Behavioural responses of white and bronze turkeys (Meleagris gallopavo) to tonic immobility, gait score and open field tests in free-range system

Abstract

This study was carried out to investigate the behavioural responses of white and bronze turkeys to tonic immobility (TI), gait score (GS) and open field (OF) tests in a free-range system. 144 female turkeys (72 white and 72 bronze) were studied for 23 weeks. They were 32 weeks old. The stocking density was 2 birds/m² indoors and 0.66 birds/m² outdoors. Both bird genotypes were fed on a diet containing 16% crude protein and 11.7 ME MJ/kg. The birds were weighed in the 32nd, 35th, 48th and 55th week. The turkeys’ behaviour was determined by TI, GS and OF tests. Behavioural parameters were established for each applied test. Although the mortality rates of white and bronze turkeys during the study were 6% and 3%, respectively, the white turkeys showed better results in the TI and OF tests suggesting that are more native breed than bronze ones. The results indicate that bronze turkeys are more suited for use in free-range systems than white turkeys with respect to GS and the consequent mortality rates in latter ones.

Full text

Behavioural responses of white and bronze turkeys (Meleagris gallopavo) to tonic
immobility, gait score and open field tests in free-range system
Atilla Taskin , Ufuk Karadavut and Huseyin Çayan
Department of Animal Science, Faculty of Agriculture, Ahi Evran University, Kırsehir, Turkey
ABSTRACT
This study was carried out to investigate the behavioural responses of white and bronze turkeys to tonic
immobility (TI), gait score (GS) and open field (OF) tests in a free-range system. 144 female turkeys (72
white and 72 bronze) were studied for 23 weeks. They were 32 weeks old. The stocking density was 2
birds/m
2
indoors and 0.66 birds/m
2
outdoors. Both bird genotypes were fed on a diet containing 16%
crude protein and 11.7 ME MJ/kg. The birds were weighed in the 32nd, 35th, 48th and 55th week. The
turkeys’behaviour was determined by TI, GS and OF tests. Behavioural parameters were established for
each applied test. Although the mortality rates of white and bronze turkeys during the study were 6%
and 3%, respectively, the white turkeys showed better results in the TI and OF tests suggesting that are
more native breed than bronze ones. The results indicate that bronze turkeys are more suited for use
in free-range systems than white turkeys with respect to GS and the consequent mortality rates in
latter ones.
ARTICLE HISTORY
Received 29 December 2015
Accepted 27 June 2018
KEYWORDS
Free-range; genotype; open
field activity; tonic
immobility; Turkey
1. Introduction
The interactions between housing conditions, management
and animals are extremely complex. The impact of environ-
mental conditions on animal welfare has to be considered in
detail (Tuyttens et al. 2008). Numerous factors influence the
ranging behaviour of poultry. Changing the environment of
an animal to support its physical activity can fortify the struc-
tural integrity of its body (Balog et al. 1997). Environmental
changes can contribute to the welfare of animals as well as
their body health. There may be negative effects on animal
health and welfare in intensive production (Maurice et al.
1990). In such environments, animals may be distressed,
which in turn is associated to depressed growth (Schutz et al.
2004), increased injury (Reed et al. 1993), lower production
(De Haas et al. 2013), feather pecking (De Haas et al. 2010)
and a large number of similar negative effects related to pro-
ductivity and welfare. Free-range systems are beneficial for
animals in terms of their health and welfare. In this system,
the outdoor shelter provides a wide free field with sunlight
where animals are able to display their natural behaviour
(Thiele and Pottgüter 2008; Turkoglu and Sarica 2009). Consu-
mers are showing interest in poultry production systems that
are semi-intensive, extensive or free-range. The products from
these systems are more natural and healthy. They are produced
in accordance with the accepted standards of animal welfare.
Their popularity has, therefore, increased year by year (Sarica
and Yamak, 2010).
