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Animal Husbandry & Dairy Science
Review Article
Copyright © All rights are reserved by Arda Aydin
Leg Weaknesses and Lameness Assessment Methods
in Broiler Chickens
Arda Aydin*
Department of Agricultural Engineering and Technologies, Faculty of Agriculture, Canakkale Onsekiz Mart University, Turkey.
*Corresponding author: Arda Aydin, Department of Agricultural Engineering and
Technologies, Faculty of Agriculture, Canakkale Onsekiz Mart University, Turkey.
Received Date: November 23, 2018
Published Date: December 14, 2018
Abstract
In this study, firstly, a brief evolution of the chickens was mentioned and then ‘leg weakness’ and what leg weakness means in the
broiler sector were investigated. “Leg weakness” is a vague term used to describe properties of infective and non-infective nature
that occur in modern, fast-growing broilers. Modern broilers commercially grown are prone to foot problems, including lameness,
footpad dermatitis and hock-burn. Lameness is an extensive term used for some damages of broiler chickens with infective and
non-infective source. Lameness is a very big problem in the broiler industry. For the United State in 2002, the costs of lameness
were predicted to be between $80 million and $120 million. However, in literature, it has been proven that the lameness strongly
correlated with weight, growth rate and activity. The time before the chick reaches, a live weight of 1500 g was reduced from 120
days to 30 days in 80 years. As results of fast growing, severe problems have been occurred in broiler chickens. For example, the
animals with severe problems have a reduced feed efficiency and lower growth. The carcass quality of these animals has also been
decreased in value. Additional to the welfare problems that have been caused by leg problems, also financial losses have been
occurred for the producers. Therefore, the first purpose of this study is created as to review the leg weaknesses of broilers and
provides to readers a brief discussion of the factors influencing this problem. The second purpose of this study is to review the
lameness and lameness assessment methods for broilers. Additionally, the advantages and disadvantages of these methods are
discussed. At the end of this review, brief conclusions can be found with related reference list.
Keywords: Precision livestock farming; Broiler; Lameness; Chicken; Technology; Image analysis; PLF
Introduction
The poultry industry has grown enormously over its fifty-year
history until these days and now more than 20 billion broiler chickens
are produced every year. The demand for increased growth rate
and production due to the economic benefits of higher body weight
has led to the differential growth of body parts like accelerated
growth of muscle [1]. However, this growth is not accompanied by
the skeletal development. Lame broilers cannot walk easily and
unfortunately, they cannot reach the feeder and the drinker when
they are hungry or thirsty. Lameness is reducing their life quality.
The existence of lameness is strongly correlated with weight and
rapid growth of broilers [2]. Furthermore, movement problems
may be painful for the broilers. It can decrease the broiler’s activity
and increase different problems, like hock burns and chest dirtiness
[3]. Rapid growth rate accompanied by adequate nutrition, proper
management, optimum lighting and temperature, a disease-free
environment prevents weakness in broiler chickens. The absence
of any of these factors combined with the intrinsic weight bearing
characteristics give rise to the different degrees of leg disorders
[1]. Leg weakness can be classified as infectious, developmental
metabolic and degenerative disorders. Leg weakness leads to high
incidence of morbidity than mortality [1]. However, the disabled
bird experiences pain, does not reach feed and water and dies due to
inanition [4,5]. Therefore, the first purpose of this study is created
as to review the leg weaknesses of broilers and provides to readers
a brief discussion of the factors influencing this problem. Among
the factors that cause the leg weakness, include nutritional deficits,
mechanically induced trauma, toxins, genetic defects, pathogens
infectious diseases, sex, weight and growth rate, age, the efficiency
of feed conversion, handling and movement. The second purpose
of this study is to review the lameness and lameness assessment
methods for broilers.
This work is licensed under Creative Commons Attribution 4.0 License AAHDS.MS.ID.000506.
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Leg weaknesses
The changes in diet were increased the nutritional and physical
density of broilers. Higher nutrient intakes a combination of these
two factors has ensured that the growth rate has dramatically raised
in broilers [6]. The time before the chick reaches a live weight of
1500 g was reduced from 16 weeks to 4 weeks in order to utilize
this genetic potential for growth are good highly concentrated feed
in pellet form and extensive lighting schedules required. Along with
a selection for rapid growth to rap to achieve, a high body weight
has also been selected for the construction of more breast muscles.
