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Selection for fast early growth rate and feeding and management procedures which support growth have lead to various welfare problems in modern broiler strains. Problems which are directly linked to growth rate are metabolic disorders causing mortality by the Sudden Death Syndrome and ascites. Fast growth rate is generally accompanied by decreased locomotor activity and extended time spent sitting or lying. The lack of exercise is considered a main cause of leg weakness, and extreme durations of sitting on poor quality litter produces skin lesions at the breast and the legs. Management factors which slow down early growth alleviate many welfare problems. Alternatively it may be considered to use slow growing strains which do not have the above mentioned welfare problems. Since growth is a main economical factor, there are problems of acceptability of these measures in the commercial broiler production. Stocking density is a central issue of broiler welfare. It is evident, that the influence of stocking density on growth rate and leg problems acts through its influence on litter and air quality. High moisture content of the litter enhances microbial activity, which in turn leads to increase of temperature and ammonia in broiler houses, and thus, high incidence of contact dermatitis. High stocking density impedes heat transfer from the litter surface to the ventilated room. This restricts the efficacy of conventional ventilation systems in alleviating heat stress. Lighting programmes with reduced photoperiods are considered essential for the stimulation of locomotor activity and the development of a circadian rhythm in the birds. Extended dark periods, however, reduce growth when applied in the first weeks of age. Compensation occurs when the time of the production cycle is substantially increased. Various methods to enrich the environment have shown only moderate effects on the behaviour and physical conditions of broilers.
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© World’s Poultry Science Association 2006
World’s Poultry Science Journal, Vol. 62, September 2006
Received for publication November 25, 2005
Accepted for publication January 24, 2006 455
DOI: 10.1079/WPS2005108
Welfare of broilers: a review
University of Hohenheim, Institute of Animal Husbandry and Breeding (470), D-
70593 Stuttgart, Germany
Selection for fast early growth rate and feeding and management procedures which
support growth have lead to various welfare problems in modern broiler strains.
Problems which are directly linked to growth rate are metabolic disorders causing
mortality by the Sudden Death Syndrome and ascites. Fast growth rate is generally
accompanied by decreased locomotor activity and extended time spent sitting or
lying. The lack of exercise is considered a main cause of leg weakness, and extreme
durations of sitting on poor quality litter produces skin lesions at the breast and the
legs. Management factors which slow down early growth alleviate many welfare
problems. Alternatively it may be considered to use slow growing strains which do
not have the above mentioned welfare problems. Since growth is a main economical
factor, there are problems of acceptability of these measures in the commercial
broiler production. Stocking density is a central issue of broilerwelfare. It is evident,
that the influence of stocking density on growth rate and leg problems acts through
its influence on litter and air quality. High moisture content of the litter enhances
microbial activity, which in turn leads to increase of temperature and ammonia in
broiler houses, and thus, high incidence of contact dermatitis. High stocking density
impedes heat transfer from the litter surface to the ventilated room. This restricts the
efficacy of conventional ventilation systems in alleviating heat stress. Lighting
programmes with reduced photoperiods are considered essential for the stimulation
of locomotor activity and the development of a circadian rhythm in the birds.
Extended dark periods, however, reduce growth when applied in the first weeks of
age. Compensation occurs when the time of the production cycle is substantially
increased. Various methods to enrich the environment have shown only moderate
effects on the behaviour and physical conditions of broilers.
Keywords: broilers; welfare; behaviour; management; leg problems
As a result of intensive selection for fast early growth, the poultry breeds and lines used
for meat production differ substantially from egg producing breeds in their anatomy,
physiology and behaviour. Feeding and management for meat production has been
developed concurrently to exploit the genetic potential for growth. The time required to
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456 World’s Poultry Science Journal, Vol. 62, September 2006
Welfare of broilers: W. Bessei
reach 1.500 g live weight was reduced from 120 days in 1925 to 30 days in 2005 (Albers,
1998). In order to exploit the high genetic potential for growth highly concentrated diets
fed in pellet form and extended lighting programmes are required. The main welfare issues
which have been addressed in the last two decades are closely linked with the fast early
growth rate: high susceptibility to metabolic disorders and low locomotor activity. Among
the management measures which have elicited criticism from the welfare point of view are
in first line stocking density, litter quality and ammonia concentration in the air. In
addition inadequate light duration and intensity and lack of environmental stimuli are
considered to compromise welfare conditions. Most of the welfare problems are caused by
multiple genetic and environmental factors and their interactions. Therefore it is generally
not possible to strictly attribute particular problems to particular genetic or management
factors. In the following the welfare problems are categorised in those which are mainly
related to the genetic line and mainly to environmental factors.
The basic welfare issues in meat producing poultry are similar for the different species.
As broiler chickens represent the major part of poultry meat in Europe and world wide,
and most of the research on welfare has been done on broilers, the present overview is
limited to chickens. It is expected, however, that more emphasis will be placed on the
welfare of other poultry species in the future.
Genetic issues
Slow growing breeds show lower mortality from day-old to slaughter age, although the
duration of the fattening period is shorter in the latter (Bauer et al., 1996). Causes of
mortality related to fast growth are mainly Sudden Death Syndrome (SDS) (Gardiner et
al., 1988) and ascites (Maxwell and Robertson, 1997). With regard to SDS fast growing
male birds are generally more affected than females (Grashorn et al., 1998). Although the
physiological mechanisms causing SDS are not fully understood, there is no doubt that
growth rate represents the most eminent cause for this problem. As expressed in the name
of the syndrome birds which are otherwise in good condition die within a short time. The
range from the first sign of unrest until death was from 37 to 69 seconds (Newberry et al.,
1987). Hence suffering of the birds is restricted to that period. The welfare situation is
different in the case of ascites. Ascites develops gradually and the birds suffer for an
extended period before they die. The disease is characterised by hypertrophy and
dilatation of the heart, changes in liver function, pulmonary insufficiency, hypoxaemia
and accumulation of large amounts of fluid in the abdominal cavity (Riddel, 1991). The
underlying problem of these symptoms is insufficiency of oxygen supply of the tissues of
rapidly growing broilers, and both genetic and environmental factors contribute to the
development of the disease. There exists genetic variation of the susceptibility to ascites
between and within broiler lines (Deeb et al., 2002). Broilers which are susceptible to
ascites showed a reduced function of the tissues mitochondria (Cisar et al., 2005).
Environmental factors, which increase the demand for oxygen, such as low brooding
temperature, or, which impair oxygen supply to the blood, such as high altitude, are known
to increase the incidence of ascites (Mitchell, 1997; Julian, 2000).