Various indicators are available to assess the welfare con-
ditions of animals, such as tonic immobility (TI), gait score
(GS) and open field test (OF). Tonic immobility is connected
to disposition and anti-predator behaviour, being a measure
of courage toward predators (Edelaar et al. 2012). The longer
a bird stays still, the higher its level of fear is (Moller and Szép
2011). Tonic immobility (TI) is a connatural reaction of animals
in times of fear, manifesting itself with temporal petrification
or paralysis. Tonic immobility can be observed in a variety of
animals including domestic fowl (Gallup et al. 1972). In a
study by Taskin (2009), adding thyme powder to the basal
diets of broilers lowered the duration of tonic immobility (172
s) to a statistically significant extent (P< .05) when compared
to the control group. It was evidenced that pharmacological
activity of thyme powder had expectorant, antimicrobial, anti-
septic, antioxidative, antivirotic, antihelminthic, sedative, anti-
spasmodic, carminative, diaphoretic and antifungal effects (El-
Hack et al. 2016). In a study conducted on free and intermittent
feeding of turkeys, their tonic immobility duration was found at
327.6 and 427.3 s, respectively (Konca et al. 2004).
Improvements in detection of lameness bring about
enhanced clinical results (Alawneh et al. 2012; Leach et al.
2012). Visual inspection of walking ability offers the advantage
of allowing noninvasive evaluation of large numbers of birds in
a short period of time (Webster et al. 2008). Customary pro-
cedure to assign gait scoring includes the manual scoring of
animal behaviour in the poultry house (Aydin et al. 2010). Dom-
estic fowls have been evaluated mostly by using the gait
scoring system. Birds with a 3- or over gait scores experienced
pain (Kestin et al. 1992; Ferket et al. 2009). Comprehensibility of
the 3-point system currently used in commercial farms in the
United States may encourage observer trustworthiness for
gait scoring in commercial poultry flocks (Webster et al. 2008).
© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distri-
bution, and reproduction in any medium, provided the original work is properly cited.
CONTACT Atilla Taskin ataskin@ahievran.edu.tr Department of Animal Science, Faculty of Agriculture, Ahi Evran University, Kırsehir 40100, Turkey
JOURNAL OF APPLIED ANIMAL RESEARCH
2018, VOL. 46, NO. 1, 1253–1259
https://doi.org/10.1080/09712119.2018.1495642

In a study carried out on turkeys, the proportion of turkeys with
a normal gait was found 56.67% and 64.71% in freely and inter-
mittently fed groups. In turkeys with medium-level difficulties of
walking, the rate was found as 20.0% and 20.59%. The percen-
tage of the free feeding group with symptoms of severe walking
difficulties was 23.33. This ratio was found as 18.75% in the
intermittent feeding group (Konca et al. 2004).
The open-field test was used to investigate the emotional
responsiveness and incentives of laboratory and poultry
animals (Candland and Nagy 1969). Spontaneous locomotor
activity of turkeys was assessed by the open field (OF) test (Bel-
viranli et al. 2012). Activity of animals during the open-field tests
is used to detect behavioural genetic differences between
selected lines or strains (Koolhaas et al. 1999; Wahlsten et al.
2003; Lalonde and Strazielle 2008). Common fear-avoidance is
associated with escaping, jumping and flight behaviours in an
open field test (Melik et al. 2006;O’Brien and Sutherland
2007). Estimates of heritability (h
2
) in open field behaviours
have been observed in several studies and found to range
from 0.08 to 0.49 for overall locomotion and from 0.06 to 0.10
for defecation (Boyer et al. 1970; Faure 1981; Webster and
Hurnik 1989). Ambulation in the open field is also heritable
(Forkman et al. 2007).
As they are more native breeds, bronze turkeys are more
suitable for extensive production methods than white ones
(Camci and Sarica 1991; Cevher and Turkyilmaz 1999; Turkoglu
et al. 2005). For this reason, bronze turkeys are used as stocks in
pasture-based, semi-intensive and extensive turkey farms.
