Received: 4 October 2019
Accepted for publication: 20 April 2020
Slov Vet Res 2020: 57 (3): 133–43
DOI 10.26873/SVR-971-2020
UDC  636.5.083:304.35:636.083.312/.314
Introduction
The welfare of laying hens in modern intensive 
production units has been recognized as an 
important aspect of poultry management. Several 
factors can influence the welfare of laying hens, 
such as diseases, skeletal health, behavior, 
stress, nutrition, genetics, and management. 
Housing systems may play a critical role in the 
welfare of laying hens, and various systems have 
been implemented throughout the world. In the 
European Union, conventional battery cages were 
the dominant housing system for laying hens until 
Original Research Article
WELFARE ASSESSMENT OF COMMERCIAL LAYERS IN 
SLOVENIA
Olga Zorman Rojs1*, Alenka Dovč1, Hristo Hristov2, Matjaž Červek3, Brigita Slavec1, Uroš Krapež1, Zoran Žlabravec1, Jožko 
Račnik1, Manja Zupan4
1Institute for Poultry, Birds, Small Mammals, and Reptiles, Veterinary Faculty, University of Ljubljana, Gerbičeva 60, 2Nutrition Institute, Tržaška 
cesta 40, 3Emona, Razvojni center za prehrano d.o.o., Kavčičeva ulica 72, 1000 Ljubljana, 4Department of Animal Science, Biotechnical 
Faculty, University of Ljubljana, Groblje 3, 1230 Domžale, Slovenia
*Corresponding author, E-mail: olga.zorman-rojs@vf.uni-lj.si
Abstract: Here we present the first welfare assessment of commercial layers conducted in Slovenia. Hens were assessed in four 
systems at the beginning of the laying period at 22 to 24 weeks and at 50 to 55 weeks of age. These systems were an enriched 
battery cage system, an aviary, and a litter system with or without outdoor access. Clinical inspections of flocks were performed, 
and animal-based welfare indicators were scored (e.g., keel bone damage, feather condition, foot pad lesions, beak deformi-
ties, and comb and skin wounds). Hens’ fear level was scored using the novel object test and avoidance distance test. Among 
resource-based measures, selected micro-climate parameters were measured.
The results showed no obvious clinical signs related to infectious diseases and suggest that the selected climate conditions were 
satisfying in all systems. Among animal-based welfare indicators, keel bone damage was shown to be the most serious problem 
connected with hens’ age and housing systems (p < 0.05). Enriched cages and aviary system were associated with significantly 
more keel deformities compared to the litter systems (p < 0.05). In addition, the least prevalence of foot pad dermatitis together 
with better feather condition was observed in the litter systems. In the family-owned aviary facility, hens were found to be the most 
motivated to approach a novel object or a human, and as such were recognized as the least fearful birds, with better human–ani-
mal interaction compared to other intensive housing systems.
Key words: laying hens; welfare; health; housing system
their official ban on January 1st, 2012 (1). The ban 
on traditional cages was mainly adopted because 
of welfare concerns due to a lack of adequate 
space for performance of natural behaviors and 
an increased risk of bone deformities. According 
to an official report by the European Commission 
(2), enriched cages, aviaries, and floor housing 
are the most common housing systems used for 
commercial laying hens in the EU. In Slovenia, 
approximately 1.9 million hens are kept for egg 
production per year (3). Most hens (more than 
40%) are kept in enriched cages, around 39% are 
kept in litter systems, including aviaries, and a 
smaller proportion of hens (16.3%) are in facilities 
under free-range conditions (2, 4).
134 O. Zorman Rojs, A. Dovč, H. Hristov, M. Červek, B. Slavec, U. Krapež, Z. Žlabravec, J. Račnik, M. Zupan
Enriched cages were introduced to allow 
birds more movement; they have extra facilities 
such as a nest box and at least 15 cm of perch 
per hen. Floor housing and aviaries are non-cage 
systems. These systems have the same facilities as 
enrichment cages (i.e., perches and nest boxes), 
but the group size and litter area are considerably 
larger. In a floor system, all hens are in a facility 
on one level, whereas in aviaries they have access 
to at least two levels and as such aviary systems 
allow higher stocking densities. The systems 
encourage birds to carry out natural behaviors 
such as nesting and perching, and they provide 
access to floor litter. The aviary and floor housing 
systems have the distinct disadvantage that the 
birds are exposed to litter and excreta, creating 
potential health and food safety concerns.