There is a high incidence of skeletal disorders in commercial broilers. Most of them are
found in the locomotor system. Although diseases and nutritional deficiencies may play a
role in the development of leg problems as well, the influence of growth must be
considered as the main factor. Among the leg problems varus and valgus deformities,
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osteodystrophy, dyschondroplasia and femoral head necrosis play a major role. It has been
found in experiments that the incidence of twisted legs and tibial dischondroplasia can be
reduced by genetic selection (Sørensen, 1989). Because of the negative correlation
between leg problems and growth rate this option may not be fully exploited in
commercial breeding programmes. The leg abnormalities impair the locomotor abilities of
the birds, and lame birds spend more time lying and sleeping (Vestergaard and Sanotra,
1999). Subjective gait scoring systems have been developed from 1 (normal gait) to 5
(high walking problems) to assess the incidence of leg problems in broiler flocks (Kestin
et al., 1992) and it has been assumed that the welfare of birds is poor when the scores are
3 or higher (McGeown et al., 1999). Walking in birds with poor gait scores was
significantly improved after treatment with analgesic and anti-inflammatory drugs. In
self-selection experiments lame birds selected more drugged feed than intact birds
(Danbury et al., 2000). This lead to the assumption that leg problems in broilers are
painful. The proportion of broilers with gait scores of >3 varies from 3 to 30 percent (EU,
2000). In a survey including 29 broiler flocks Sanotra et al. (2001) reported an average
incidence of 30 per cent with a gait score of 3 or more, ranging from 12 to 55 per cent. The
variation of the data may by explained by the effect of the scoring personal rather than
differences in the flocks studied. There exist more objective methods of gait analysis in
birds using video-tracking or foot-print analysis (Reiter and Bessei, 1997; De Jong et al.,
2004). These methods, however, are highly complicated and time consuming, and thus,
not applicable when large flocks have to be controlled. It may be useful to develop a
scoring system which reduces the influence of the scoring personnel.
Hock burns, breast blisters and foot pad lesions which may be summarised under the
expression contact dermatitis, have been increased in broiler flocks during the last decades
(Hartung, 1994). They are characterised by hyperkeratosis and necrosis of the epidermis
of the affected sites. In an advanced stadium there are inflammations of the subcutis with
degeneration of tissue. Secondary infections (e.g. E. coli) may further worsen the
conditions of the birds. There is evidence that the contact dermatitis cause pain and thus is
a matter of welfare. The incidence has found to be highly variable. Surveys in Sweden
have reported an average prevalence of 5 to 10% (Elwinger, 1995; Berg, 1998) with high
variation among flocks.
Contact dermatitis is obviously the result of the extremely long time of sitting and poor
litter quality. Sitting and lying in fast growing broilers increase with age from 75% in the
first week to 90% at 5 weeks of age (Bessei, 1992a).
Locomotor activity is important for the ossification of the bones of growing animals.
There is a causal interrelationship between fast growth, low locomotor activity and leg
problems. Thorp and Duff (1988) exercised broilers four times for 15 minutes per day
starting at 8 days of age. This reduced the incidence of leg abnormalities from 33 days of
age onwards. Reiter and Bessei (1994; 1995) have shown that the walking ability of fast
growing broilers on a treadmill was higher than the voluntary activity under home pen
conditions, and the increased exercise improved the skeletal conditions of the legs. The
voluntary locomotor activity of fast growing broilers was significantly increased when a
part of the body weight was alleviated by a special suspension device (Rutten et al., 2002).
This treatment improved bone characteristics as compared to the control broilers without
exercise. The importance of exercise differs among breeds. In a recent experiment birds of
a slow and a fast growing broiler line were brought to the same load on the legs by putting
weight on the slow growing and alleviating weight of the fast growing lines (Djukic et al.,
2005). As before, the alleviation of weight from the fast growing lines increased
locomotor activity and improved the leg bone conditions. Loading weight on the slow
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growing broilers decreased the locomotor activity. But the bone structure and walking
ability was not significantly changed.
Environmental issues
Stocking density is a key issue for the economical result of broiler production. Current
recommendations for stocking density in broilers differ widely by country and
organisation (Table 1). There are plenty of experiments covering a wide range, from less
than 10 to over 80 kg/m2floor space. Highest stocking rates of more than 80 kg/m2have
been reported in caged broilers by Andrews (1972). In deep litter systems maximum
stocking densities of about 50 kg/m2have been tested by Shanawany (1988) and Grashorn
and Kutritz (1991). Most other experiments ranged between 20 and 40 kg (Scholtyssek
and Gschwindt-Ensinger, 1983; Scherer, 1989; Wiedmer and Hadorn, 1998). There is a
well documented reduction of feed intake and reduced growth rate when stocking density
exceeds about 30 kg/m2under deep litter conditions. The effect of stocking density was
reduced, when broilers were kept in cages (Scholtyssek, 1973) or on perforated floors in
combination with under-floor ventilation (von Arkenau et al., 1997). The negative effect
of stocking density on growth rate was partially compensated by increased ventilation
rates (Grashorn and Kutritz, 1991). These results lead to the assumption that problems of
dissipating the metabolic heat may be the causal factor for the depression of growth rate.
This was confirmed by a study on the temperature of the litter (Reiter and Bessei, 2000)
(Table 2). The temperature measured 5 cm underneath the litter surface increased from
23.3 to 31.3 centigrade as stocking density increased from 19 to 40 kg per m2. The
temperature 1 m above the litter was about 22 centigrade and not influenced by stocking
density. The assumption that the negative effect of stocking density on growth is caused by
heat stress has been confirmed by McLean et al. (2001). They found that deep panting in
broilers was increased when stocking density increased from 28 to 34 and 40 kg/m2,
suggesting more thermal discomfort from 34 kg onwards. The increase of litter
temperature with increasing stocking density can be explained by different effects. Higher
stocking density increases nitrogen and moisture level in the litter and thus, improves the
conditions for the microbial activity. The transfer of heat from the litter surface to the
ventilated space is inhibited when, at the end of the growing period, the total area of the
floor is covered by the birds. Petermann and Roming (1993) measured the area covered by
broilers in response to their body weight. Based on these data the percentage of the area
covered by the birds was calculated. The area was totally covered at densities of 42, 45 and
48 kg/m2when the live weight of the broilers increased from 1.5 to 1.9 and 3.2 kg
There was no consistent trend of stocking density on feed conversion rate. While this
trait was improved (Scholtyssek and Gschwindt, 1980; Shanawany, 1988; Grashorn and
Kutritz, 1991; Cravener et al., 1992) or not significantly changed in some cases
(Scholtyssek and Gschwindt-Ensinger, 1983; Waldroup et al., 1992), there was a
significant deterioration reported by Scholtyssek (1974).