Exogenous factors like feeding, housing and management or
endogenous factors like genetic tendency (Hafez, 1999) have
been propounded to explain the extremely aggressive beha-
viours of domesticated turkeys under commercial rearing con-
ditions (Buchwalder and Huber-Eicher 2004). Fast-growing
strains of turkeys such as B.U.T. BIG 6 are usually housed in
large farms at stocking densities of up to 60 kg/m
2
(FAWC 1995).
There is a huge difference between white and bronze
turkeys in terms of line weight. This affects their behavioural
responses in a free-range system. It may be speculated or
hypothesized that bronze turkeys feel themselves more comfor-
table than white ones since they have got bigger body sizes.
Unlike chickens and quails, turkeys have been under
researched in terms of their welfare (Marchewka et al. 2013).
There is not sufficient research as well to compare the beha-
viours and welfare of white and bronze turkey hens. As
female turkeys are always in large numbers in breeding flocks,
we felt the need to investigate their behavioural responses in
a free-range housing condition. The present study, therefore,
aimed at comparing white and bronze turkey hens in terms
of their responses to TI, GS and OF tests. Comparisons include
the advantage or disadvantage of body weight.
2. Material and methods
2.1. Animals and experimental design
The study was carried out with 144 white (72) and bronze (72)
turkey pullets. They were 32 weeks old and each of them was
designated with a numbered leg ring. It was conducted at the
Poultry Unit of Agricultural Faculty of Ahi Evran University in
Kirsehir province (39° 8′0′′ N, 34° 10′0′′ E) of Turkey. Meteoro-
logical data in experimental unit were collected by using data
loggers (HOBO, Onset, Pocasset, MA). Outdoor climate data
were obtained from the Kirsehir Meteorological Office. Environ-
mental conditions of the free-range system are shown in Table
1. According to the table, average indoor temperature was
between 17.9 °C and 22.5 °C during the 32nd and 55th weeks.
Indoor relative humidity ranged between 57.1 and 69.9%.
In the free-range system, stocking density was 2 birds/m
2
indoors and 0.66 birds/m
2
outdoors. Feed and water were pro-
vided ad libitum indoors. The pens (indoors) were 2.0 × 6.00 m
in size and bedded with fresh wood shavings. Possible inci-
dences of mortality and any other abnormalities were observed
daily. Both animal genotypes were fed on a diet containing 16%
crude protein and 11.7 ME MJ/kg.). The pullets were housed in
pens sized 2 × 6x2 m (height x length x width) indoors and
having free access to the open field area sized 2 × 18 × 2 m
(height x length x width). In open areas, the land is used in its
natural state. In this study, round type plastic feeders and drin-
kers were used. All the birds were weighed on the 32nd, 35th,
48th and 55th weeks. For determining live weight changes of
turkeys and collecting gait and open field test scores, all
animals were used while only 12 animals from each genotype
were used for TI, in order not to distress all animals.
2.2. Tonic immobility test
A tonic immobility (TI) test was conducted in the 32nd and 55th
week according to the modified methods described by Noble
et al. (1996). To measure TI, turkeys were gently taken from
their pens at random and tested individually only once in a sep-
arate room isolated from other environmental events. Within a
few seconds after the bird was caught, it was laid on a flat stand
with fabric lamina. The observer restrained the turkey on its left
side by placing his left hand over its right wing and tenderly
grasped its legs with his right hand. He gradually kept his
hands offthe turkey nearly 15 s later. The duration of its
laying position was counted in seconds with a chronometer.
The turkey was observed from 1-m distance.).
The percentage of one induction (OI, percentage of animals
exhibiting tonic immobility reaction in the first implementation
of the test), vocalizations (V, percentage of sound-making
during the test), defecations (D, percentage of animal feces
during the test), full durations (FD, staying 600 s without stand-
ing up) and tonic immobility duration (TID, standing up willingly
in 600 s without any enforcement) were registered in this study.
These measurements were taken as values of behaviours exhib-
ited by each animal (totally, twelve birds for each genotype). As
the animals exhibited multiple behaviours, each behaviour was
calculated in percentile values.