Finding a reliable method to assess bird 
welfare has been slow, and it was only in 2009 
that the first protocol was published, presenting 
a gold standard. The Welfare Quality® assessment 
protocol for poultry (5) is based on the concept 
that welfare is multidimensional, addressing 
both physical and mental health (6). It focuses 
on animal-based measures (e.g., injuries and 
behavior) as well as on resource-based measures 
(i.e., design or management criteria), making 
possible welfare comparisons across farms and 
housing systems.
Until now no assessment of commercial 
layers has been conducted focusing on welfare 
indicators in Slovenia. This study included hens 
from four systems: an enriched battery cage 
system, an aviary, and a litter system with or 
without outdoor access. The selected animal-based 
welfare indicators were keel bone damage, feather 
condition, foot pad lesions, beak deformities, and 
comb and skin wounds. Hens’ behavior was scored 
using the novel object and avoidance distance test. 
To investigate the possible development of selected 
welfare indicators connected with age, assessments 
were performed at two time points: at the beginning 
of the laying period at 22 to 24 weeks, and at 50 
to 55 weeks of age. In addition, selected climate 
parameters were measured at each assessment.
Materials and methods
Animals and housing
Four commercial flocks of Lohmann Brown 
hens were assessed in the study. The birds were 
beak trimmed in the hatchery and reared in a floor 
system or in an aviary system. At approximately 16 
weeks of age the pullets were moved to commercial 
egg facilities. Pullets reared in a floor housing 
system were housed in either the enriched cage 
system (ECS) or the litter system with (LOS) or 
without (LS) outdoor access, whereas pullets 
reared in the aviary system were moved to the 
facility with the aviary system (AS). The flocks had a 
similar vaccination program; they were vaccinated 
against Marek disease, infectious bronchitis virus, 
infectious bursal disease virus, Newcastle disease 
virus, and Salmonella Enteritidis. The vaccinations 
were performed before transfer to commercial egg 
facilities. The flocks had the same feed supplier 
during the rearing and the laying period and were 
managed according to the same standard practices, 
but the owners of the facilities and the birds’ keepers 
were different. The ECS was populated by 37,860 
hens. The facility had four double-sided rows with 
three tiers, and each cage housed 20 hens. The 
cages were furnished with perches, nest boxes, a 
scratching pad, and a water line (Big Dutchman). 
The AS (Big Dutchman) was populated with 13,800 
laying hens. The hens had perches, a forage area, 
nest space, and a litter area accessible to the hens 
to perform foraging and dust-bathing behaviors. 
The LS was populated by 3,820 hens. The facility 
was equipped with a nipple water system, a feeder 
line, an automatic nest system, and wood shavings 
(Roxell). The LOS was populated by 4,420 hens. 
The hens had the opportunity to go outside for 4 
to 6 hours a day. The equipment of the facility was 
the same in both litter systems.
Observations
Each flock was visited two separate times 
during the laying period, at 22 to 24 weeks and 50 
to 55 weeks of age. The visits took place between 
November 2016 and October 2017 and were 
carried out by the same observers. Information 
on farm and flock management (e.g., hybrid, flock 
size, and age when birds were introduced to the 
farm) as well as cumulative flock mortality (e.g., 
percentage of dead or culled hens) was collected 
from the farm records. At each visit, the following 
climate parameters were checked: temperature, 
ammonia (NH3), relative humidity, and air velocity. 
Each parameter was measured at three locations 
within the facility. Temperature, relative humidity, 
and airflow were measured with a Testo 543 
135Welfare assessment of commercial layers in Slovenia
instrument (Testo SE & Co. KGaA, Germany), and 
the level of ammonia was measured using Dräger 
Multiwarn II (Dräger, UK). All measurements 
were performed at animal level, and the average 
values of three measurements of each parameter 
were calculated. General clinical flock observation 
was performed by walking throughout the facility, 
and each flock was checked for the presence of 
clinical signs of respiratory disorders, diarrhea, 
enlarged crops, and leg problems. Clinical 
indicators of health problems were scored on a 
three-point scale (0 = none, 1 = fewer than three 
birds, 2 = three or more birds). Infestation with 
Dermanyssus gallinae was checked by looking for 
the presence of the parasite on hens and on the 
surface of equipment and eggs.