The occurrence of morphological changes, such as dermatitis including food pad
lesions, breast blisters and soiled plumage have been reported as a result of high stocking
rate. Most of the experiments have shown that the prevalence and incidence of these
damages increased with increasing stocking rate (Weaver et al., 1973; Proudfoot et al.,
1979, Cravener et al., Gordon, 1992). It seems, however, that as mentioned before, the
negative effects are the response to factors related to stocking density. When stocking
densities from 10 to 35 birds/m2were studied, the incidence of dermatitis, leg problems
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and soiled plumage varied with humidity of the litter and ammonia concentration, but not
with stocking density as such (Algers and Svedberg, 1989). In a large scale experiment
with commercial farms using different breeds, management systems and stocking
densities, it was confirmed that the management conditions (litter quality, temperature and
humidity) were more important than stocking density (Dawkins et al., 2004). Wet litter
and ammonia have been found to produce breast blisters and skin lesions (Harms et al.,
1977; Proudfoot et al., 1979; Valentin and Willsch, 1987; Weaver and Meijerhof, 1991;
Grashorn 1993). Wet litter was also identified as main factor for foot-pad dermatitis by
Ekstrand et al. (1997). In this context the type of the watering system showed a significant
effect. Interestingly the incidence of foot-pad dermatitis increased with thickness of the
litter layer.
It can be concluded that the influence of stocking density on the growth rate of broilers
is acting through heat stress rather than physical restriction of the animals` space for
movement. The results have shown that the growth depression which has been found with
increasing stocking density was closely linked to problems of heat dissipation. The effect
of stocking density on growth rate was reduced when the birds were kept on perforated
floors, or on litter floors in combination with under-floor ventilation High stocking density
impedes under conventional deep litter conditions, the heat transfer from the litter to the
ventilated space and increased ventilation rate will not entirely alleviate the problem of
heat stress. The negative effects of stocking density on different forms of dermatitis are
mediated through poor litter conditions.
Table 1 Some recommendations on stocking density in the EU.
EU (2000) Slaughter age, weight and ventilation rate / climatic condition should be
considered; it appears that welfare problems are likely to emerge when
stocking rates exceed 30 kg/m2
This stocking densities should only be allowed when the
producer is able to maintain air and litter quality
European Council (1995) no fixed figures
a.v.e.c. (1997) … stocking density depends on the housing capacity and
quality of equipment and standard of management
Danske Fjekraeraad (1997) maximum 40 kg/m2
FAWC (1992) 34 kg maximum stocking; should not be exceeded at any
Germany (Voluntary
Agreement, 1999) 35 kg/m2
Switzerland (Federal Law) 20 birds/m2or 30 kg /m2maximum
Sweden (Berg, 1998) 20 – 36 depending on management scoring
Table 2 Temperature in a broiler house at the end of a 6 weeks growing period in response to different
stocking densities and different locations (height over litter surface and underneath litter surface) (after
Reiter and Bessei, 2000).
Height over litter Stocking density (kg/m2)
surface (cm) 19,4 30,0 40,2
100 21,8 21,8 22,3
20 22,3 22,5 28,6
0 23,3 26,9 30,3
-5 23,3 26,9 31,3
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The effect of stocking density on locomotor and scratching behaviour in fast growing
broilers was increased when stocking density was increased from 10 birds/m2in small
groups, to higher densities in larger groups (Blokhuis and van der Haar, 1990; Lewis and
Hurnik, 1990; Bessei and Reiter, 1993). In other studies using larger groups only there was
no significant effect of stocking density on the behaviour with stocking densities varying
from 10 to 25 birds/m2(Scherer, 1989; Bessei, 1992a). Since the behavioural activities of
broilers decrease rapidly from 2 weeks of age onwards (Reiter and Bessei, 1995) the effect
of stocking density may become less important in this regard.
The barren environment may contribute to the low behavioural activities of broilers.
There have been various attempts to stimulate the behaviour by the enrichment of the
environment. Various methods have been examined, using litter, light programmes, toys,
sequential feeding programmes and perches or elevated platforms.
The availability of litter stimulates scratching behaviour. There is a sharp decline of
scratching activity with growing age in conventional broilers (Bessei, 1992a). It is
assumed that the deterioration of litter quality and the general decrease of the activity may
be causes of this effect, but the relative importance of both factors has not been elucidated
so far. The availability of litter did not modify locomotion as compared to an elastic
perforated floor (Bessei, 1992b). Arnould et al. (2001) observed an increase in activity of
young broiler chickens by providing strings and trays containing sand. The effect of the
enrichment disappeared with increasing age. There was no effect of the treatment on the
leg conditions. Mench et al. (2001) found significant improvements of behaviour
activities on leg conditions of broilers, when they were reared in enriched pens with
opportunities to climb, scratch and perch. Provision of perches is considered to stimulate
the activity of broilers. The use of perches is depending on the height from the floor and
the weight of the birds. Since heavy birds, which are considered to need the behavioural
stimulation, are making poor use of the perch, their effect on the locomotor activity is
rather limited. According to Martrenchar et al. (1999) less than 1% of broilers used
perches (20 and 33 cm high) at low stocking density (11 birds/m2). The acceptance of
perches was increased to 10% when the stocking density was raised up to 22 birds/m2.
More perching (22%) could be achieved by Davies and Weeks (1995) who adapted the
high of the perches, according to the growth of the birds, from 2.5 to 26 cm. Su et al.
(2000) found no effect of perches on gait score. According to our own observations
broilers used a ramp between feeder and drinker as perch, and spent more time sitting than
broilers without ramps (Bessei, 1992 b). Barriers between feeders and drinkers have been
reported to be used as perches (Bizeray et al., 2001). But gait score was not improved.
Some improvement of tibial breaking strength was reported by Balog et al. (1997) when
ramps were placed between feeders and drinkers, but there was no reduction of tibial
dyschondroplasia. Bokkers and Koene (2003) found that more slow growing than fast
growing broilers used perches. The use of perches produced breast blisters and
deformation of the keel bones.
Sequential feeding of diets containing different levels of lysine has been used to
stimulate the activity of broiler chickens (Bizeray et al., 2001). This procedure increased
the foraging behaviour and locomotor activity in the chicks and improved leg conditions.
At the same time, however, the body weight of the sequentially fed birds was reduced.
Briefly, environmental enrichment methods, which successfully stimulate the activity
can improve the leg conditions and, thus, the welfare state of broilers. Perches are poorly
used and do not increase the activity of the birds. While there was no impact of perches on
leg conditions, they obviously increased the incidence of breast blisters.
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Continuous light regimes allow the birds to feed continuously throughout the day.
Earlier experiments have shown that growth rate and feed conversion were better under
continuous light than under a natural day-night regime (Schutze et al., 1960; Morris,
1967). Short light-dark-rhythms produced similar effects on the performance as
continuous light (McDaniel, 1972; Buckland et al., 1973; Kondo et al., 1986). There was
a positive effect of extended dark periods with regard to leg problems, mortality and
metabolic disorders (Zubair and Leeson, 1996), but growth rate was reduced by this
treatment. It is known that chickens, under extended dark phases, develop a circadian
rhythm with increased feed intake before the beginning of the dark phase. It is also known
that broilers start eating in the dark, when extended dark phases are introduced. It seems,
however, that young broilers are not able to fully compensate for the shortened light
periods. Thomsen (1989) kept broilers at 12:12 hours (light: dark) from 3 to 21 days of age
and at continuous light thereafter. Growth rate was delayed under the 12:12 hrs light-dark
cycle. Full compensation occurred at 49 days of age only. When intermittent lighting of 1
hour light : 3 hrs darkness have been compared with nearly continuous light (23 hrs light:1
hr darkness) compensation of growth rate was observed in males, but not in females
(Buyse, et al., 1996). Sørensen et al. (1999) found reduced incidence of tibial
dyschondroplasia but no improvement of walking ability, when extended dark periods
where provided between 3 and 21 days of age.