This changes the conformation of the chicks, and this can give rise
to bone abnormalities [7]. Additional to the welfare problems that
are caused by leg problems will also occur a financial loss for the
producer. The animals with severe problems have a reduced feed
efficiency and lower growth. The carcass quality of these animals
will also decrease in value [8].
Occurrence
Most cases of lameness in broilers due to skeletal abnormalities,
but it is hard to describe. Cost and losses thereby accurately bone
abnormalities may lead to an increase in the mortality rate, “the
cull”, the percentage of rejected chicks and the “downgrades from
trimming” [1]. Losses by skeletal abnormalities in broilers are
significant [9]. In some stables there have up to 90 percent of the
birds some degree of lameness in slaughter age [10] and about 30
percent of the birds are simply too severely crippled [11].
Changes in behaviour
The bulk of the day of a roaster is lying spent. A quarter of this
time seem the chickens to sleep and more than half of the time
they are just not doing anything. A healthy chicken is on average 76
percent of the time spent lying. This percentage is increased with
age, and it is indicated that it is significantly larger with a higher
degree of lameness (up to 86 percent).
Types of Defects
The lameness problem of broilers is not only caused by
malformations or infection. Heavy, birds, which have no apparent
disease, walk like she is suffering and prefer to stay. That may
indicate the pain is related to the body weight and the pressure on
the bones and tissues [6].
Bone abnormalities
Bone abnormalities may be caused in various ways such as
nutritional deficits, mechanically induced trauma, toxins, and
genetic defects. All these factors play a greater role in the fastgrowing chicken breeds. They need for their rapid growth. More
and more specific nutrients they are more susceptible to trauma
because their bones are not fully developed. So, bone abnormalities
are common in the production of commercial broilers.
Valgus-varus
Valgus deviation results in a “knock-kneed” appearance. The
tars metatarsus deviates laterally when she is placed with the
tibiotarsus in a line. It is the most common form of long bone
defects, and it is quite serious [9]. This deviation results in a ‘bow-
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legged’ appearance. The tars metatarsus differs in now wondering
if she is placed with the tibiotarsus on a line. This deviation is less
common but leads to severe walking difficulties [9].
Tibia dyschondroplasia (Td)
TD seems to be a decoupling of growth plate chondrocyte
proliferation during endochondral calcification leg extension and
the result [9].
Rickets
This is probably the best-characterized bone disease in poultry.
It happens when bone mineralization is reduced. It is commonly
caused by a deficiency of calcium and phosphorus or an imbalance
between these [9]. ‘Rickets’ can occur in both fast-and slow-growing
chicks, but it is made worse by a greater need for nutrients in the
growth.
Femoral head necrosis
This syndrome, the causes of which are unknown, may affect the
entire house. The clearest indicator is the inability of the broilers to
stand up. When there is an autopsy is carried out on the birds, it is
the end of the femur. The broilers can respond to vitamin D3 in the
drinking water, but this method does not work every time [9].
Chondrodystrophie
Poultry with a shortage of water-soluble vitamins can develop
shorter bones with varus abnormalities. If the deficiency is too
much, the gastronomies tendon of the supporting can slip cartilage
[9].
Contact dermatitis
Feet burns, lesions that can be summarized under the heading
of contact dermatitis have risen in recent decades in broilers. It is
believed that contact dermatitis is caused by the effect of ammonium
chemical burning of the urea in the litter. There is also evidence
that the incidence and severity of contact dermatitis reflects on the
quality of the litter and the air, so actually on welfare aspects other
than pain [12]. Contact dermatitis is clear due to very long time
spent for sitting and bad litter. The time that is spent for sitting and
lying by the chicks, increases with the age from 75 percent in the
first week to 90 percent at five weeks [5]. Footpad dermatitis is a
type of contact dermatitis, which is characterized by lesions on the
soles of poultry. In severe cases, there is a swelling and necrotizing
tissue occurs or can be observed. This can lead to a problem in the
food hygiene because these lesions may be used as entrance road
for bacteria. This then leads to a poorer carcass quality [13].
Infectious Diseases
Pathogens
The main pathogens that can cause lameness are Reovirus,
Mycoplasma sinoviae, Staphylococcus aureus and Retroviruses.
Reovirus
Avian reoviruses, which causes of viral arthritis / tenosynovitis
(inflammation of the tendon sheath), are widespread in the broiler
industry. It is suspected that the virus can spread through ‘avian egg
Citation: Arda Aydin. Leg Weaknesses and Lameness Assessment Methods in Broiler Chickens. Arch Animal Husb & Dairy Sci. 1(2): 2018.