The following parameters were additionally 
scored for presence and severity on an individual 
hen: foot abnormalities, feather condition, comb 
wound, skin lesions, beak abnormalities, and 
keel bone damage. A description of the physical 
condition measurements and severity scoring 
system is presented in Table 1. Foot abnormalities 
were evaluated by examining both legs. Overall 
feather condition was evaluated by examination 
of the head, neck, back, and belly. For the 
assessment of skin lesions, the entire body of each 
hen was checked, including the region around the 
vent. Keel damage was determined by palpation 
to detect abnormal curvatures of the keel or bony 
callouses indicative of healed fractures. At each 
visit, 100 hens were examined in the AS and ECS, 
and 50 hens in the LOS and LS. Birds were caught 
individually from different locations in the facility 
and released after scoring.
Hens’ behavior was scored using the novel 
object test (NOT) and the avoidance distance 
test (ADT) following the procedure described in 
the Welfare Quality® protocol. Both tests were 
performed after the clinical assessment of the 
flock to accustom the birds to human presence. 
The novel object (NO) used was a 45-cm stick with 
multicolored bands. In both litter facility systems 
and in the AS, the NO was placed in the litter area, 
and in the ECS the NO was placed in the feeder. 
At each visit, four locations in the facility were 
scored. The observer started to record the number 
of hens within one hen’s distance of the NO (about 
35 cm) every 10 s for a total period of 2 min. The 
average outcome of all four NOTs was calculated 
for each flock. The ADT was performed in 21 birds 
from different locations within each facility. In the 
AS, LS, and LOS the observer slowly approached 
the bird sitting on the edge of the slatted area. 
Condition Score description
Foot pad lesions 0 = no lesion present
1 = proliferation of epithelium
2 = foot swelling dorsally visible
Feather condition 0 = completely or almost completely feathered, only single feathers damaged
1 = damaged feathers (worn, deformed) or one or more featherless areas < 5 cm 
in diameter at largest extent
2 = at least one featherless area ≥ 5 cm in diameter at largest extent
Comb wound 0 = no wounds present
1 = < 3 fresh wounds present
2 = > 3 fresh wounds present
Skin lesions 0 = no lesions present
1 = < 3 lesions present
2 = > 3 fresh wounds present
Beak abnormalities 0 = no trimming, no abnormalities
1 = moderate to light trimming with moderate to no abnormalities
2 = severe trimming with clear abnormalities
Keel bone damage 0 = no deformation
1 = minor S-shape deviation
2 = severe keel deformities
Table 1: Description of physical condition measurements and severity scoring system
136 O. Zorman Rojs, A. Dovč, H. Hristov, M. Červek, B. Slavec, U. Krapež, Z. Žlabravec, J. Račnik, M. Zupan
When the hen turned away, the distance from the 
hand of the assessor to the bird was measured. 
In the cage house the observer walked down the 
corridor and approached a hen with her head out 
of the cage. As soon as the hen pulled her head 
into the cage, the distance between the observer 
and the front of the cage was estimated. The mean 
avoiding distance was calculated for each flock.
Statistical analysis
The Statistical Package for the Social Sciences 
was used for the statistical analyses. Variables of 
individual welfare measurements (beak and foot 
abnormalities, comb wounds and skin lesions, 
feather condition, and keel deformities) were 
analyzed using the non-parametric Kruskal–
Wallis test for comparison at each visit, followed 
by pair comparisons with the Wilcox Signed Rank 
test when significant (p < 0.05). The relationship 
between age and animal-based welfare indicators, 
and the association between housing system and 
animal-based welfare indicators were tested with 
Fisher’s exact test (p < 0.05).
Results
General observation of health and welfare
The flocks examined were healthy at both visits. 
