University, Faculty of Veterinary Medicine. Four
hundred and eighty day-old male Ross-308 broiler chicks
constituted the material of the study. Te animals includ-
ed in the experimental groups were given feed and water
ad libitum, and the broiler chick ration (Bayramoğlu Yem,
Erzurum, Turkey) given between weeks 0-3 contained 24%
of crude protein and 3075 kcal/metabolic energy/kg, while
the broiler chicken ration given between weeks 3-6 contained
20% of crude protein and 3200 kcal/ metabolic energy /kg.
Experimental design
In three diferent experiment windowless rooms, lighted only
by fuorescent lights, from day 7, the chicks were randomly
allocated to 1.0 x 1.0 meter pens, the foor of which was
covered with 10 cm layer of wood shavings, such that fve
replicates of the two diferent stocking densities given below
were applied in each room with a number of 10 chambers
per room and a total of 30 chambers. Mechanical ventilation
was performed. Te average pen temperature was 32±1˚C in
the frst week and was then gradually lowered to an average
of 24±2˚C.
Study design
Te stocking densities applied were as follows:
a) Normal stocking density (NSD): 12 broilers/m
2
b) High stocking density (HSD): 20 broilers/m
2
Te animals were assigned to 24 hours of continuous
lighting in Room 1 (CSL), a constant lighting schedule of
16 hours of light and 8 hours of dark in Room 2 (CTL), and
an intermittent lighting schedule based on a 4-time repeated
daily exposure to 4 hours of light and 2 hours of dark in
Room 3 (IL).
Calculation of the performance values
Te chickens were weighed in all groups on days 7, 14, 21, 28
and 35 of the experiment for the calculation of mean body
weights and daily, weekly and cumulative body weight gains.
Te weekly feed consumption of the groups was determined
by subtracting the amount of feed remaining in the feeders
of each group on days 14, 21, 28, 35 and 42 from the total
amount of feed provided to each group per week. Weekly and
cumulative feed conversion rates were calculated by dividing
feed consumption by body weight gain.
Mortalities were recorded on a daily basis. Percentile sur-
vival was calculated by dividing the number of surviving birds
by the total number of birds included in the experimental
group. Variation coefcients related to uniformity was as-
sessed by individually weighing each chicken on day 42 of
the experiment; the standard deviation was divided into the
mean body weights of the experimental groups.
Determination of the carcass traits
At the end of the experiment, 2 chickens from each group
and in total 60 broiler chickens were slaughtered and cut into
carcass parts as described by Aksu and Imik (16) and were
weighed. Te carcass parts and viscera were proportioned to
the carcass weight for the calculation of carcass yield and
percentages. Te broiler chickens selected for slaughter were
fasted for 8 h prior to slaughter to ensure that their digestive
tract was emptied. Subsequently the birds were eviscerated
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 213 Efect of Photoperiods and Stocking Densities on Broilers
manually, washed and allowed to drain for 10 min (17). After
evisceration, carcasses were stored at 3±0.5 °C for 24 h. Te
carcasses were dissected as described by Barbut (18).
Determination of tonic immobility (TI)
On day 40, the chickens were caught avoiding any harm and
were transferred to a silent room, where they were restrained
on their back in a cradle like U-shaped apparatus to deter-
mine tonic immobility (TI) periods as described by Jones
and Faure (19).
Determination of gait score (GS)
With an aim to determine the gait score (GS), on day 41 of
the experiment, each chicken was taken out of its cage and
allowed to walk alone along the passageway for observation.
Tose reluctant to move were gently prodded. Scoring was
made from “0” to “5” as described by Kestin et al., (20). “0”
indicates walking smoothly while “5” shows the inability to
walk at all.
Determination of tibialdyschondroplasia (TD)
At the end of the experiment, two chickens from each sub-
group were sacrifced and in each of these birds the longitu-
dinal section of the left tibial bone extending to the epiphy-
sis was assessed for tibial dyschondroplasia (TD) (21). Te
measurement of the lesions was performed using a millimeter
calliper. Te severity of TD was scored as “0” in the case of
the non-existence of lesions, “1” in cases where the size of the
area of the lesion extending distally was smaller than 0.5 cm;
“2” when the size of this area ranged from 0.5 to 1 cm and
“3” when this area was larger than 1 cm.