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transmission’, especially since the virus was found in apparently
normal embryos from commercial chickens. The clinical picture is
characterized by mild to moderate lameness; swollen ‘hocks’ met a
noticeable increase of fluid in the “hock” joints [14].
Mycoplasma synoviae
of feed conversion, nutrition, handling and movement. These
factors will be discussed further below. The key factors here of
non-infective and non-nutritional bone abnormalities its genetic
selection and the management [22].
Invisible Mycoplasma Synoviae causes respiratory diseases
but can also result in airsacculitis and synovitis in chickens and
turkeys. The effects of M. synoviae were first established in the 50s,
it was still identified for the organism. Characteristic of M. synoviae
is the difference in pathogenicity between different strains. Of
these, seemingly cause no trace of disease to those diseases of the
respiratory tract and/or synovitis [15].
The rapidly increasing weight will require more of the
immature skeleton and the shape change can alter the forces, which
are produced during the run. The high ‘Gait Score’ in broilers may
thus be the consequence of pain, biomechanical problems, or both
[23]. [24] investigated the relationship between lameness, weight,
growth rate and age. The results indicated that weight and growth
rate were important factors for lameness [24].
Among the most important retroviruses, include the avian
leucosis viruses. They are divided into several subgroups. Avian
leucosis virus subgroup J (ALV-J), this is one of the most economically
important pathogens in broilers. The nodes consist of myelocytes
with characteristic eosinophilic cytoplasmic granules. There may
be other types of lesions occur as long sarcoma’s abnormal feathers
and infiltration of myelocytes in the bones and the periosteum of
the sternum and the ribs [16].
Both sexes have problems of lameness. However, the male
chicks encountered more problems than the female, even when the
body weight is considered. The ‘gait score “of the males was about
half a’ gait score ‘unit higher [25].
Retroviruses
Staphylococcus aureus
Staphylococcus aureus is a major cause of illness in the
broiler industry. Infection with S. aureus can cause many different
clinical features such as septicemia (prevention of pathogenic
microorganisms and their toxins in the blood), bone and joint
infections, abscesses and dermatitis. Such diseases bring
animal welfare compromised and cause economic losses due to
downtime, reduced productivity, and carcass contamination in the
slaughterhouse [17].
Mycotoxins
Mycotoxins are one of the nutritional factors causing skeletal
disorders such as Rickets, Articular Gout and Tibia Dyschonroplasia
and the list various bone diseases in broilers possibly caused by
mycotoxins [1]. Mycotoxins such as aflatoxin, ochratoxin and
fusarium toxin lead to rickets due to their toxic effects on liver and
kidney, which consequently prevents the conversion of vitamin D3
and its absorption [1].
Lameness
According to the European Commission report lameness is
the main cause of bad welfare in broiler chickens [18]. Lameness
is an extensive term used for some damages of broiler chickens
with infective and non-infective source [19]. Lameness is also a
very big problem in the broiler industry. The financial losses due to
lameness in the commercial grown broilers are considerable [20].
For the United State in 2002, the costs of lameness were predicted
to be between $80 million and $120 million [21].
Causes of Lameness
Among the factors that cause lameness, include infectious
diseases, genetics, sex, weight and growth rate, age, the efficiency
Weight and growth rate
Gender
Genetics
There is evidence that there are differences in the occurrence
of ‘leg weakness’ between several commercial breeds that perform
the same for the rest [10]. Genetically different genetic experiments
have shown that the cause lameness bone abnormalities which
possess a certain degree of heritability [26]. It appears that
lameness is more common in some breeds than others are. Positive
selection against these characteristics, it is therefore possible [26].
Age
The investigation of [25] found that the ability to walk properly
deteriorated with age. At the age of four weeks, the chickens could
still run well. Less than 1 percent of these birds had a gait score
of 4 or 5 on 6 weeks of age the broilers were significantly worse
walking and at 7 weeks they could run worse. The speed at which
the deteriorated chicks between 4 and 6 weeks was larger than that
between 6 weeks and 7 weeks [25].
Food (Nutrients)
It has been shown that nutrients are important for the normal
skeletal development. A well-balanced diet is essential in broilers
to prevent leg disorders. For example, a shortage of water-soluble
vitamins, manganese, or zinc may lead to the development of
shorter bones with valgus abnormalities. In addition, ‘rickets’ can
be exacerbated by a lack of nutrients in fast-growing chickens [6].
Small shortages of biotin in feeding schedules caused more footpad
dermatitis [27].