It has been shown that the light programme influences the level and diurnal pattern of
the locomotor activity of the chickens. Simons and Haye (1978) measured the activity of
broilers under continuous and intermittent light regimes. The total activity was higher
when continuous light was given, and the activity was evenly distributed throughout the
day. Under intermittent lighting conditions using short light-dark-cycles episodes of high
locomotor activity occurred during the short light periods. These short periods of high
activity did positively influence leg conditions (Simons and Haye, 1978; Thomsen, 1989).
Reiter and Bessei (2002) measured the locomotor activity of broilers under quasi
continuous light (23 hrs light : 1h dark) and 16 hrs light : 8 hrs dark. The average activity
level in the light phase increased as the duration of light decreased. In the same experiment
it was shown that broilers under 23 hrs light : 1 h dark did not develop a circadian activity
patters, while those under 8hrs dark : 16 hrs light did. The development of circadian
rhythms is considered an important indicator of welfare in domestic animals. Therefore
clear day- night light programmes, which enable the expression of the diurnal rhythms,
play an important role in the recommendations of animal-friendly livestock systems. It
seems that more than one hour darkness is required for this purpose. 8 hrs of darkness
obviously allow the development of the rhythm, but it is not known so far, whether this is
the minimum time of light required. It has also to be considered in this context, that these
results are based on the activity of groups of birds. It is generally known that the light
cycles do not generate rhythms, but synchronise endogenous rhythms with different basic
frequencies. It is possible that individual circadian rhythms even under continuous light.
They may remain undetected in the group data because of lacking synchronisation.
The requirement for light was investigated by Savory and Duncan (1982) who trained
broilers to operate a light switch. When the birds were offered to switch the light on in a
dark environment (1 to 3 min of light per response) they realised a light period of about
20% of the time of day. When the programme allowed switching off the light in a light
environment the time of darkness was less than 1%, and when they could switch the light
on and off the duration of light was more than 80 percent of the time budget. Berk (1995)
reported that broilers, when they were given free choice between a light and dark, the time
spent in the dark increased with age.
Light intensity, wave length and source of light can influence the activity of broilers.
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High light intensity (180 vs. 6 lux) increased the locomotor activity and reduced leg
problems in 6 week old broilers (Newberry et al., 1988). The positive effect of light
intensity disappeared at 9 weeks of age. In another experiment using 2 and 200 lux tibial
bowing was higher at the high light intensity (Gordon and Thorp, 1994). Despite the
higher locomotor activity at high light intensity there was no negative effect on growth
rate and feed conversion. This is in contrast to earlier results where high light intensity was
found to reduce growth and deteriorate feed conversion rate (Proudfoot and Sefton, 1978).
Prayitino et al. (1997) reported that high intensity of red light stimulated the activity of
broilers. Boshouwers and Nicaise (1993) found that high frequency UV light produced
higher activity in laying hens as compared to low frequency UV light.
High light intensities and particular light sources show some potential to increase the
activity of chickens. Their impact on leg problems and welfare, however, has still to be
Chickens kept on continuous light (fluorescent and incandescent), continuous darkness
or under dim light developed ocular enlargement and shallow anterior chambers (Lauber
and Kinnear, 1979). The intraocular pressure was not influenced by the light treatment
(Whitley et al., 1984; Li et al., 1995). Similar results have been reported in turkey poults
by Davis et al. (1986). The continuous light effect on the chicken eye could be avoided by
providing at least 4 hours of darkness in one block at the same time of the day (Li et al.,
2000). In most studies of light on the chicken eye chicks of layer strains have been used.
Troilo et al. (1995) found significant differences in the reaction of different strains to
different light schedules. Therefore the extension of the above mentioned results on broiler
chicks must be considered with reservations.
Final conclusions
In conclusion the welfare problems of broilers are caused by factors which enable fast
early growth, such as genetic background and extended lighting programmes. Fast
growing lines under continuous light programmes decrease their locomotor activity and
increase the time spent sitting with age. Low locomotor activity in combination with high
early growth rate causes development problems in leg bones and cartilage, which result in
deformation of leg bones and gait anomalies. High duration of time spent sitting on wet
litter lead to skin lesions at the breast and legs, and contribute to deterioration of the
welfare situation. It is assumed that these leg problems are painful. It has been proved that
measures which reduce the early growth rate generally improve the welfare situation of
broilers. The use of slow growing broilers as alternative to reduce growth rate in fast
growing broilers has shown to be more efficient in reducing leg weakness and metabolic
diseases. Stocking density influences welfare criteria mainly through litter and air quality,
and its negative effects can be reduced by adequate management procedures. Moisture and
temperature of the litter increase with age of the broiler and with increasing stocking
density. This leads to thermal discomfort of the animals at the end of the growing period.
Therefore it is recommended to monitor the physical and behavioural conditions of the
birds rather than fixing data on maximum stocking density and other environmental
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... As an alternative Tallentire et al. (2018) used routinely collected data on carcass condemnation, stocking density and mortality to assess flock welfare. This allowed a comparison of large numbers of flocks, but important welfare measures such as contact dermatitis, lameness and behaviors (Bessei, 2006;EFSA, 2012) were lacking in this alternative approach. ...
... In the assessment of the different production systems, most measures that have been selected previously (de Jong, 2019) could be included because data were collected by the slaughterhouse and hatchery or (temporarily) replaced by resource-based measures. Only quality of locomotion (gait score), one of the major welfare issues in broiler chickens (Bessei, 2006;EFSA, 2010) and one of the measures of the Welfare Quality broiler assessment protocol (Welfare Quality, 2009), could not be included because of lack of routinely collected data. It is highly recommended to collect gait score data on a routine basis in commercial flocks and to include these data in flock welfare assessments, for example, by application of new technologies (Dawkins et al., 2009;Van Hertem et al., 2018). ...
... Our approach is considered as a possible method to include animal welfare in the overall sustainability assessment of broiler production systems. It includes the most important welfare issues in broiler chickens (Bessei, 2006;EFSA, 2010;2012), and it provides insight in differences between flocks with respect to the selected measures. Furthermore, such a welfare assessment method should not be considered as static but should be updated as soon as new developments in the field are available, for example, methods to assess lameness on a routine basis. ...