2.3. Open field test
For open field test, each turkey was singly transferred to an
empty compartment bordering to the compartment in which
they were housed for testing. The open field site consisted of
a square land (3 m x 3 m). The testing site was covered by a
black polycarbonate plate (1.50 m height). Blue plastic strips
were used to form a net of 100 squares (each 0.09 m
2
) on the
1254 A. TASKIN ET AL.

ground. The birds were put in the centre of the site for 10 min
and their behaviours were observed. The behaviours of stand-
ing, sitting, ambulation, vocalization, defecation, and escape
were recorded. Since animals showed multiple behaviours,
each behaviour was calculated in % values. The ethogram is
described in Table 2.
2.4. Gait scores
The scoring system was established by using the system
demonstrated by Ferket et al. (2009) with scores systematically
arranged as following: 0 = no noticeable leg irregularities, 1 =
mild lameness or wobbly leg, 2 = significant lameness and 3 =
lame and lacking ability to move. Gait scores were determined
using a scale ranging from 0 to 3. Gait scoring included the birds
at the age of 32nd and 55th weeks. Their walking abilities were
individually assessed by two estimators while they were
walking within the pen. Each estimator scored the birds freely
and an average score was computed in the sequel.
2.5. Statistical analysis
Bartlett’s and Levene’s tests were used to examine homogen-
eity of variance, and Anderson–Darling and Kolmogorov–
Smirnov tests were used to examine normal distribution.
These tests showed that the assumption of normality was met
for the distribution of live weights. The repeated measures
design was used, therefore, as a parametric statistical test. It
was based on a two-factor experimental design in which one
of the factors involved repeated measurement of levels. The
turkeys were divided into groups on the basis of live weights
and measurement times. Live weights were measured at five
different times.
In what follows, y
ijm
: m refers to the measurement value
obtained from the experimental unit at the i
th
level of factor
A (group) and the j
th
level of factor B (time). Considering the var-
iance elements that could affect this measurement value, the
following linear model was created (Gurbuz et al. 1999).
yijm :
m
+
a
i+
p
m(i)+
b
j+
ab
ij +
bp
jm(i)+1
µ: Overall mean value obtained from turkeys,
α
i
: The effect of the ith level of live weight,
π
m(i)
: The random effect of the mth experimental unit with a live
weight of i,
β
j
: The effect of the jth level of time,
αβ
ij
: The effect of the interaction between live weight and time,
βπ
jm(i)
: The interaction between time and the experimental unit
at the ith level of live weight,
ε
l(ijm)
: The effect of random error.
To identify which group or groups were responsible for the
inter-group differences found, we used Duncan’s multiple com-
parison test (Gomez and Gomez 1984).
To see whether pretest and posttest measurements of inde-
pendent variables, such as tonic immobility, gait score and open
field test results differed from each other, the Mann Whitney U
Test, which is a non-parametric statistical test, was used
(Gamgam and Altunkaynak 2013). All data collected were sub-
jected to Analysis by the Statistical Analysis System Institute
(SAS, 1999).
3. Results and discussion
3.1. Live weight changes
Weekly body weights of the turkey hens are given in Figure 1.As
expected, there was a significant difference between white and
bronze turkeys (P< .05). The variance analysis was carried out for
bronze and white turkeys in accordance with the multiple com-
parison test; the average body weight changed according to the
week (P< .05). In white turkeys, the average live weight was
Table 1. Climate data of indoors and outdoors.
Months
Indoors Outdoors
Temperature (
o
C) Relative humidity (%) Temperature (
o
C) Relative humidity % Areal rains (mm) Max. Wind (m/s) Sunbathe duration (hour)
April 18.1 66.3 13.0 58.1 20.2 19.2 247.7
May 19.6 68.9 16.4 60.8 46.6 20.7 266.7
Jun 19.6 65.4 20.0 53.6 36.0 18.1 294.9
July 22.4 57.1 26.3 38.4 13.0 18.8 362.7
August 22.5 59.4 26.8 39.4 17.0 23.6 339.5
September 19.6 63.1 19.9 51.2 30.4 16.4 261.0
October 17.9 69.9 13.5 67.0 31.6 14.6 218.6
Table 2. Description of the behaviours of turkeys.