Composition and feeding schedule
A reduction of the growth rate by means of the restriction of
feed can reduce the occurrence of bone abnormalities, which are
not caused by an infection. It could be that food restriction works by
slowing the growth rate of the muscle tissue, thereby increasing the
growth rate of the bone tissue. [31] Conducted a study to determine
whether a manipulation of the feed pattern or early feeding pattern
would have effect. Fewer meals per day were associated with a
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lower incidence of TD, less “hock burn, a better gait, lower body
weight and better feed conversion. [4] Suggested that this was due
to a better-organized feeding pattern, resulting in more activity.
Management
Management consists of many different factors, such as bedding,
ventilation, heating, lighting diagrams, nutrition, occupation,
enrichment of the cages. According to management, consultants are
deficiencies in these factors, the main cause of the high incidence
of foot pad dermatitis. It is advised to producers to increase the
ventilation and start relatively early. It is also recommended to
use thin layers of litter and sometimes change from straw to wood
shavings. It would be easier to scrape the chickens, and it can more
easily be kept dry and ventilated [13].
Litter
When housing poultry litter on the ground is well important.
A good litter material can be defined as a material that can absorb
and give off a lot of moisture back. In practice, wine wood shavings
and straw, the most commonly used materials [30]. It was also
reported all that chicks that sit on wood shavings show higher
activity than those sitting on straw. This could also be an occasion
for less lameness [31].
Conditioning (Heating and Ventilation)
The high and low temperature is associated with increased
incidence of leg disorders. At a low occupancy is apparent that the
air has little influence on the chick quality. At a higher occupancy
(20 chicks per m2), however, the climate has an influence: the
proportion chicks with diseased feet are lower and they are less
soiled [30].
Light
The broiler industry is continuing illumination or nearly
continuous illumination (23 h light: 1 h dark) standard to increase
the food intake and growth rate [22]. The light can have an influence
on behavior, physiology and well-being in different ways. There
are studies that have shown that lameness and growth of chicks is
influenced by different light periods [31].
Occupancy
The use of high occupancy is far-reaching to economically
maximum advantage. Use of the surface however, the capacity is
limited by the bad effects that this has on the growth and quality.
The occupation has a clear influence on the external quality of the
chicks. In the lower occupancy of 16 chicks per m2 is the number
of chicks with red heels considerably lower and annotating of the
soles is significantly less. Moreover, there are fewer varieties for the
chicks less soiled at low stocking densities [30].
Enrichment
It was proved that birds, which were trained less bone
abnormalities exhibited from 33 days [5]. The sober environment
can contribute to moving the little chicks. There are different
attempts have been made to enrich the surrounding area.
Enrichment of the broiler house can contribute to greater activity,
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and it can improve the bones of chickens, including their welfare
[5].
Assessment of lameness
Traditional methods to determine the gait score as an indicator
for lameness include manual scoring of birds’ movement and
other behaviors in the farm. Nevertheless, it is difficult to score the
behaviors of broiler chickens. Compared to traditional methods,
fully automated image analysis techniques have many potentials
for lameness assessment. Automatic video image technique to
analyze the activity as an indicator of lameness in broilers is
becoming popular [30] because it is getting cheaper. It is also noncontact method, which allows recording more frequent data during
the life span of broiler chickens. There is also no need for huge
data storage when data are automatically evaluated in real-time
[30]. The measurements can also be performed continuously and
automatically throughout the life span of birds with non-invasive
and non-intrusive way. It is also do not involve the biosecurity risk
of having people visiting different commercial farms to perform
visual gait scoring for boiler chickens [31].
Manual assessments (Gait scoring system)
The first manual assessment technique was developed by [32]
to evaluate the gait problem in birds by visually observing and giving
some gait scores for each broiler chicken. In this method, a score is
assigned ranging from zero (no leg problems) to five (completely
paralyzed) according to the criteria as follows. 0 (healthy broiler);
1 (the broiler moves fast, but there is a slight walking deficiency);
2 (the broiler moves fast, but significant walking deficiency is
observed); 3 (the broiler moves fast, but there is a significant
deficiency); 4 (the broiler cannot move fast and there is a serious
difficulty); and 5 (the broiler cannot move anymore).
Bristol scoring system
The University of Bristol’s Gait Scoring Guide is widely used
to assess walking ability. This scoring system works on the same
principle as the Gait Scoring System. Here, too, each broiler again a
score from 0 to 5 according to certain criteria. The score is awarded
by experts [32]. Although this method is often used because it is so
easy to apply, it is still very subjective. It depends on the expertise
and experience of the observer. Other studies showed that the
repeatability of the visual gait score is not entirely reliable. From
other studies even more important are that only the movement
scored with this method, and not the pressure exerted by the chick.