Determination of the heterophil/lymphocyte ratio
With an aim to determine the heterophil to lymphocyte ratio
(H/L) blood smears were prepared from blood samples taken
from the wing vein (vena cut-in ulnaris) of the chickens on
day 39 of the experiment. After fxation in methyl alcohol,
these blood smears were stained with Giemsa and observed
under an immersion objective for the counting of 100 leu-
kocytes, using a light microscope at × 1,000 magnifcation.
Statistical analysis
Te experiment was arranged in a complete randomized
design. Two-way ANOVA was employed using the GLM
procedure and diferences among experimental groups for
the performance parameters as well as carcass parameters
were evaluated by Duncan’s multiple comparison test (SPSS
for Windows Release 10.01, SPSS Inc., 1996).
A two-way ANOVA was used to determine the interac-
tions between lighting programs and stocking densitywith
respect to the studied parameters. Diferences among the
experimental groups for survival rate, tibial dyschondroplasia
and gait score were assessed by means of the Kruskal-Wallis
test. Signifcance was considered at a probability of less than
or equal to 0.05. Te linear model used to test the efects of
experimental groups onparameters were as follows:
Y
ijk
= m+L
i
+SD
j
+(L´SD)
ij
+e
ijk
Where, Y
ijk
= response variable, m= population mean,
L
i
=lighting program (CSL, CTL, IL), SD
j
= stocking density
(NSD, HSD),(L´SD)
ij =
interactions between lighting pro-
grams and stocking density, e
ijk
= experimental error.
RESULTS
Performance
Te mean body weights (BW) measured (Figure 1) in the last
week of the experiment in groups CSL, CTL and IL were
2469.45±24.5 g, 2384.25±24.5 g and 2399.30±24.5 g, respec-
tively, and it was ascertained that the mean of the fnal body
weight of group CSL was signifcantly higher than that of
groups CTL and IL (P<0.05). Groups CTL and IL did not
display any signifcant diference from each other (P>0.05).
When assessed for body weight, group CSL displayed sig-
nifcantly higher values at weeks 2, 3, 4, and 5 compared to
the other experimental groups (P<0.01). Te comparison of
groups CTL and IL demonstrated that at week 2 group IL
exhibited values greater than that of group CTL, and during
the remaining experimental period, no signifcant diference
existed between the two groups (P>0.05).
Assessment for the body weights associated with stock-
ing density revealed that the mean body weight of the group
raised under normal stocking density was signifcantly higher
on day 42 (P<0.05) and more signifcantly higher on day 21
of the experiment (P<0.01). During the other weeks, stock-
ing density was not observed to have any signifcant efect
on the body weight of the birds.
Assessment of the interaction between lighting period
and stocking density revealed the presence of a statistical-
ly signifcant diference to have occurred in only the body
weight values measured at week 3 (P>0.05).
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 Das, H. 214
Figure1: Body weights (g) of the experimental groups. a, b, c showed
statistically diferences in groups of lighting period treatments (P value
are 0.005, 0.008, 0.004, 0.008, 0.043 in week 2, 3, 4, 5, 6 respectively)
and x, y showed diference in stocking density groups (P value are
0.004, 0.032 in week 2, 6 respectively).
Figure 2: Cumulative food consumption of the experimental groups.
a, b, c shows statistically diference in groups of lighting period
treatments (P value are 0.035, 0.028, 0.039 in week 1-3, 1- 5 and
1-6 respectively) and x,y shows diference in stocking density groups
(P value is 0.041 in week 1-6).
Figure 3: Cumulative feed conversion ratio in the experimental
groups. a, b, c shows statistically diference in groups of lighting period
treatments (P value is 0.023 in week 1-2) and x,y shows diference in
stocking density groups.
Figure 4: Coefcients of variation ratio relating to body weight in the
experimental groups (%).