Behaviours Description
Standing (ST) Standing, feet or legs, but not belly, on the floor
Sitting (SI) Sitting with breast and belly on the floor
Ambulation (A) Two or more treads in swift progression.
Flying (F) Flapping wings, no contact with floor
Vocalization (V) Production of sounds by birds
Defecation (D) Defecating of the animals during the test
Escape (E) Endeavoring to leap out of the test stage
Figure 1. The changes in body weight (kg) of white and bronze turkeys during 32–
55 weeks (n= 72). Capital letters show significant differences between genotypes
while small letters show significant differences between ages at a significance level
of P< .05.
JOURNAL OF APPLIED ANIMAL RESEARCH 1255

13.85 kg in week 32, and 12.83 kg in week 55. In bronze turkeys,
on the other hand, the initial weight was 6.11 kg, and the average
weight in the final period was 5.65 kg. However, these differ-
ences were not found to be statistically significant within each
genotype. Considering the average rearing period, the average
weights of the white turkeys were 13.17 kg while those of the
bronze turkeys were 5.89 kg. This difference between the geno-
types was found to be statistically significant. Their live weights
also are of significance when they are compared according to the
weeks (P< .05).
3.2. Tonic immobility test
Some physiological changes observed throughout TI suggest
that the autonomic nervous system is powerfully involved in
this process (Alboni et al. 2008). Values for TI (OI, V, IFD and
D) at 32 and 55 weeks of age in turkeys reared in a free-range
system are presented in Figure 2.
In the first measurement (week 32), white turkeys’66.66%
showed OI behaviour (P< .05), 33.33% V behaviour (P< .01),
25% IFD behaviour (P< .05), and 75% D behaviour (P< .01). In
the last measurement (week 55), these birds’58.83% exhibited
OI behaviour (P> .05), 41.66% V behaviour (P< .01), 16.66%
IFD behaviour, and 58.33% D behaviour. The significant
changes (P< .05) were observed in these behaviours. Of the
bronze turkeys, 66.66% exhibited OI behaviour in the first
measurement, 75% V behaviour, 41.66% IFD behaviour, and
91.66% D behaviour. In the last measurement, on the other
hand, 50% of them exhibited OI behaviour, 58.33% V behaviour,
25% IFD behaviour, and 83.33% D behaviour. In bronze turkeys,
also, the significant decreases were observed in these beha-
viours (P< .05). In terms of vocalization behaviour, they
showed less reaction than white turkeys. This could be a geno-
type-related characteristic. In this case, the white turkeys with
an increasing age showed more vocalization behaviour during
the TI test (when incurring the fear condition) compared to
the bronze ones. The significance (P< .05) regarding those
properties (OI, V, IFD and D) when the genotypes are compared
in general and in weeks indicate its relevance to the genotypic
differences.
Initial and final TI durations are shown in Figure 3.A signifi-
cant difference was observed between the white and bronze
turkeys in terms of TI durations. The bronze ones showed a sig-
nificantly shorter duration than the white ones for 55th week.
Considering TI behaviours, significantly lower TID (about 61 s)
(P< .01) was observed in the white turkeys in the 32nd week.
However, TID of bronze turkeys was significantly lower (approxi-
mately 33 s) (P< .05) than the white ones in the 55th week. A
significant decrease in TID of both genotypes indicates that
they were accustomed to free-range system. Significant
decreases (P< .05) in TI in both genotypes from the 32nd to
the 55th week may point to the positive effects of free-range
system on animal welfare.
Bronze turkeys show less fear reactions, which can be inter-
preted as being less affected from free-range conditions. Fear
reactions of turkeys are moderately correlated between days
and weeks (Erasmus and Swanson 2014). Our study is in agree-
ment with these findings. At 32-week old, the bronze turkeys
showed more fear responses than the whites, but the older
bronze turkeys lost this state of fear when compared to the
white ones (P< .01). This might be attributed to the fact that
white turkey is more domesticated than bronze one.