Full-text available
There is a trend towards broiler production systems with higher welfare requirements, that use slower growing broiler strains, apply a reduced stocking density and provide environmental enrichment. Although these separate factors each contribute to increased broiler welfare, there is little information on their combined effect on broiler welfare under commercial conditions, and on the variation in welfare performance of flocks within production systems. The aim of this study was to compare the welfare performance and the between-flock variation in welfare of three Dutch commercial broiler production systems differing in welfare requirements: Conventional (C), Dutch Retail Broiler (DRB) and Better Life one star (BLS). We applied a welfare assessment method based on the Welfare Quality® broiler assessment protocol, in which we used five animal-based welfare measures collected by slaughterhouses and hatcheries (mortality, footpad dermatitis, hock burn, breast irritation, scratches), and three resource- or management-based measures (stocking density, early feeding, environmental enrichment). Data were collected for at least 1889 flocks per production system over a 2-year period. To compare the different measures and to generate an overall flock welfare score, we calculated a score on a scale from 0-100 (bad-good) for each measure based on expert opinion. The overall flock score was the sum of the scores of the different welfare measures. The results showed that with increasing welfare requirements, a higher total welfare score was found across production systems (BLS>DRB>C; P<0.0001). Regarding individual measures, C generally had lower (worse) scores than BLS and DRB (P<0.05), except for scratches where C had highest (best) score (P<0.001). Both welfare measure scores and the total welfare score of flocks showed large variation within and overlap between systems, and the latter especially when only the animal-based measures were included in the total flock score. Total flock score ranges including animal-based measures only were: 112.1 – 488.3 for C, 113.0 - 486.9 for DRB, 151.3 – 490.0 for BLS (on a scale from 0 (bad) – 500 (good)), with median values of 330.8 for C, 370.9 for DRB, and 396.1 for BLS respectively. This indicates that factors such as farm management and day-old chick quality can have a major effect on the welfare performance of a flock and that there is room for welfare improvement in all production systems.
... These abnormalities mainly affect the bones and joints of broiler chickens (Edwards and Veltmann, 1983;Julian, 1984;Bradshaw et al., 2002;Shim et al., 2012a,b), causing problems with skeletal or structural development. Unlike other conditions causing lameness, contact dermatitis is associated with inflammation and lesions of the skin rather than disturbances in the bone structure (Bessei, 2006). In broiler chickens, contact dermatitis is commonly found on the feet or hocks, being referred to as footpad dermatitis (FPD) and hock burns (HB), respectively (Hartcher and Lum, 2020). ...
... Severe contact dermatitis can be associated with pain and increased propensity to secondary bacterial infections, which may aggravate leg disorders (Bessei, 2006;Hartcher and Lum, 2020). Even though the low locomotor activity and prolonged time spent sitting are not a welfare problem per se, they can cause or aggravate the risk of contact dermatitis, especially if the birds are raised in poor environmental conditions, with wet litter and high ammonia levels (Robins and Phillips, 2011). ...
... Despite the widespread use of the Bristol gait scoring scheme to assess lameness in commercial broiler flocks at farm and research settings, this method provides a subjective estimation of birds' walking ability and requires observers to classify the different degrees of gait problems. This can be difficult when comparing strains with vastly different phenotypes, as differences in motivation to walk (Bizeray et al., 2000;Bokkers and Koene, 2004), body conformation (Corr et al., 2003a), and temperament (Bizeray et al., 2000;Castellini et al., 2002;Bokkers and Koene, 2004;Bessei, 2006;Dixon, 2020) may influence birds' locomotion and/or gait. Therefore, other tests have been studied to assess lameness and leg health in broiler chickens. ...
Full-text available
In this study, the mobility, incidence, and severity of contact dermatitis and litter moisture content were assessed in 14 strains of broiler chickens differing in growth rate. The strains encompassed 2 conventional (CONV; ADG 0-48 >60 g/d) and 12 slower-growing (SG) strains categorized as FAST (ADG 0-62 =53-55 g/d), MOD (ADG 0-62 =50-51 g/d), and SLOW (ADG 0-62 <50 g/d), with 4 strains in each category. A total of 7,216 mixed-sex birds were equally allocated into 164 pens (44 birds/pen; 30 kg/m 2) in a randomized incomplete block design, with each strain represented in 8-12 pens over 2-3 trials. From each pen, 4-6 birds were tested in the latency-to-lie (LTL) and group obstacle tests one week prior to the birds reaching 2 target weights (TWs) of approximately 2.1 kg (TW1: 34 d for CONV and 48 d for SG strains) and 3.2 kg (TW2: 48 d for CONV and 62 d for SG strains). The incidence of footpad dermatitis (FPD) and hock burns (HB) were evaluated a day prior to each TW. Litter moisture content was determined biweekly from d 14 to d 56. At TW1, CONV and SLOW had longer LTL than FAST birds. At TW2, CONV, MOD, and FAST birds had similar LTL. At both TWs, CONV birds were lighter than FAST birds in the group obstacle test, yet their number of obstacle crossings was similar. At TW1, CONV birds had greater incidence of FPD than FAST and MOD, while at TW2, CONV birds had greater incidence than the other categories. The incidence of HB in CONV and MOD was greater than SLOW birds at TW1, while at TW2, the incidence of HB was greater in CONV and FAST birds vs. MOD and SLOW birds. Litter moisture content was high in all categories from d 28 onwards. Our results indicate that both BW and growth rate influence leg strength and walking ability, whereas the overall high litter moisture content and to a lesser extent growth rate influenced the incidence of contact dermatitis.
... Because there is a lack of fully effective strategies to improve leg health without influencing growth, there is an increasing interest in the use of slower-growing (SG) strains to decrease skeletal abnormalities and improve the walking ability and welfare of broiler chickens (Bessei, 2006;Shim et al., 2012b;Dixon, 2020). Although comparisons between a few strains of FG and SG broilers have been performed (Bokkers and Koene, 2003;Dixon, 2020;Mancinelli et al., 2020), there is a scarcity of studies that investigate different strains of broiler chickens raised under similar conditions and tested at a similar BW. ...
... The link between selection for accelerated growth and susceptibility to leg disorders in broiler chickens has been well-documented (Julian, 1998;Shim et al., 2012b;Williams et al., 2004;Dixon, 2020). Since reducing the growth rate decreases leg disorders to some extent, it has been suggested that the use of SG strains may decrease leg abnormalities that cause both welfare and economic issues in the poultry industry (Julian, 1998;Bessei, 2006;Shim et al., 2012a,b). Therefore, the aim of this study was to investigate the differences in tibial morphology, breaking strength, and composition (inorganic and organic content) as indicators of bone quality and bone measurements in 14 strains of broiler chickens (separated into 4 categories based on similarity of growth rate to TW 2) raised under similar conditions. ...