Based on the measurements performed on days 21, 35
and 42 of the experiment, it was determined that the feed
consumption (FC) of group CL was signifcantly higher than
that of the other two groups (P<0.05) (Figure 2). When as-
sessed for stocking density, it was ascertained that the FC
of group NSD was signifcantly higher on days 21 and 35
(P<0.05). Te efect of the lighting period on feed conversion
rates (FCR) was observed on day 14 (Figure 3), while the
impact of interaction between stocking density and photope-
riod was only observed on day 21 (P<0.05). Stocking density
had no efect on FCR.
Te survival rate values in the experimental groups CSL,
CTL and IL were 97.50%, 97.85 and 95.85, respectively.
It was demonstrated that the efects of lighting period and
stocking density on survival rates were statistically insignif-
cant (P>0.05).
Coefcients of variation values relating to body weight
in the experimental groups are presented in Figure 4. Te
maximum variation was calculated in IL-NSD group while
the least variation was in CSL-NSD group.
Carcass traits
Te carcass traits of the birds are shown in Tables 1 and
Table 2. At the end of the experiment, signifcant difer-
ences were observed among the diferent lighting schedule
groups for gizzard, blood and feather percentages (P<0.05)
and higher signifcant diferences were observed for whole
breast percentages (P<0.01). Te percentage of the rela-
tive heart weight difered signifcantly (P<0.05) and the
percentage of entire relative thigh weight also difered sig-
nifcantly at a higher rate with stocking density (P<0.01).
Te interaction between the lighting period and stocking
density had a signifcant efect on the percentages of the
gizzard and heart relative weights (P<0.05) and signifcant
efect on the percentages of the head and neck relative
weights (P<0.01).
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 215 Efect of Photoperiods and Stocking Densities on Broilers
Tonic immobility
Mean TI periods of the groups are given in Figures 5. Te
efects of lighting period and stocking density alone and
the interaction of lighting period and stocking density on
the diferences observed between the experimental groups
for TI values were found to be statistically insignifcant
(P>0.05).
Tibial dyschondroplasia
Te TD scores determined for the groups after the sacrifce
of animals are presented in Figure 5. According to these re-
sults, the experimental groups did not difer from each other
for TD.
Gait score
Te GS of the experimental groups included in the present
study are given in Figure 5. Based on the gait scores, it was
determined that gait score were observed at a higher rate in
the group subjected to CSL, when compared to the other
two experimental groups.
Heterophil/lymphocyte ratio
Te mean blood cell counts determined in the experimen-
tal groups are shown in Table 3. According to the results
obtained, H/L ratios were afected by the lighting period
and stocking density. Te H/L ratio was signifcantly higher
in the group exposed to CSL, compared to the other two
groups (P<0.01).
Table 1: Te mean and standard error of means of the neck, blood, head, feather, foot and relative organ weights (%BW).