However, it can be speculated that bronze turkeys are accus-
tomed to handling at 55-week old. That was why they
showed less fear. TI is used as a criterion to appraise fear (Villa-
gra et al. 2011). A long duration of TI is mostly considered to be
a sign of high levels of fearfulness (Reese et al. 1984). TI is invo-
luntary and a reflexive state characterized by physical immo-
bility, muscular rigidity, and suppressed vocal behaviour when
confronted with inevitable and fear-inducing situations (Marx
et al. 2008).
3.3. Open field test
Initial and final behavioural elements (ST, S, A, V, E, and D) of the
bronze and white turkeys in the open field test are shown in
Figure 2. Behaviours of female turkeys (mean ± SE) during tonic immobility test
change, (n= 12). OI (One induction); V (Vocalization); IFD (Immobile for full dur-
ation); D (Defecation). Capital letters show significant differences between geno-
types while small letters show significant differences between ages at a
significance level of P< .05.
Figure 3. The average tonic immobility durations (s) of female turkeys (n= 12). t=
5.16 for white, t= 8.91 for bronze in 32–55 weeks, and t=4.5 for between white
and bronze in 32 week, t= 2.83 for between white and bronze in 55 week.
Capital letters show significant differences between genotypes while small
letters show significant differences between ages at a significance level of P< .05.
1256 A. TASKIN ET AL.

Figure 4.ST and SI values were found to be statistically non-
significant in the white turkeys. A, V, E and D were found signifi-
cant (P< .05). As for the bronze ones, A, V and D values were
found nonsignificant while ST, S and E values were found to
be significant (P< .05).
In the open field test, 76.38% of the white turkeys exhibited
ST behaviour in the first test (week 32), 11.11% SI behaviour,
9.72% A behaviour, 27.77% V behaviour, 11.11% E behaviour,
and 77.77% D behaviour. Conversely, in the last test (week
55), 79.41% of them displayed ST behaviour, 14.7% SI behav-
iour, 5.88% A behaviour, 44.11% V behaviour, 7.35% E behav-
iour, and 66.17% D behaviour. The difference between ST and
SI behaviours was not statistically significant; however, there
was a significant increase in V behaviour over time (P< .01)
while the significant decrease was observed (P< .05) in the
other behaviours in open field test. In the first measurement,
76.38% of the bronze turkeys exhibited ST behaviour, with
23.61% SE behaviour, 13.88% A behaviour, 62.5% V behaviour,
19.44% E behaviour, and 69.44% D behaviour. In the last
measurement, however, 85.71% of them exhibited ST behav-
iour, 14.28% SI behaviour, 12.85% A behaviour, 57.14% V behav-
iour, 34.28% E behaviour, and 68,57% D behaviour. As for the
bronze turkeys, differences between ST, SI and E behaviours
were found to be both large and significant (P< .01);
nevertheless, no significant differences were observed in
terms of A, V and D behaviours (P> .05). The open field test
scores of turkeys differed in terms of both weeks and geno-
types. Both genotypes scored differently in the last week in pro-
portion to the first week. As it can be seen in the groupings of
turkeys according to the multiple comparison tests (Figure 4),
those differences are statistically significant (P< .05), which
shows that the reactions of both genotypes changed over
time. Positive changes are important in terms of rearing. The
most striking aspect here was the noise the turkeys made
when they got outdoors. The bronze genotypes made more
noise than the white ones did, possibly due to the fact that
the former ones genetically have a more fierce temperament.
These differences between white and bronze turkeys are
thought to stem from the relevant genotypes. In a study on
enriched and non-enriched pens, there was no treatment
effect on latency for birds to move out of the starting square
in which they were placed, and no effect on the frequency of
escape attempts or number of defecations (Hartcher et al.
2015).