Signs of enteritis, eye abnormalities, respiratory 
disorders, leg problems, or pendulous crop were 
observed in fewer than three birds per flock at each 
visit. At the first visit no external parasites were 
detected, and good feather condition was noted in 
all the systems. At the second visit the AS hens 
showed greater feather loss compared to the other 
hens, but no signs of vent pecking were observed 
in any of the flocks. In the ECS birds, infestation 
with Dermanyssus gallinae was confirmed.
Cumulative flock mortality (percentage of dead 
or culled hens) is presented in Figure 1. At the 
first visit the lowest mortality was recorded in 
the ECS (0.21%), followed by the AS (0.56%) and 
both litter systems (0.9%). At the second visit the 
mortality ranged from 2.1% in the AS to 4.79% in 
the LS (Figure 1).
The selected climate conditions recorded at 
each visit are presented in Table 2. The average 
RH values within facilities ranged from 55.3 to 
74.2%. The level of NH3 exceeded the anticipated 
level of 20 ppm only at the first visit in the LOS 
and LS.
Specific observations
Beak abnormalities
Although the birds were beak trimmed at 
the hatchery, at the first visit four hens from 
the ECS had intact beaks. Significantly more 
abnormalities were observed in the LOS hens (p 
< 0.05) compared to the hens from other systems. 
At the second visit, 12% of the birds examined 
from the AS and ECS were scored 2, whereas all 
hens from the LOS and LS were scored 1 (p < 0.05) 
(Figure 2).
Comb wounds
Comb wounds were rare. At the first observation 
no comb wounds were observed in the ECS, 
AV, and LS, whereas in the LOS 18% of hens 
were scored 1. Significantly more wounds were 
confirmed in the LOS and ECS compared to the 
AS and LOS (p < 0.05). At an older age, no comb 
abnormalities were observed in the LOS, but they 
were noticed in individual birds from the other 
three systems. The highest score was obtained in 
the AS, but it did not significantly differ from the 
ECS and LS (Figure 3).
Skin lesions
At both visits, skin lesions were rarely detected, 
and no hen was scored 2. At the first visit, 1 to 
4% of hens with a score of 1 were recorded in 
the ECS, LOS, and AS. Even better results were 
obtained at the second visit; mild skin lesions were 
detected in 2% of the AV and EC hens, but not 
in litter systems (data not shown). No significant 
differences were found between housing systems 
at any observation (p > 0.05).
Foot abnormalities
At the beginning of the laying period, no foot 
pad lesions were seen in the LOS and LS, whereas 
significantly more foot abnormalities (p < 0.05) 
were recorded in the ECS and AS; 6% of the ECS 
hens and 10% of the AS hens were scored 1, and 
one hen (2%) from the AS had severe inflammation 
(score 2). At the second visit, no score of 2 was 
recorded, although 16% of the ECS hens and 12% 
of the LOS hens had hyperkeratosis on one or 
both feet. In the AS or LS, only a few abnormalities 
were detected (Figure 4).
137Welfare assessment of commercial layers in Slovenia
Parameter
Litter system, no
outdoor access
Litter system,
outdoor access
Enriched
cages
Aviary
system
V1 V2 V1 V2 V1 V2 V1 V2
Age (weeks) 22–24 50–55 22–24 50–55 22–24 50–55 22–24 50–55
Inside temp. (°C) 13.6 20.1 13.6 19.3 20.3 13.5 20.5 18.9
NH3 (ppm) 24 4.3 24 4.3 nd nd 4 3
Rel. humidity (%) 66.8 74.2 66.8 74.2 69.9 68.1 58.4 55.3
Airflow (m/s) 0.23 0.126 0.23 0.126 0.21 0.43 0.19 0.22
Figure 1: Cumulative mortality and culling per age and housing system
Table 2: Average values of selected climate parameters at both visits (V1, V2)
Figure 2: Percentage of hens with beak abnormalities 
at 22 to 24 and 50 to 55 weeks of age housed in a lit-
ter system with outdoor access (LOS), enriched cages 
(ECS), a litter system (LS), and an aviary system (AS). 
Beaks were scored 0 when no abnormalities were ob-
served, 1 if abnormalities were mild, and 2 if severe. 