L SD Neck Blood Head Feather Tail Gizzard Liver Heart
CSL
NSD 5.77±0.02 4.34±0.12 2.52±0.05 5.52±0.11 1.10±1.18 2.14±0.17 1.30±0.05 0.55±0.02
HSD 4.93±0.02 4.05±0.12 2.78±0.05 5.28±0.11 1.18±1.18 1.98±0.17 1.90±0.05 0.72±0.02
CTL
NSD 5.39±0.02 3.55±0.12 2.72±0.05 4.83±0.11 1.18±1.18 2.23±0.17 1.96±0.05 0.62±0.02
HSD 5.84±0.02 3.58±0.12 2.72±0.05 4.79±0.11 1.42±1.18 2.37±0.17 1.95±0.05 0.57±0.02
IL
NSD 5.58±0.02 3.78±0.12 2.69±0.05 5.08±0.11 1.39±1.18 2.46±0.17 1.84±0.05 0.63±0.02
HSD 5.70±0.02 3.89±0.12 2.47±0.05 5.16±0.11 1.15±1.18 2.08±0.17 1.97±0.05 0.71±0.02
CSL 5.35±0.02 4.19
a
±0.90 2.65±0.05 5.40
a
±0.15 1.14±1.20 2.06
b
±0.09 1.84±0.06 0.63±0.02
CTL 5.62±0.02 3.57
b
±0.90 2.72±0.05 4.81
b
±0.15 1.30±1.20 2.30
a
±0.09 1.96±0.06 0.60±0.02
IL 5.64±0.02 3.83
b
±0.90 2.58±0.05 5.12
ab
±0.15 1.27±1.20 2.27
a
±0.09 1.91±0.06 0.67±0.02
NSD 5.58±0.02 3.89±0.02 2.64±0.04 5.15±0.25 1.22±1.23 2.28±0.07 1.86±0.02 0.60±0.03
HSD 5.49±0.02 3.84±0.02 2.66±0.04 5.08±0.25 1.25±1.23 2.14±0.07 1.94±0.02 0.67±0.03
L NS * NS * NS * NS NS
SD NS NS NS NS NS NS NS *
LxSD ** NS ** NS NS * NS *
L: Lighting programs; SD: Stocking density; CSL: Continuous lighting; CTL: Constant lighting; IL: Intermittent lighting; NSD: Normal stocking
density; HSD: High stocking density; NS: Not signifcant; L x SD: Interactions between lighting programs and stocking density; BW: Body weight;
*: P<0.05; **: P<0.01; a, b: Diferences between the means with diferent letters in same columns are signifcant.
Figure 5: Tonic immobility, tibial
dyschondroplasia and gait score values in
the experimental groups (P value denoting
variation in gait score is 0.025).
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 Das, H. 216
DISCUSSION
Performance
In the group exposed to CSL, high body weights were ob-
served at the end of the experiment resulting from the ani-
mals having had free access to feed and water due to lack of
daylight restriction. Findings previously reported by many
researchers are in agreement with these results (15, 22).
However, some studies have reported that CSL does not have
any efect on fnal body weight (15, 23). It was observed that
until the age of 14 days, exposure to an IL schedule resulted
in a greater body weight gain compared to that induced by a
CTL schedule. However, later, the preference of any of these
lighting schedules would not make any diference in terms of
body weight gain. Similarly, Ozkan et al., (23) have indicated
that the exposure of broiler chickens to a CTL in the early
growth period led to decreased body weight as a result of a
shortened lighting period.
According to these results, if we look with respect of
weight gain, CSL appears more appropriate. Te decreases
observed in the body weights of the chickens raised at a
high stocking density during the last week of the experi-
ment suggested that the tolerable level of body weight per
square meter was exceeded at the end of the 5
th
week with
negative impact on fattening performance. By the 5
th
week,
which was determined to be the breaking point of the ex-
periment, the body weights of the groups exposed to NSD
and HSD were ascertained as 21.12 kg/m
2
and 36.14 kg/
m
2
, respectively.
Based on these results, it may be suggested that the
maximum body weight per unit of area should be 36.14 kg/
m
2
. Other studies are available, which also suggest that high
stocking density decreases body weight (3, 7). Similar to the
present study, in an investigation conducted by Hassanein
(24), the negative efect of increased stocking density at
weeks 3 and 6 on body weight was found to be statistically
signifcant.
In contrast to the fndings obtained in the present study,
Onbasilaret al., (25) have reported that the efect of the in-
teraction between lighting period and stocking density on
the body weight of broiler chickens at weeks 3 and 6 was
statistically insignifcant (P>0.05).
Te present study demonstrated that neither stocking
density nor lighting period afected feed conversion, but in
the case of exposure to CSL, higher body weights were ob-
served as a result of increased feed consumption. Apart from
studies suggesting that exposure to CSL does not alter feed
conversion rates (15), there are also studies reporting feed
conversion rates to be slightly afected with CSL (14, 15).
Studies are also available, which in agreement with this ex-
periment, indicate that neither feed consumption nor feed
conversion rates were afected by stocking density (26, 27).
Table 2: Te mean and standard error of means of the carcass traits (%).
