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Issues
- Large numbers of Individuals (860 million broilers + breedrs) and 30 million laying hens
- genetic selection= inherent problems
- low individual value= less care/vigilance per animal, financial implications
- limited public awareness/concern
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Laying hen problems
- feather pecking and cannibalism
- bone fracture
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broiler problems
- food restriction in breeders
- broiler welfare- media and public response
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Feather pecking
- def: damaging bird to bird pecking observed in laying hens, turkeys, pheasants, quail and ducks
- reports as early as 1930's
- major welfare and economic problem in the egg industry
- highly unpredictable (half of britis producers suffered outbreaks in their last flock)
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Feather pecking is NON-aggressive!
- vigourous or gental pecks:
- deliberate, repeated persistently, aimed at any part of body, recipient may withdraw, only vigourous pecks damaging
- gentle pecks more common
- allopreening?- birds being feather pecked do not resist or object
- feather pulls:
- removed feathers eaten, bare skin pathes result
- evidence for pain when feathers are removed
- reduced insulation- increased energy requirements
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Aggressive pecking
- maintenance of dominance hierarchy (different motivation)
- rarer than non-aggressive pecks (overt, rapid, forceful, rarely repeated, aimed at head or neck, recipient withdraws, damaging)
- relationship between dominance and feather pecking unclear
- confusingly, industry uses term "agression" for feather pecking
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Cannibalism
- tissue pecking aimed at skin, preen gland, or vent and underlying tissues
- correlated w/ severe feather pecking (non-aggressive)
- usually results in death (mortality up to 30% intact beak flocks)
- unpredictable
- may be triggered by accidental injury or bleeding feathers
- vent pecking associated w/ onset of lay?
- nutrient deficit? (protein level, source?, specific nutrients?)
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Beak trimming ('debeaking')
- removes part of upper beak (hot blade, infra red methods)
- causes acute pain (beak guarding)
- reduces effectiveness of beak (changes beak shape, loss of senosry feedback, beak used less forcefully (chronic pain?))
- majority of layer flocks beak trimmed
- (organic and rare breeds are not!)
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Why do chickens feather peck?
- not fully understood despite 50 years of research- unpredictability a problem
- scientific research- commercial egg production (massive differences in scale)
- mulifactorial (external factors- environmental), (internal factos-independent or environment)
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Causation: external factors (feather picking)
- light:
- damaging pecking increases w/ increasing light intensity- probably acts by increasing activity levels
- light wavelength/type also affects incidence
- floor substrate:
- evidence that feather pecking/cannibalism is redirected ground pecking/foraging
- (less feather pecking when foraging increases, fewer pecking problems when pecking substrate is provided)
- Stocking density/group size:
- evidence for size-stocking density interaction- group size affects number of peckers and potential victims
- individual recognition in large groups- breakdown of dominance hierarchy
- diet:
- studies have implicated dietary fibre, various aa, sodium, protein level
- food form effect- more pecking w/ pellets than w/ mash- layer flocks routinely fed mash
- food delivery- scatter feeding encourages foraging
- environmental enrichment- various objects and "toys" have been tested as anti-pecking devices
- limited evidence that EE reduces damaging pecking
- production system:
- various environmental factors acting together
- increased pecking problems w/ extensive systems (large group sizes, high stocking density, few peckers can inflich much damage)
- cages contain pecking problems- peckers have access to fewer birds
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Causation: internal factors
- genetic variation:
- obvious strain differences in incidence and extent of pecking damage
- individual variation: peckers and non-peckers
- some behavioural correlates demonstrated (peckers more active, peckees preen more, peckers foage less)
- cant' we select for non-peckers?
- co-selection w/ increased egg production- high egg number early onset of lay
- easier to select for pecking than against it
- limited success
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Current situation (legal)
- EU conentional cage ban in 2012
- enriched cages permitted (studies ongoing to examine effects on incidence of feather pecking)
- will laying hen welfare be improved? (directive will encourage the use of non-cage systems, pecking and dz problems likely to worsen)
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Bone biology in laying hens
- bone types:
- cortical bone, trabecular bone, medullary bone
- mineral supply function (calcium)
- supports egg shell production
- wild-birds- season formation of medullary bone
- laying hens:
- selection for early egg production and high egg yield
- sustained egg production (all year- uses all medullary bone)
- progressive loss of structural bone leading to fragility (osteoporosis)
- switch to medullary bone producition, inactivity in caged birds
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Incidence of Fracture
- 1) old fractures: occurs during the lifetime of the bird while in the production system
- 2) new fracture: occurs at depopulation due to handline
- studes examining old fractures:
- percher 25%, free range 12%, cage 5% (1990)
- Perchery 73% (2003)
- loose housed 50-78% (2004)
- cage 35% (2004)
- *most affected bones are keel (90%) and furculum
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What causes bone fracture?