Bars with different letters (lower-case letters for the first 
assessment, upper-case letters for the second assess-
ment) indicate significant differences (p < 0.05) between 
housing systems
Figure 3: Percentage of hens with comb wounds at 22 to 
24 and 50 to 55 weeks of age housed in a litter system 
with outdoor access (LOS), enriched cages (ECS), a litter 
system (LS), and an aviary system (AS). Combs were 
scored 0 when no wounds were observed, 1 if fewer 
than three fresh wounds were present, and 2 if three 
or more fresh wounds were present. Bars with different 
letters (lower-case letters = first assessment, upper-
case letters = second assessment) indicate significant 
differences (p < 0.05) between housing systems
138 O. Zorman Rojs, A. Dovč, H. Hristov, M. Červek, B. Slavec, U. Krapež, Z. Žlabravec, J. Račnik, M. Zupan
Figure 6: Percentage of hens with feather damage at 22 
to 24 and 50 to 55 weeks of age housed in a litter sys-
tem with outdoor access (LOS), enriched cages (ECS), 
a litter system (LS), and an aviary system (AS). Feather 
condition was scored 0 when a hen was completely or 
almost completely feathered, 1 if damaged feathers or 
one or more featherless areas < 5 cm in diameter were 
present, and 2 if there was at least one featherless area 
≥ 5 cm in diameter present. Bars with different letters 
(lower-case letters = first assessment, upper-case let-
ters = second assessment) indicate significant differ-
ences (p < 0.05) between housing systems.
Figure 4: Percentage of hens with foot abnormalities at 
22 to 24 and 50 to 55 weeks of age housed in a litter sys-
tem with outdoor access (LOS), enriched cages (ECS), 
a litter system (LS), and an aviary system (AS). Foot 
lesions were scored 0 when no lesions were present, 1 
if proliferation of epithelium was seen, and 2 if there 
was swelling on the dorsal surface of the foot. Bars with 
different letters (lower-case letters = first assessment, 
upper-case letters = second assessment) indicate sig-
nificant differences (p < 0.05) between housing systems
Figure 5: Percentage of hens with keel bone damage at 
22 to 24 and 50 to 55 weeks of age housed in a litter sys-
tem with outdoor access (LOS), enriched cages (ECS), a 
litter system (LS), and an aviary (AS). Keel bone damage 
was scored 0 when there was no deformation, 1 if minor 
S-shaped deviation was observed, and 2 if there were 
severe keel deformities. Bars with different letters (low-
er-case letters = first assessment, upper-case letters = 
second assessment) indicate significant differences (p < 
0.05) between housing systems.
Keel bone deformities
Keel bone damage was observed in 8% of the 
ECS hens at the first visit. Although one severe 
deformity was scored in the AS, there was no 
significant difference between the AS and both 
litter systems at this age (p > 0.05). At the second 
visit, the highest score of keel bone deviations 
was confirmed in the AS, followed by the ECS, but 
the difference was not significant (p > 0.05). In 
the litter system with or without outdoor access, 
significantly (p < 0.05) fewer hens with keel bone 
damage were identified (Figure 5).
Feather condition
A difference in feather condition between hens 
in different systems was found during the second 
visit (p < 0.05) but not the first (p > 0.05). The hens 
in the ECS had the highest score, followed by the 
AS and LS. The lowest score was recorded in the 
LOS, where 18% of hens scored 1 (Figure 6).
The similarity of proportions between housing-
system and animal-based welfare indicators is 
presented in Table 3. The results show that except 
for comb wounds all other indicators differentiate 
between housing systems.
The relationship between animal-based welfare 
indicators and hens’ age was tested using Fisher’s 
exact test (Table 4).