L SD Hot Carcass Yield (%BW) Cold Carcass Yield (%BW) Breast (%CC) Tigh (%CC) Wings (%CC)
CSL
NSD 73.57±1.33 72.88±1.27 45.04±1.13 39.48±2.50 11.15±0.26
HSD 74.55±1.33 74.02±1.27 44.48±1.13 41.17±2.50 11.34±0.26
CTL
NSD 74.89±1.33 74.04±1.27 43.09±1.13 39.16±2.50 11.29±0.26
HSD 74.14±1.33 73.31±1.27 41.72±1.13 41.03±2.50 11.57±0.26
IL
NSD 74.72±1.33 74.09±1.27 42.56±1.13 39.07±2.50 11.88±0.26
HSD 74.50±1.33 73.80±1.27 42.68±1.13 40.76±2.50 11.69±0.26
CSL 74.06±1.30 73.45±1.24 44.76
a
±1.12 40.33±2.45 11.25±0.23
CTL 74.52±1.30 73.67±1.24 42.41
b
±1.12 40.10±2.45 11.43±0.23
IL 74.61±1.30 73.95±1.24 42.62
b
±1.12 39.91±2.45 11.78±0.23
NSD 74.39±2.32 73.67±3.23 43.56±2.10 39.24±0.34 11.44±2.21
HSD 74.40±2.32 73.71±3.23 42.96±2.10 40.99±0.34 11.53±2.21
P<
L NS NS ** NS NS
SD NS NS NS ** NS
LxSD NS NS NS NS NS
L: Lighting programs; SD: Stocking density; CSL: Continuous lighting; CTL: Constant lighting; IL: Intermittent lighting; NSD: Normal stocking
density; HSD: High stocking density; NS: No signifcant; L x SD: Interactions between lighting programs and stocking density; BW: Body weight;
CC: Cold carcass; *: P<0.05; **: P<0.01; a, b: Diferences between the means with diferent letters in same columns are important.
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 217 Efect of Photoperiods and Stocking Densities on Broilers
Another literature report claimed that feed consumption de-
creases and feed conversion improvs with increased stocking
density (28). According to our results, it could be concluded
that feed efciency, an economically important trait is not
important in deciding on the stocking density in the presence
of sufcient feed.
It was ascertained that the lighting schedule and stocking
density had no impact on the mortality of the broilers. Te
highest uniformity on end experimental body weights was
observed in the CSL-NSD group, while values pertaining
to the other groups were observed to be close to each other.
Feddes et al.,(29) determined the body weight variation
coefcients of broiler groups housed at diferent stocking
densities (11.9, 14.3, 17.9, 23.8, broilers/m
2
) as 15.3, 13.4,
13.6, and 13.0, respectively. It was observed that, as stock-
ing density increased variation decreased. Tese numbers are
higher than our results. Furthermore, Classen (30) reported
that lighting period did not afect uniformity. According to
our results of uniformity of CSL-NSD may be preferred.
Carcass traits
In terms of carcass traits, it was determined that hot and cold
carcass yields were not infuenced by the treatments inves-
tigated, whilst the weight of the whole breast, as one of the
carcass parts of major interest, was afected by the lighting
period and the entire thigh weight was afected by stocking
density. Some researchers (14, 31) compared group CSL with
group IL (1-h light:3-h dark), observed no statistically sig-
nifcant diference between the groups for heart and gizzard
weights. Tese results, excluding that for the gizzard, are in
agreement with the fndings obtained in the present study.
Onbasilar et al., (26) found that, hot and cold carcass
yields and thigh, breast and tail weights were not afected
by stocking density, as also observed in the present study.
Jayalakshmi et al., (33) reported that while stocking density
had an efect on hot carcass yield (P<0.01), difering from our
results, it had no efect on breast, tail, drumstick and thigh
weights. However, Dozier et al., (7) reported that stocking
density from 30 kg bw/m
2
to 45 kg bw/m
2
had no efect
on cold carcass yield. Tis result is in agreement with that
obtained in this study.