... BW. Even though skeletal disorders are multifactorial conditions, growth rate and BW are among the factors considered to play a crucial role in the incidence of leg abnormalities (Julian, 1998;Bessei, 2006;Shim et al., 2012b). In addition, bone development and morphology are affected by age (Lilburn, 1994;Talaty et al., 2009). ...
Full-text available
This study was conducted to determine the differences in bone traits in 14 strains of broiler chickens differing in growth rate. The strains encompassed 2 conventional (CONV; ADG0-48>60 g/d) and 12 slower-growing (SG) strains classified as FAST (ADG0-62=53-55 g/d), MOD (ADG0-62=50-51 g/d), and SLOW (ADG0-62<50 g/d), with 4 strains represented in each SG category. A total of 7,216 mixed-sex birds were equally allocated into 164 pens (44 birds/pen; 30 kg/m²) in a randomized incomplete block design, with each strain represented in 8-12 pens over 2-3 trials. From each pen, 4 birds (2 males and 2 females) were individually weighed and euthanized at 2 target weights (TWs) according to their time to reach approximately 2.1 kg (TW1: 34 d for CONV and 48 d for SG strains) and 3.2 kg (TW2: 48 d for CONV and 62 d for SG strains). Tibiae samples were dissected, and length and diameter were recorded. Left tibiae were used for tibial breaking strength (TBS) at both TWs and tibial ash at TW2. At TW1, CONV birds’ tibiae were narrowest and shortest (P<0.001), yet had similar TBS compared to the other categories (P>0.69). At TW2, category (P>0.50) had no effect on tibial diameter, yet CONV birds had the shortest tibiae (P<0.001). The CONV birds had greater TBS:BW ratio than FAST and MOD birds at both TWs 1 and 2 (P<0.039) and similar ash content as the other categories at TW2 (P>0.220). At 48 d of age, CONV birds had the greatest absolute TBS (P<0.003), yet lower TBS:BW ratio than SLOW birds (P<0.001). Tibiae from CONV birds were longer than MOD and SLOW birds, and thicker in diameter than the other categories, yet CONV birds had the lowest dimensions relative to BW (P<0.001) at 48 d, indicating a negative association between accelerated growth and tibial dimensions. These results indicate that differences in functional abilities among categories may be due to differences in morphometric traits rather than differences in bone strength and mineralization.
... The present study investigated the impact of raising male broilers with two divergent growth rates at two stocking densities on carcass composition and meat quality. It has been well established that high stocking densities can negatively impact broiler production performance and welfare on-farm (Shanawany, 1988;Feddes et al., 2002;Sørensen et al., 2002;Dawkins et al., 2004;Thomas et al., 2004;Dozier et al., 2005;Bessei, 2006;Buijs et al., 2009). However, limited research has compared the impact of stocking density on broiler meat yield and quality, especially on broilers from different strains. ...
... Age likely contributed to the greater slow-growing broiler frame and skin yields because they were older at processing. Slow-growing broilers have longer legs (Essary et al., 1951;Kokoszy nski et al., 2017;Weimer et al., 2020) and are more active and mobile than conventional broilers (Savory, 1975;Castellini et al., 2002;Bessei, 2006). Lewis and colleagues (1997) raised Ross and ISA 'Label Rouge' broilers at two stocking densities and found that birds stocked at 4.25 birds/m 2 had greater breast meat yield and larger frames than birds stocked at 17.0 birds/m 2 , and slow-growing broilers had greater wings and bone yields than conventional broilers. ...
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The fast growth rate of broiler chickens is a welfare concern that has increased consumer interest in chicken from slower growing (SG) broilers. Replacing conventional (CONV) broilers with SG broilers will reduce chicken supply and SG broilers require different management practices than CONV. This study evaluated the effects of 2 stocking densities on the carcass composition and meat quality of CONV broilers that reach market weight at 42 d and SG broilers that reach market weight at 63 d. Male broilers from each strain were exclusively stocked into 16 pens at a density of either 29 kg/m² or 37 kg/m². Live body, carcass without giblets (WOG), and part weights were recorded and used to calculate yield. Initial and 24-hour pH, color (L*, a*, and b*), cooking loss, and Warner Bratzler shear force of the breast and thigh muscles were measured. Birds from both strains reached similar live body and carcass weights. CONV had 3.4%, 13.0%, and 2.8% greater (P ≤ 0.002), carcass, breast, and tenderloin yields, while SG had 2.7%, 5.0%, 7.5%, and 1.2% greater (P < 0.0001) wings, leg quarters, frame, and skin yields, respectively. CONV breast 24-hour pH and cooking loss were greater (P ≤ 0.04) than SG. While SG thigh shear force was greater than CONV (P = 0.008), breast shear force was the lowest for CONV stocked at 29 kg/m² and the greatest for SG stocked at 37 kg/m² (P = 0.04). SG had a paler breast than CONV, while CONV had a yellower breast than SG (P < 0.0001). While SG had a redder thigh than CONV (P = 0.002), SG stocked at 29 kg/m² had a redder breast than SG stocked at 37 kg/m², with both CONV groups intermediate (P = 0.04). These results indicate that differences in male broiler meat quality were affected more by strain than by stocking density. Compared with CONV, SG broiler meat quality was more affected by stocking density in this study.
... Regardless of the type of stress induced in broilers, the result consists in a decrease in production and a decline in health (Caballero and Gaona at Rapid growth, feeding, management procedures have led to numerous problems regarding the welfare of broiler (Bessei, 2006). Optimal performance in terms of broiler growth rate focuses on monitoring and controlling microclimate parameters: temperature, relative humidity, ventilation, ammonia and carbon dioxide levels (Barnwell et al., 2002;Corkery et al., 2013). ...
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The research was carried out in broiler houses coming from a commercial broiler farm. Two consecutive series of broiler were followed for each of the specific housing conditions in terms of bedding quality: straw: series 1 and 2 in shelter H4 and bedding mixture: ¼ straw and the rest sawdust for series 1 and 2 housed in shelter H10. The microclimate parameters were monitored daily in three different areas, the value of the three readings representing the average. To reduce the pH of the bedding and inclusive of the removal of ammonia resulting from the degradation of organic matter in the bedding, it is returned 2-3 times a week. The results reveal that: there are no exceedances of the values in terms of physical parameters of microclimate, between them there are extremely significant correlations (positive or negative). The correlation between the temperature of the straw bedding and the carbon dioxide in the shelter air is extremely significant and insignificant at the level of the mixed bedding. The pH of the bedding has lower values in the case of the straw ¼+ sawdust mixture by turning the bedding 2-3 times a week. The temperature value at the bedding level is lower in the case of straw compared to the mixture of straw ¼+ sawdust (29.69±2.38 0 C-26.35±2.64 0 C), which entails significant differences (*P<0.05). Between the quality of the bedding in terms of pH and the amount of ammonia monitored at the level of the houses, there is an extremely close negative relationship: (-0.83 *** ppm NH3), straw bedding and (-0.96 *** ppm NH3) straw ¼+ sawdust mixture bedding. Conclusion: keeping the microclimate parameters under control by ensuring the necessary air volume, monitoring the pollutants but also the physical microclimate parameters, regular return of bedding have as a result low mortality rate and low percentage of ammonia burns which denotes ensuring good welfare conditions.