139Welfare assessment of commercial layers in Slovenia
Parameter Score
Housing system Fisher’s exact 
test
p-value
LOS
(n = 100)
ECS
(n = 200)
LS
(n = 100)
AS
(n = 200)
Feather condition 0 91 102 73 128 < 1e-07*
1 9 46 21 36
2 0 53 6 36
Keel bone damage 0 98 144 97 132 < 1e-07*
1 0 6 3 18
2 2 50 0 50
Comb wounds 0 91 190 98 185 0.2115
1 9 8 2 12
2 0 2 0 3
Skin lesions 0 98 197 100 194 0.0008*
1 2 3 0 6
2 0 0 0 0
Foot pad lesions 0 94 178 98 187 0.03492*
1 0 22 2 12
2 0 0 0 1
Beak deformities 0 0 4 0 0 0.00019*
1 92 173 100 188
2 8 23 0 12
Table 3: Occurrence of clinical welfare indicators in hens from different housing systems
Parameter Score Observation period Fisher’s exact test
p-value22–24 w (n = 300) 50–55 w (n = 300)
Feather condition 0
1
2
298
2
0
95
110
95
< 2.2e-16*
Keel bone damage 0
1
2
291
6
3
180
21
99
< 2.2e-16*
Foot pad lesions 0
1
2
283
16
1
274
26
0
0.149
Skin wounds 0
1
2
283
7
0
296
4
0
0.566
Comb wounds 0
1
2
285
13
2
279
13
3
0.601
Beak deformities 0
1
2
4
277
19
0
276
24
0.1147
Table 4: Occurrence and scores of clinical welfare indicators at two ages
*An asterisk indicates significant differences in the occurrence of clinical welfare indicators among housing systems at the 0.05 level using Fish-
er’s exact test
*An asterisk indicates significant differences in the occurrence of clinical welfare indicators at different ages at the 0.05 level using Fisher’s exact 
test
140 O. Zorman Rojs, A. Dovč, H. Hristov, M. Červek, B. Slavec, U. Krapež, Z. Žlabravec, J. Račnik, M. Zupan
The results showed that feather condition and 
keel bone damage were associated with hens’ age.
Hens’ behavior
Hens’ behavior was scored on the NOT and 
the ADT, and the results are presented in Table 
5. At both visits the highest average count of 
birds close to the NO was in the AS. In the ADT, 
a larger average distance indicative of increased 
fearfulness of humans was recorded in the LS 
hens, followed by the LOS and ECS hens. The 
overall results show that the AS hens expressed 
less general fearfulness as well as a better human–
animal relationship compared to hens kept in the 
other three systems.
Discussion
This study evaluated some aspects of welfare 
in the four most common rearing systems for 
layers used in Slovenia; enrichment battery 
cages, aviaries, and litter systems with or without 
outdoor access. To investigate the possible 
development of selected welfare indicators with 
age, assessments were performed at two time 
points; at the beginning of the laying period at 22–
24 weeks and at 50–55 weeks of age. The results 
suggest that the intensive housing conditions 
for laying hens in Slovenia are satisfactory from 
the health and welfare point of view. Finding a 
better psychological profile for birds in the aviary 
system on a small family farm may emphasize the 
importance of human contact for birds’ welfare.
Records of the clinical condition of farm 
animals such as mortality or diseases are among 
the earliest welfare indicators used (7). The four 
flocks included in our study were in good health, 
and no obvious clinical signs related to infection 
diseases were seen. In the ECS hens, infestation 
with Dermanyssus gallinae was confirmed at the 
second assessment. The flock was treated with 
Byemite® and no obvious effect on mortality was 
noted. The mortality from placement to 50 to 55 
weeks of age did not exceed the expected rate for 
each farm. The lowest cumulative mortality was 
recorded in the AS hens (2.1%), followed by the 
ECS (3.7%) and both litter systems (4.2 and 4.8%). 
Mortality rates in layer flocks have previously 
been reported between 2.9 to 15.5% in enriched 
cages (8), and 5 to 20% for non-cage systems (6). 
Weeks (9) conducted a quantitative analysis on 
the mortality of 3,851 commercial flocks recorded 
across Europe. The results showed that mortality 
rates in layer flocks tend to be higher in non-cage 
systems compared to enriched cage systems. In 
addition, a review by Nicol (10) noted that mortality 
in free-range and aviary systems is highly variable.
Air quality in the housing systems could have 
an important effect on health. High concentrations 
of ammonia can have adverse health effects and, 
when very high, can even influence production 
performance. The most profound effects 
seen are lesions in the respiratory tract and 
keratoconjunctivitis (11). According to European 
regulations (12, 13), occupational exposure limit 
values are set at 20 ppm. Slightly exceeded levels 
of ammonia were recorded at the first assessment 
in the facilities with litter systems. It is known 
that concentrations of ammonia could be high 
in floor housing systems in which manure is not 
regularly removed. Both observations were made 
in the winter, and the levels of ammonia might 
be due to reduction of ventilation to maintain a 
suitable indoor temperature. Overall, it can be 
concluded that the indoor climate was satisfactory 
in all systems.