3.4. Gait scores
Gait scores (%) of the bronze and white turkeys at the begin-
ning and the end of the study (GS0, GS1, GS2 and GS3) are
shown in Figure 5.Those scores (%) were significant (P< .05)
in the 32nd and 55th weeks.
In the first measurement (week 32), 62.5% of the white
turkeys displayed GS0, with 34.94% GS1, 5.56% GS2, and 0%
GS3. In the last measurement (week 55), however, 55.88% of
them displayed GS0, with 19.11% GS1, 13.24% GS2, and
11.77% GS3. Differences between behaviours were found to
be large and significant (P< .01; P< .05 for GS0). In the bronze
genotypes, 74.99% displayed GS0 in the first measurement,
20% displayed GS1, 5.71% displayed GS2, and 0% displayed
GS3. In the last measurement, on the other hand, 85.71% dis-
played GS0, 11.43% displayed GS1, 1.43% displayed GS2, and
1.34% displayed GS3. Differences between the gait scores of
bronze turkeys were found to be large and significant (P< .01;
P< .05 for GS0). This indicates that the free-range system has
eventually generated a positive impact on the gaits of bronze
turkeys. In terms of gait scoring, the turkeys differed signifi-
cantly in GS0, GS1, GS2, GS3 according to their genotypes.
The fact that GS0 was higher among the bronze genotypes
show that they did not have walking difficulties. GS1, GS2 and
GS3 were also statistically lower among them, which indicates
that the bronze turkeys can reap the benefits of free-range
systems more actively than the white ones can. It needs to be
further elaborated as this property also makes it possible to
use feeding and housing in a more efficient way.
Exercises in free-range systems increase the metabolic
activity and circulation, which may contribute to reducing the
animal’s stress (Kjaer 2004). It has been seen that there are
fewer incidences of lameness in free-range chickens (Kestin
et al. 1992). The increasing age negatively affected the gait of
white turkeys, on the other hand. This effect stems from the
high body weights depending on the genotype. Gait scores
of the bronze turkeys improved in general. Examination of
the heavier B.U.T. T9 and Big 6 strains revealed incidences of
Figure 4. Open field scores (%) of female turkey (n= 72). ST (Standing); SI (Sitting);
A (Ambulation); V (Vocalization); E (Escape); D (Defecation). Capital letters show
significant differences between genotypes while small letters show significant
differences between ages at a significance level of P< .05.
Figure 5. Gait scores (%) of female turkey (n= 72). Capital letters show significant
differences between genotypes while small letters show significant differences
between ages at a significance level of P< .05.
JOURNAL OF APPLIED ANIMAL RESEARCH 1257

tibial dyschondroplasia with 88.2% and 90.5%, respectively
(Reinmann 1999). The white turkeys were heavier than the
bronze ones. At sexual development (27–34 weeks), all female
turkeys of a heavy breeding line exhibit cartilage lesions
(Hocking and Lynch 1991). This situation (genetic predisposi-
tion) can account for the worse gait scores of the white
turkeys as well. Keeping commercial breeds under free-range
conditions reduced, but did not eliminate lameness (Kestin
et al. 1992). In some cases, the frequency of leg disorders can
be high and are connected to elevated rates of mortality
(Sanotra et al. 2002). In the present study, mortality rates were
found higher among the white turkeys. The white turkeys
showed a 6-percent mortality while that of the bronze ones
was 3%. The results may be related to these rates.
4. Conclusions
The bronze female turkeys showed lower mortality compared
to the white turkeys. The bronze ones responded with more
natural behaviours to TI and OF tests, albeit not to GS. The
results suggest that bronze turkeys are more comfortable
than white ones in free-range systems. Considering their behav-
ioural responses to ambient conditions, bronze turkeys may be
more suitable than white turkeys for rearing in free-range
systems.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This study was supported by the Scientific Research Projects Coordinator-
ship of Ahi Evran University in Turkey with AEU-PYO-ZRT.4001.12.016
project number.
ORCID
Atilla Taskin http://orcid.org/0000-0001-5897-2062
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