Altanet al., (34) have proposed that the lighting period
does not induce any alteration in hot carcass yield or breast
muscle weight. Tis result is in agreement with ours except
for hot carcass yield. Furthermore, Onbasilar et al., (14) upon
comparing CSL with IL (1-h light:3-h dark) observed no dif-
ference in hot and cold carcass yields or breast, tail and thigh
weights. Excluding those for thigh weight, these fndings
are in support of the results obtained in the present study.
As seen, there numerous diferent fndings on this issue and
Table 3: Mean values and standard error of means of leucocytes of the experimental groups
L SD Heterophile Lymphocyte Eosinophile Monocyte Basophile H/L Ratio
CSL
NSD 39.33±2.42 42.13±2.35 4.93±1.24 2.32±0.65 4.61±0.83 0.92±0.10
HSD 41.12±2.42 39.55±2.35 4.52±1.24 1.62±0.65 5.73±0.83 1.05±0.10
CTL
NSD 22.82±2.42 54.60±2.35 8.42±1.24 2.73±0.65 7.21±0.83 0.43±0.10
HSD 30.70±2.42 51.70±2.35 8.10±1.24 4.54±0.65 6.82±0.83 0.51±0.10
IL
NSD 27.11±2.42 55.32±2.35 7.70±1.24 3.81±0.65 5.11±0.83 0.42±0.10
HSD 33.23±2.42 50.12±2.35 5.82±1.24 4.02±0.65 4.74±0.83 0.63±0.10
NSD 29.71±1.31 50.61±1.35 7.00±0.73 2.93±0.31 5.64±0.42 0.62±0.12
HSD 35.02±1.31 47.13±1.35 6.13±0.73 3.32±0.31 5.72±0.42 0.75±0.12
CSL 40.22
a
±2.43 40.81
b
±2.32 4.70
b
±1.21 1.90
b
±0.60 5.11
b
±0.80 1.01
a
±0.11
CTL 26.71
b
±2.43 53.12
a
±2.32 8.21
a
±1.21 3.62
a
±0.60 7.01
a
±0.80 0.51
b
±0.11
IL 30.11
b
±2.43 52.71
a
±2.32 6.71
ab
±1.21 3.91
a
±0.60 4.91
b
±0.80 0.52
b
±0.11
P<
SD * ** NS NS NS **
L ** ** * ** * **
SDxL NS NS NS NS NS NS
L: Lighting programs; SD: Stocking Density; CSL: Continuous lighting; CTL: Constant lighting; IL: Intermittent lighting; NSD: Normal stocking
density; HSD: High stocking density; NS: No signifcant; SD x L: Interactions between Lighting programs and stocking density; *: P<0.05; **: P<0.01
a, b: Diferences between the means with diferent letters in same columns are important.
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Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 Das, H. 218
therefore these parameters may have to be examined by other
means. We are reporting that there is a signifcant efect on
breast ratio for stocking density and thigh ratio for lighting
period and no efects on hot and cold carcass yield for both
treatments.
Tonic immobility
Te length of the TI period was observed not to have been
afected by either treatments. Researchers, including Ozkan
et al., (23), Stub and Vestegaard (34) compared the CSL
group with the CTL group exposed to 16 h of light and 8
h of dark and determined that no statistically signifcant dif-
ference existed between these groups for the length of the
TI period, thus similar to our results.
However, contradictory to the present study, there are
researches in which CSL has been reported to increase the
length of the TI period (15, 35, 36) and contrary to the fnd-
ings obtained in this study. Previous studies suggest that in-
creased stocking density can increase the length of the TI pe-
riod (15, 37). However, comparable to our results, Skomorucha
et al., (38) stated that stocking density has no efects on TI in
broilers. Tese diferent results may be due to the efects of
diferent practitioners as the TI duration can be afected by
numerous external and internal factors in chickens.
Tibial dyschondroplasia
In the present study, it was determined that no signifcant dif-
ference was observed for the incidence of TD between either
the diferent lighting period groups or the diferent stocking
density groups. In agreement with the fndings of the present
study, Onbasilar et al., (15) reported that the incidence of TD
did not vary with the lighting period.