System
Novel object test1  
(average hens close to the NO)
Avoidance distance test2 (mean avoidance 
distance in cm and range)
22–24 weeks 50–55 weeks 22–24 weeks 50–55 weeks
LS 0.68 0.75 33.10 (10–100) 30.70 (10–120)
LOS 0.68 0.74 32.99 (10–100) 28.09 (10–100)
ECS 0.21 0.39 19.20 (10–30) 20.90 (15–50)
AV 2.28 3.56 16.70 (10–50) 17.15 (10–60)
Table 5: Average results of the NOT and ADT obtained at different observation periods in four different housing 
systems
1 Average of observations performed at four locations
2 Average of 21 hens scored at three locations
141Welfare assessment of commercial layers in Slovenia
This study showed that the condition of the 
keel bone and feathers in layers housed in various 
housing systems in Slovenian commercial farms 
were affected by hens’ age, and that the ECS 
and AS were associated with significantly more 
keel deformities and poorer feather condition 
compared to the litter systems.
The keel bone is known to be a site of frequent 
fractures during the production life of laying 
hens, with incidence rates ranging from 5% to 
over 85%, and it is known that hens in all types of 
housing systems are susceptible to keel fractures 
(14). Several studies have also shown that the 
prevalence of keel bone fractures increases 
throughout the laying period (15–18). In our study, 
keel bone deformities were already detected at the 
beginning of the laying period in the ECS and AS 
hens. These early deformities could be caused 
by the keels being damaged during handling or 
transport from rearing to the production facility. 
Although keel bone damage was observed at the 
second assessment in all systems compared, the 
differences between systems were significant. 
Moderate to severe deformities were found in 67% 
of the AS hens and 48% of the ECS hens, whereas 
in the LOS and LS hens only 4 to 6% had keel 
bone deformities. Bone fragility in laying hens is 
related to high egg production, musculoskeletal 
health, and restricted movements (19). However, 
bone fractures are a risk when hens fall during 
flight on objects such as perches, feeders, and 
drinkers within the facility, which might be the 
main reason for the high occurrence of keel bone 
damage found in the AS. On the other hand, hens 
housed in the ECS are less active than in non-
cage systems, which increases the susceptibility 
to weak bones and osteoporosis (17).
Previous studies comparing feather damage in 
different housing systems have reported diverging 
results; some studies showed a lower prevalence in 
cage system compared to non-cage system (20, 21). 
On the contrary, other studies showed a higher 
prevalence in hens housed in enrichment cages 
compared to hens housed in litter systems (22). The 
poor feather condition found in almost all the ECS 
hens in our study might also be linked to the red 
mite infestation that was present in the facility. The 
presence of mites in a production house induces a 
high level of stress from pain and skin irritation 
associated with repeated mite bites. In addition, 
mite infestations induce increased self-grooming 
and aggressive feather-pecking behavior (23).
Foot lesions are present in laying hens housed 
in all systems, although some studies have 
indicated that layers in enriched cages have 
better foot health than those in other production 
systems (19). Wet litter, a high level of ammonia, 
and poorly designed and maintained perches have 
been associated with foot injuries in litter systems 
(19, 24, 25). In cage systems, hens are kept on 
wire mesh, which may cause superficial epithelial 
lesions and hyperkeratosis (26, 27). In this study 
the occurrence of foot injuries was low and almost 
no severe inflammation (i.e., bumblefoot) was seen 
in any system. At both observations, hens kept 
in systems using wire mesh as flooring material 
(the AS and ECS at the first assessment and the 
ES at the second assessment) had more foot pad 
dermatitis compared to both litter systems. The 
prevalence of foot pad lesions has previously been 
found to be higher in younger hens compared 
to older ones (17). In our study no association 
between hens’ age and foot lesions was confirmed.