... Food systems account for 26% of global greenhouse gas (GHG) emissions, of which most (59%) comes from livestock production (including animal-sourced products, combined with the increasing human population, has led to intensified livestock farming systems (Gregory and Grandin, 2007;Harrison, 1964;Thompson, 2015). The high stocking densities typical of such systems have been linked to a series of negative welfare effects (Bessei, 2006;Dawkins et al., 2004;Peden et al., 2018), as well as dependence on antibiotics to combat increased disease prevalence and boost food conversion rates-promoting both antibiotic resistance and antibiotic spread through the environment (Kivits et al., 2018). Intensive farming practices also amplify the risk of zoonoses, such as coronaviruses (Allen et al., 2017). ...
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Livestock production systems are associated with climate change, land degradation, and animal welfare concerns, while overconsumption of animal-sourced foods is a major driver of human disease. Thus, shifting towards plant-rich diets is expected to deliver benefits for human health, the environment, and animal welfare. Nevertheless, diets high in animal products are flourishing, especially in high-income countries. Here, we take a novel inter-disciplinary approach to evaluating sustainability of diets by assessing five common plant-rich diets (Mediterranean, flexitarian/semi-vegetarian, vegan, vegetarian, and pescatarian) on two metrics. First, we established each diet's environmental, human health, and animal welfare impacts, using quantitative data sourced from a review of the literature, including life cycle assessments. Second, we evaluated the human factor by surveying current consumer dietary preferences (i.e., which diet participants had followed over the past week) and the likelihood of adopting each plant-rich diet in the future, among a sample of Australian adults (n = 253). Combining the results from the review and the survey in a Behaviour Prioritization Matrix (BPM), the Mediterranean diet was shown to have the greatest projected positive impact, followed by the vegetarian diet. This study is the first to combine assessments of sustainable diets on the three dimensions of environment, human health, and animal welfare with probability of adoption. Our findings highlight the necessity of assessing plant-rich diets through a holistic lens when identifying target diets to promote, in order to support sustainable food systems in high-income countries.
... Among the main factors for the condemnation of broiler feet are the contact lesions and keratosis. The contact lesions in the tibiotarsal region, also known as hock burn, contact dermatitis and dermatitis are characterized by the presence of blackish or brownish coloration on the skin of the chickens' tibiotarsal region (Bessei, 2006). Besides the economic losses due to discards, it also impairs the broilers performance and violates the technical recommendation of animal welfare in poultry production, because it results in pain for the bird, evidenced by the slowly locomotion or even reluctance to move (Louton et al., 2020). ...
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Brazil is considered as a great broiler feet exporter, especially for the Chinese trade. Contact lesions at the tibiotarsal region are responsible for economic losses and there is no model for its classification, thereby this study presents a fast and practical grade system to be used in the poultry industry and proposes these lesion characterizations into three different grades. For this, correlation was made between macroscopic, histological findings and microbiological quantification (Escherichia coli, Staphylococcus spp., Streptococcus spp. and sulphite-reducing clostridia) from contact lesions in the tibiotarsal region of 112 broiler carcasses, divided in four groups (n=28), accordingly to the lesion's intensity. There were no significant differences in microbiological quantification among the groups (p>0.05) except for the grade 3 group, as grade 1 and 2 lesions were in the early stages and histopathological changes such as ulceration were not observed. In grade 3 lesion group, it was observed bacterial cocci grume and ulceration at the articular region and significantly higher microbiological count (p<0.05) for E. coli and Staphylococcus spp. In conclusion, the visual standard proposed in this work, correlated and confirmed by the histopathologic, and microbiologic characterization, allows to precise and fast ascertainment of the contact lesion grade in the tibiotarsal regions of broiler carcasses. Moreover, it should be highlighted that grades 1 and 2 alterations are not caused by an inflammatory process caused by pathogenic agents and should not be considered a public health risk.
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In 2018, over nine billion chickens were slaughtered in the United States. As the demand for chickens increases, so too have concerns regarding the welfare of the chickens in these systems and the damage such practices cause to the surrounding ecosystems. To address welfare concerns, there is large-scale interest in raising chickens on pasture and switching to slower-growing, higher-welfare breeds as soon as 2024. We created a box model of US chicken demographics to characterize aggregate broiler chicken welfare and land-use consequences at the country scale for US shifts to slower-growing chickens, housing with outdoor access, and pasture management. The US produces roughly 20 million metric tons of chicken meat annually. Maintaining this level of consumption entirely with a slower-growing breed would require a 44.6%–86.8% larger population of chickens and a 19.2%–27.2% higher annual slaughter rate, relative to the current demographics of primarily ‘Ross 308’ chickens that are slaughtered at a rate of 9.25 billion per year. Generating this quantity of slower-growing breeds in conventional concentrated animal feeding operations (CAFO) would require 90 582–98 687 km ² , an increase of 19.9–30.6% over the 75 577 km ² of land used for current production of Ross 308. Housing slower-growing breeds on pasture, the more individually welfare-friendly option, would require 108 642–121 019 km ² , a 43.8–60.1% increase over current land use. Allowing slower-growing breeds occasional outdoor access is an intermediate approach that would require 90 691–98 811 km ² , an increase of 20–30.7% of the current land use, a very minor increase of land relative to managing slower-growing breeds in CAFOs. In sum, without a drastic reduction in consumption, switching to alternative breeds will lead to a substantial increase in the number of individuals killed each year, an untenable increase in land use, and a possible decrease in aggregate chicken welfare at the country-level scale. Pasture-based management requires substantial additional land use. These results demonstrate constraints and trade-offs in animal welfare, environmental conservation and food animal consumption, while highlighting opportunities for policies to mitigate impacts in an integrated manner using a One Health approach.
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The assessment of foot pad dermatitis at slaughter is a suitable method to assess and monitor the welfare of broilers. The goals of this study were to define and validate a camera-based score that could identify macroscopic lesions of the foot pads, to identify errors, and to assess possible external factors that could influence the assessment. In the first phase 200 feet of broilers and in the second phase 500 feet were collected at slaughter, assessed visually, hung back into the evisceration line, and assessed by an automatic system. The camera score cut-off values were defined in the first (= calibration) phase. In the second (= validation) phase, the performance of diagnosis for these cut-off values was evaluated, and possible errors in the assessment of reference surface area and foot pad lesions were analyzed. The results showed that, in particular, Macro Scores 0, 2, and 3 could be identified with sufficiently high sensitivity. For Macro Score 1, the sensitivity of diagnosis was not sufficiently high in the two evaluated software versions. The current automatic assessment systems at slaughter could be adjusted to the cut-off values in order to classify foot pad dermatitis lesions. Furthermore, software updates can enhance the performance measures and lower the probability of errors.