Gait score
It was ascertained that while the GS was afected by the
lighting period (P<0.01), it was not infuenced by the stock-
ing density. Tere are other studies, which similar to this
research indicate that stocking density has no efect on GS
(39, 40,41). On the other hand, there are other studies that
report GS to worsen with increased stocking density (3, 42,
43). Physiological and anatomical changes that occur in the
organism can be interpreted if multiple factors are taken into
consideration and not only one factor is focused on. Today,
it is well known that gait disorders develop as a result of the
efect of multiple factors (44). In the present study, the most
severe leg disorders having been observed in the group that
was exposed to CSL was attributed to the rapidly increasing
body weights of the animals included in this group. Although
a study is available, which suggest that CSL decreases gait
disorders (45), there are also other studies, which are in
agreement with the present study and indicate that CSL
increases gait disorders (23, 42). Te extremely rapid weight
gain is undesirable causing the metabolic and morphologi-
cal abnormalities. In brief, CSL is not appropriate in terms
of leg health.
Heterophil/lymphocyte ratio
H/L ratios are a reliable marker indicating the presence
of stress in poultry. High value indicates the presence of
more stress than low values. In this study, the H/L ratios of
groups CSL, CTL and IL were determined as 1.0, 0.5 and
0.5, respectively. It was demonstrated that both the stocking
density and lighting schedule had statistically very signif-
cant efects on the H/L ratio (P<0.01). Tere are previous
researches, which similarly to the present study, report that
increased stocking density increases the H/L ratio (15). Tis
study has explicitly demonstrated the efect of the lighting
period on the H/L ratio. While the H/L ratio of groups
CTL and IL were only half of that of group CSL, they did
not difer from each other. Campo et al., (36) compared CSL
with a schedule of 14 h of light and 10 h of dark, and in
agreement with the present study, determined that the H/L
ratio was 1.13 and 0.36, respectively. Tere are further studies
that report the H/L ratio to vary with the length of the light-
ing period (15). In contradiction to the present study, other
research has shown that the H/L ratio does not vary with the
lighting period (23). It was observed that while eosinophil,
monocyte and basophil counts were afected by the lighting
period, they were not afected by the stocking density. H/L
ratios indicated that there was more stress in CSL group.
Te cause of the stress may be that birds rest in the dark in
their natural habitat, however under the circumstances of
continuous light they are currently deprived of this resulting
in a higher metabolic rate.
CONCLUSIONS
1. According to the values of body weight and uniformity
(Coefcients of variation), CSL was superior to other
groups until the end of the trial, while no signifcant dif-
Research Articles
DECEMBER Book.indb 218 04/12/2014 10:57:14
Israel Journal of Veterinary Medicine  Vol. 69 (4)  December 2014 219 Efect of Photoperiods and Stocking Densities on Broilers
ferences were detected between the groups CTL and IL.
When studying cold carcass weight, although the weight
of CSL group was greater than others, this diferences
were not statistically signifcant.
2. Te lighting period and stocking density do not have
efects neither on survival rate nor TI and TD. However,
it was found that gait score of broilers reared in groups
CSL deteriorated.
3. Taking into account H/L ratio, CSL groups were exposed
to more stress than other groups. As in humans (46),
stress may be responsible from eating excessively and as a
result growing fat. Nevertheless, rearing broiler chickens
is an economic issue, getting higher BW with same FCR
and same mortality is indicative of better performance
and more income and even the uniformity was better in
this group. For ethical reasons, requirements of darkness
had to be supplied with the CTL or IL because, broilers
need a dark period for non-stressed life.
4. When examining the efects of stocking density on fat-
tening performance, it was concluded that as stocking
density exceed 36.14 kg/m
2
, performance values dete-
riorated. We highly recommend this value as the upper
limit.
ACKNOWLEDGMENTS
Tis article has been summarized from responsible author’s doc-
toral thesis and the research was supported by the BAP unit of
Ataturk University with Project numbered “BAP 2009/286” and
the briefng papers of this research were presented in the booklet
of International Animal Science Congress of Turkish and Relatives
Communities in 2012.
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