- osteoporosis doesn't account for incidence
- all laying hens suffer from some degree of osteoporosis
- more fx in loose systems, especially w/ percehs
- despite positive effects of exercise on bone strength
- pressure while sitting on perch?- 59% of body weight borne by keel- cracks
- collision w/ perches/furniture?- body weight relative to wing area has changed in modern layer strains- reduced flight performance, percehes may be badly positioned- too far apart, steep angles
- mechanics of flying?- twisting forces on keel in flight?
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Current situation (bone fx)
- bone Fx likely to be painful!
- no published descritption of pain related behaviour following bone fracture- research needed
- old breaks most common- chronic pain?
- hens unlikely to be able to mobilise calsium to properly heal fx- research needed
- EU conventional cage ban 2012?- wider use of loose housing systems
- solutions?- rearing w/ perches for practice, selection for flight ability, selection for bone strength
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Broiler Production food restriciton
- Birds reared for meat= 2.5 kg in 42 days
- selection for: rapid growth, food conversion efficiency, breast meat yield, appetite, inactivity
- same genetic line
- (parents) feed intake controlled:
- slows growth
- improves health
- protects fertility
- saves money
- birds reach sexual maturity
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Food restriction
- severe- birds get ~30% of ad lib intake during rearing
- birds cont. hungry: highly active, highly motivated to feed at all times (operant feeding tests showed that motivation to eat is 3 tims greater than that of unrestricted birds subjected to 72 h food deptrivation)
- exhibit oral stereotypies related to frustration of feeding motivation (spot pecking at non-food objects, polydipsia- over drinking)
- commercial food restriction contravenes " freedom from hunger and thirst"
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how much hunger is acceptable? can we meausre hunger?
- % of ad lib intake
- behaviour- food searching, activity
- plasma glucose/non-esterified fatty acids
- plasma corticosterone
- feed of feeding (limited by crop)
- compensatory feed intake
- operant techniques (measure motiviaton)
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Types of food restriciton
- quantitative: provide less of high quality food
- qualitative: provide more food w/ lower energy content (high proportion of indigestible fibre in food)
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does qualitative restriction improve welfare?
- some evidence for benefits (increased satiety, reduced stereotypic behaviour)
- more difficult to control growth rate
- feeding motivation and activity level related to growth rate suppresion (regardless of how achieved)
- qualitative restriction has only limited scope to improve broiler breeder welfare
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What else can be done about feed restriction?
- scatter feeding (increases feeding time- foraging in litter, reduces competition- better weight uniformity)
- environmental enrichment (encourages non-destructive pecking, reduces drinking and improves litter quality)
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Current situation (restricted feed)
- accepted that food restriction of broiler breeders is a major welfare insult
- aggree that some degree of restriciton is necessary to preserve health and reproductive fitness
- feather pecking and cannibalism becoming problematic- beak trimming now utilised
- use of slower growing birds is the best solution
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Broiler welfare issues
- Celebrity chefs get involved (chicken run, anf jamies fowl dinners)
- leg disorders leading to lameness (recent survey reported over 27.6% of birds showed poor locomotion and 3.3% were almost unable to walk
- pain as well as hunger and thirst through lack of mobility
- cardiovascular problems
- foot and hock lesions
- behavioural restrictions (fitness, lameness, high stocking densities, barren environment)
- hunger in broiler breeders
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mechanisms of change
- consumer driven (media, pricing, ethical views)
- retailer driven (profit, image)
- producer driven (quality assurance, image)
- government driven (legistaltion- including EU)
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Do broilers have natural behaviour?
- release experiemtns suggest that behaviourally, domesticated animals have not lsot the ability or motivation to perform the begavioural repertoire of wild ancestors
- but are broilers more than just domesticated?
- body conformational change
- still chicks at slaughter
- rapid growth rate associated w/ all other problems
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the real welfare issue (rapid growth is associated w/...)
- cardiovascular problems and poor fitness
- leg problems
- foot and hock lesions
- reduced ability to thermoregulate
- muscle damage
- greater hunger in breeders
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Free range- solution?
- more nautral
- behavioural freedom
- environmental enrichment
- slower growth (not possible for broiler)
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problems with free range
- increase dz risk!
- in large flocks evidence that not all birds go outside
- outside space may be unsuitable (exposed, cold)
- increased foot problems
- parasites
- hygene
- predation
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intermediate solution???
- freedom foods:
- slower growing birds
- lower stocking density
- environmental enrichment
- good dz control
- lowest incidence of FPD
- smaller price increase
- more feasible
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