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Contact dermatitis is a lesion of the skin of broilers, which leads to a decrease in the quality of the carcass by 15-30 %. It is described as brown-black erosions and ulcers that occur on the breast (breast blisters, BB), hock burns (HB) and on the skin of the central pulp of the foot (food pad dermatitis, FPD). The most commonly affected is the pulp of the foot, followed by the hocks and chest. There are a number of factors that lead to crumb dermatitis. These include: the density of planting birds; type of troughs and the order of their use; feeding; the level of temperature and humidity in the room; type of litter, its quality and quantity; intestinal health. Birds are kept at a density of 8 individuals/m2 suffered less from dermatitis than those kept at a density of 13 individuals/m2 . Moreover, the harmful effects of high density were particularly pronounced at 18 individuals/m2 . The prevalence and severity of this pathology in broilers increases at later stages of fattening. Pododermatitis spread to several layers of skin. The condition of the crumbs worsened when the bird reached slaughter age with up to 64 % of the carcasses affected. In this case, lesions of the hocks and chest were rare. Wet litter (> 30 % moisture) is associated with an increase in the incidence and severity of contact dermatitis in broiler and turkey housing systems. This state of litter is most often registered in the winter-spring and autumn seasons. The quality of the litter, especially taking into account its humidity, has been identified as an important issue of well-being, which has a great negative impact on the condition of feathers, limb health and the frequency of contact dermatitis. Litter temperature is also important. With its growth, the degree of contact dermatitis increases. The reason for the increase in litter temperature is the increase in planting density and the accumulation of more manure, which enhances bacterial fermentation. With wet litter, bird feathers become wet or contaminated with litter, feces and dirt. It loses its protective properties. The level of bird welfare is declining sharply. Diagnosis of contact dermatitis in poultry is based on characteristic clinical signs. These are lameness, impaired mobility and discoloration of the skin, which often develops into an ulcer. The lesions are clearly separated from the intact tissue and often appear as ulcers surrounded by a deep hemorrhagic shaft. Contact dermatitis can develop in less than a week. Characteristic signs at the beginning of the disease are swelling, redness and increase in local temperature, thickening of the skin. Deep ulcers usually lead to abscesses in the underlying tissues and structures. Often the affected area is covered with crusts. If large ulcers develop, they can cause pain, slow growth, obstruct gait, and open bacteria to underlying tissues. Key words: broilers, contact dermatitis, dermatitis of the central pulp of the finger, dermatitis in the area of the hocks, dermatitis in the chest.
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A total of 3544 chicken broilers were used in an experiment in which chickens were housed at 3.72, 5.55, 7.44, and 9.27 dm2 floor area per bird. Increased bird density resulted in a significant (P<.05) linear reduction in body weight of both males and females and adversely affected carcass quality. There was a significant (P<.05) increase in the incidence of breast blisters in females with the linear effect approaching significance for males. With increased stocking density, the monetary returns per bird started, declined linearly. An opposite and significant (P<.05) effect occurred when returns were based on units of floor area.
The performance traits of broilers reared in different stocking density groups were investigated. Data were obtained from 910 broilers housed in litter-type pens at densities of 12.5 (1), 15 (2), 17.5 (3) and 20 (4) broilers/m2. Each pen had 14 m2 floor space. More than 60% of the broilers were selected by random sampling and were weighed on the 21st, 35th and 49th days of investigation. Body weight estimates of the 1, 2, 3 and 4 broilers/m2 density groups were 1634.3, 1511.7, 1506.5. and 1503.9 g respectively. Mortality rates were 6.2, 7.1, 7.7 and 6.4% for the same groups respectively. Feed efficiency values were estimated to be 1.97, 2.06, 2.07, and 2.09 kg at 49 days of age for the same groups respectively. The diffeences between the values of the groups with respect to body weight at the 35th day were not statisticaly significant. The first group had higher body weight mean estimates than the other groups at the 49th day (P<.01). On the 21st day of research, the first group had a greater body weight mean estimated than the third and fourth groups (P<.05). The differences between the mortality rate values of the groups were not statistically significant at 21. 35. and 49 days of age. Consequently, it may be said that the increase in the number of brids housed per m2 floor space in pens contributed to a more desirable mortality rate and feed conversion rate; therefore, a stocking density broilers/m2 instead of 10-12 broilers/m2 in broiler rearing has more practical benefit and is more productive.
Continuous aeration of faeces-litter mixture in broiler houses leads to a reduction of ammonia emission. In this trial the influence of continuous aeration by using a Trampoline floor in a broiler house on animal performance and carcass classification was estimated. Comparative investigations were carried out in a double-storey stable. The only difference between the two compartment of this stable was the different construction of the floor. In one storey the animals were stalled in a conventional housing system, in the other storey the stable was modified by the Trampoline floor. In both compartment chopped straw was used as litter material. The influence of the Trampoline floor on life weight, carcass weight, animal losses and carcass classification were investigated. Analysis of variance with data of six repetitions of this trial was carried out. The statistical evaluation leads to following results: Animals held on the Trampoline floor gained more weight, but also more animal losses were found in this compartment. Better carcass classification of broiler housed in the stable with continuous aeration of the faeces-litter mixture could be established.
Lame and sound broilers, selected from commercial flocks, were trained to discriminate between different coloured feeds, one of which contained carprofen. The two feeds were then offered simultaneously and the birds were allowed to select their own diet from the two feeds. In an initial study to assess the most appropriate concentration of drug, the plasma concentrations of carprofen were linearly related to the birds' dietary intake. The walking ability of lame birds was also significantly improved in a dose-dependent manner and lame birds tended to consume more analgesic than sound birds. In a second study, in which only one concentration of analgesic was used, lame birds selected significantly more drugged feed than sound birds, and that as the severity of the lameness increased, lame birds consumed a significantly higher proportion of the drugged feed.
Recently it was shown that chicken susceptible to ascitcs show increased Troponin T levels in blood. As it is believed that ascites is of the same origin as the sudden death syndrome (SDS), experiments were conducted to test the relation between the incidence of SDS and Troponin T levels in the blood of broilers. Three commercial broiler breeds and pedigreed birds of two single crosses were included in the survey. Troponin T levels were determined with the Boehringer Enzymun-Test. There was no clear relation between the observed slight difference in SDS mortality between breeds and Troponin T levels. However, the highest mortality by SDS was observed in the sire line that also showed the highest Troponin T levels. Heritability estimates (MMLSML) for native Troponin T levels were 0.201 for paternal half-sibs and 0.391 for full-sibs. Estimates for transformed values were 0.099 and 0.121, respectively. Based on maternal half-sibs, the estimates were poor. Using the animal model (REML) resulted in heritability estimates of 0.23 for transformed und untransformed Troponin T values.