The assessment of mental wellbeing of hens 
was performed by using two tests included in 
the Welfare Quality® protocol. The NOT measures 
the conflicting motivation to approach and avoid 
a novel object (28). The time spent near a novel 
object can therefore be used to quantify an 
animal’s fearfulness. The results of our study 
showed that the AS hens were the most motivated 
to approach a NO at both observation periods. The 
lowest numbers were obtained in the ECS hens, 
possibly because of the lack of free space and 
because the object was not visible for all hens. In 
the ADT, which reflects animals’ fear of humans 
(29), hens in both litter systems showed more fear 
compared to the AS hens. However, it should be 
mentioned that the results of both tests in the 
ECS might be difficult to compare with non-cage 
systems because there is a wire door between 
the observer and hens. It was shown that hens 
in large commercial facilities tend to be fearful of 
human contact (30) and that fearfulness can be 
reduced through appropriate familiarization (31). 
Three flocks (ECS, LOS, and LS) in our study were 
housed on large commercial farms, whereas the 
hens from the AS were kept on a small family 
farm. At both assessments these hens expressed 
less general fearfulness and a better human–
animal relationship compared to hens from other 
systems. A review by Nicol noted that fearfulness 
might be better correlated with the quality of 
human contact that hens are exposed to more 
142 O. Zorman Rojs, A. Dovč, H. Hristov, M. Červek, B. Slavec, U. Krapež, Z. Žlabravec, J. Račnik, M. Zupan
than with rearing systems (10), which may also be 
the case in our study.
This study is the first to provide results of 
welfare indicators of commercial layers in Slovenia. 
We cannot assume that our restricted sample of 
flocks is representative for the commercial hen 
industry in Slovenia, but it offers some estimation 
of the problems that may exist, such as keel bone 
damage.
Acknowledgements
This work was financially supported by the 
Slovenian Ministry of Agriculture, Forestry, and 
Food and the Slovenian Research Agency, project 
number V-4 1604.
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OCENA DOBROBITI V INTENZIVNIH REJAH KOKOŠI NESNIC V SLOVENIJI
O. Zorman Rojs, A. Dovč, H. Hristov, M. Červek, B. Slavec, U. Krapež, Z. Žlabravec, J. Račnik, M. Zupan
Povzetek: Opravili smo prvo celovito oceno dobrobiti kokoši nesnic v Sloveniji. V raziskavo smo vključili nesnice iz štirih različnih 
sistemov reje in raven dobrobiti ocenili v dveh starostnih obdobjih; na začetku nesnosti, v starosti od 22 do 24 tednov in pri 50 do 
55 tednih. Nesnice so bile rejene v obogatenih kletkah, v voljerah, v talni reji brez možnosti izpusta in v talni reji z možnostjo izpus-
ta. Ob vsakem ocenjevanju smo jate klinično pregledali in s pregledom posameznih živali ocenili specifične indikatorje dobre-
ga počutja (poškodbe prsnice, operjenost, poškodbe podplatnih blazinic, deformacije kljuna in poškodbe grebena ter kože). 
Plašnost kot indikator socialnega obnašanja smo ocenili s testom novega predmeta in s testom odmika od človeka. Spremljali 
smo tudi mikro-klimatske pogoje reje.
Ves čas spremljanja nismo ugotovili vidnih kliničnih znakov kužnih obolenj. Rezultati meritev mikro-klimatskih parametrov nakazu-
jejo, da so bili pogoji v rejah dobri. Poškodba prsnice se je izmed specifičnih kazalnikov izkazala za najresnejši problem, na katere-
ga vplivata tako starost kot sistem reje (p < 0,05). Poškodbe prsnice so bile značilno bolj izražene pri kokoših iz obogatenih kletk 
in voljer (p < 0,05) v primerjavi z nesnicami iz talnih rej. Kokoši iz talnih sistemov so bile tudi boljše operjene in so imele nižjo preva-
lenco poškodb na podplatnih blazinicah. Nesnice, ki so bile rejene v voljerah na družinski kmetiji, so kazale največ zanimanja za 
nove predmete in človeka. Te kokoši so bile ocenjene kot najmanj plašne in so izražale boljšo interakcijo človek–žival kot kokoši iz 
drugih primerjanih sistemov.
Ključne besede: kokoši nesnice; dobrobit; zdravje; sistem reje