It will therefore not give objective information on whether the
animal is in pain or not [33].
Automatic Assessment Systems
Pedobarograph system
The light intensity will be in proportion to the applied pressure
[33]. The gait-analysis was performed using a purpose-built
pedobarograph. When pressure is exerted on the surface, the
emulsion side of the photographic paper pressed closer against the
glass so that the light is distributed. This can be seen on the bottom
of the glass. The glass plate and the career were both covered with
Citation: Arda Aydin. Leg Weaknesses and Lameness Assessment Methods in Broiler Chickens. Arch Animal Husb & Dairy Sci. 1(2): 2018.
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polythene-backed protective sheeting “(Benckhote, Whatman
International Ltd) in order to ensure the birds. For a homogeneous
surface under the glass is a mirror placed at an angle of 45 degrees.
The divided light is reflected by the mirror and filmed with a closedcircuit camera (Panasonic WV-BP3101B0). The video was recorded
on a S-VHS recorder (Panasonic AG-7355), and images warden
transferred to a Powermac 8100/110 computer with a Scion LG-3
frame grabber card and analyzed using Scion Image (version 1.57)
software (Scion Corporation, Maryland, USA). In this study, there
were 12 frames per second. Each pixel is given a value between 1
and 254, depending on the brightness of that point. The system can
then be calibrated to relate with applied pressure [34].
There were several gait parameters measured and compared
between the different groups:
•
Speed (m/sec)
•
Step width
•
•
•
Step frequency (steps/min)
Step length
Step angle
Video recordings
In another study, the behavior of broiler chickens related with
lameness was investigated by [16]. Comparisons were performed
between healthy broilers and lame birds between 39 and 49 days
old. Healthy birds spent 76% of their time as lying and 24% of their
time as standing and/or moving. Lame broilers with gait score 3
spent 86% of their time as lying in. Lying events were also increased
with the age of broilers [16].
Latency to lie test
In broilers, another method for lameness assessment was
described by [35]. The time duration that birds stayed standing in
water was measured and the results were checked with traditional
results. There was an important (P < 0.001) correlation among the
gait scores and LTL of birds. More than 750 birds at the age between
32 and 45 days old were tested in a broiler house. Almost all of the
healthy broilers were able to stand for at least 15 minutes and most
of the lame broilers sit down in five minutes.
Force plate study of avian gate
Another method was developed by [36] to define the ground
reaction force of birds. The ground reaction force was tested
while the broilers walked on the experiment setup. GRF patterns
represented important changes during growth. It was concluded
that the force plate is an appropriate study tool for recording the
ground reaction force patterns of broilers.
Precision livestock farming approaches to detect the
lameness of broilers
Automatic monitoring the activity in broiler chickens is one
of the easiest ways to define lameness at broiler houses. A fully
automated monitoring system was developed by [37] to measure the
broilers activity at different gait scores. The activities were obtained
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by using an automatic video recording system. Then, the images
of the birds with six different lameness level were automatically
analyzed by the developed algorithm. The results showed that,
there was an important correlation among the lameness obtained
by expert and activity recorded by image monitoring tool [37]. It
was also detected that there was an important lower activity of
high gait score broilers (GS4&GS5). Therefore, it was concluded
that, this technique can be used as indicator of high lameness level
(GS4&GS5) in broiler houses. Another study was performed by [30]
to define a new technique to estimate the spatial use of broilers by
using image analysis. An important relationship was observed for
both experiments among the lameness and the movement recorded
by the image monitoring tool. The results also showed that there
was a strong relationship between the spatial use of broilers with a
certain lameness level and activity. Therefore, it was also concluded
that the spatial use of broilers can also be a kind of indicator for
activity and criteria for lameness assessment [30].
Conclusion
As explained in this study, leg weakness includes a wide range
of abnormalities due to a multitude of etiological causes. It is
definitely affecting the growth and end-weight of broiler chickens
consequently causing a huge economic loss to the farmer. As
detailed above, the leg weakness of broiler chickens is influenced
by many different factors, which needs to be considered when
managing broilers. Leg weakness can be prevented by modifying
the environment and diet. In addition, growth rates can be reduced
by artificial lighting and restricted feeding. However, proper
manage mental practices should be adopted [38-51].
Acknowledgment
None.
Conflict of Interest
No Conflict of Interest.
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