Feather pecking
Encyclopedia
Feather pecking is a behavioural problem that occurs most frequently amongst domestic hens
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

 reared for egg production, although it does occur in other poultry
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...

 such as pheasant
Pheasant
Pheasants refer to some members of the Phasianinae subfamily of Phasianidae in the order Galliformes.Pheasants are characterised by strong sexual dimorphism, males being highly ornate with bright colours and adornments such as wattles and long tails. Males are usually larger than females and have...

s, turkeys, ducks and is sometimes seen in farmed ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...

es. Feather pecking occurs when one bird repeatedly pecks at the feathers of another. Two levels of severity are recognised, gentle and severe. Gentle feather pecking is considered to be normal investigatory behaviour where the feathers of the recipient are hardly disturbed and therefore does not represent a problem. In severe feather pecking, however, the feathers of the recipient are grasped, pulled at and sometimes removed. This is painful for the receiving bird and can lead to trauma of the skin or bleeding, which in turn can lead to cannibalism and death.

Feather pecking is one of the major problems facing the egg industry in non-cage
systems and is set to become an even greater issue with the EU legislation (Council Directive 1999/74/EC)http://www.eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1999:203:0053:0057:EN:PDF ban on the keeping of laying hens in barren battery cages which comes into force in 2012, and the prospect of a ban on beak-trimming (see below). Reducing feather pecking without resorting to beak-trimming is an important goal for the poultry industry.

Motivational Basis

Feather pecking is considered to be re-directed behaviour, developing either from ground pecking or pecking during dustbathing, although the former hypothesis is now the more favoured. Captive birds are very often kept in barren environments with limited foraging opportunities and in addition, are usually fed a nutrient-dense diet which can be eaten in a few minutes rather than the hours it would require to acquire during normal foraging. In combination, these cause the birds' foraging activity to be re-directed to the feathers of their conspecifics
Conspecificity
Conspecificity is a concept in biology. Two or more individual organisms, populations, or taxa are conspecific if they belong to the same species....

.
  • Feather pecking is not aggression. During aggressive encounters, hens peck exclusively at the top of the head or the comb, whereas during feather pecking, the areas of the body that are usually targeted are the base of the tail over the uropygial
    Uropygial gland
    The uropygial gland, informally known as the preen gland, is a gland found in the large majority of birds that secretes an oil that birds use for preening. The chief compounds of preen oil are diester waxes called uropygiols....

     or preen gland, the back, the tail feathers and the wing feathers.
  • Although feather pecking activity may be related to dominance relationships or the pecking order
    Pecking order
    Pecking order or just peck order is the colloquial term for a hierarchical system of social organization in chickens. It was first described from the behaviour of poultry by Thorleif Schjelderup-Ebbe in 1921 under the German terms Hackordnung or Hackliste' ...

    , formation of the dominance hierarchy is not involved in the causation of feather pecking.
  • Feather pecking is also distinct from another psychopathological
    Animal psychopathology
    Animal psychopathology is the study of mental or behavioral disorders in non-human animals.Historically, there has been an anthropocentric tendency to emphasize the study of animal psychopathologies as models for human mental illnesses...

     behaviour called feather-plucking
    Feather-plucking
    Feather-plucking, sometimes termed feather-picking, feather damaging behaviour or pterotillomania, is a maladaptive, behavioural disorder commonly seen in captive birds which chew, bite or pluck their own feathers with their beak, resulting in damage to the feathers and occasionally the skin...

     or feather-picking. In feather-plucking, birds, often housed in isolation, remove feathers from their own body; in feather pecking, however, birds peck at each other's feathers.


Sometimes, feathers that are removed are then eaten, in which case the behaviour is termed "feather eating". Whilst there may be a positive association between feather pecking and eating, at least in the individual bird, this is likely due to an overall higher pecking motivation. Eating feathers increases gut transit indicating that feather pecking and feather eating have a different motivational basis.

Development

Early experience can influence severe feather pecking in later life. Commercial egg-laying hens have often already begun feather pecking when they are transferred to the egg laying farm from the rearing farm at approximately 16–20 weeks of age, and plumage quality can then rapidly deteriorate until peak lay at approximately 25 weeks of age. Severe feather pecking can either begin or persist beyond this age although it rarely begins after 40 weeks of age.

Although there are links between gentle feather pecking and severe feather pecking, it is still not clear whether the gentle form leads to the severe form.

Some areas of the body are targeted for feather pecking and there is a pattern in the development of which areas are pecked. The rump area over the uropygial gland
Uropygial gland
The uropygial gland, informally known as the preen gland, is a gland found in the large majority of birds that secretes an oil that birds use for preening. The chief compounds of preen oil are diester waxes called uropygiols....

 and the tail are often the first body regions to show signs of plumage damage due to feather pecking, followed by the neck, wings and back, although it should be noted that in the ostrich which has a similar pattern of feather pecking development, the uropygial gland is absent.

Prevalence

Although feather pecking occurs in all commercial housing systems used for egg laying hens, it is often more prevalent or severe in loose flock systems because it is less easy to control and can spread more rapidly. Prevalence figures range between 57 to 86% of free-range flocks and 99% of hens within a flock can be affected. The UK national flock of egg laying hens is currently (2011) approximately 33 million birds of which approximately 10 million are free-range. This indicates that 5.5 million free-range hens/year are likely to be affected by feather pecking. It has been estimated that 4% of hens on free-range farms die because of feather pecking, representing 220,000 deaths each year in the UK alone due to this behavioural problem. EU legislation (Council Directive 1999/74/EC)http://www.eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1999:203:0053:0057:EN:PDF will ban battery or conventional
Battery cage
In poultry farming, battery cages are an industrial agricultural confinement system used primarily for egg-laying hens...

 cages in 2012 meaning that many producers will change to using free-range systems, possibly exacerbating this welfare problem until we learn effective methods of its control - see Defra's "A Guide To The Practical Management of Feather Pecking & Cannibalism in Free Range Laying Hens" http://www.defra.gov.uk/foodfarm/farmanimal/welfare/documents/featherpecking.pdf

Risk Factors

Feather pecking is a multifactorial problem and a large number of risk factors have been identified for commercial flocks.

Factors likely to reduce feather pecking are -

Diet

  • Minimal number of diet changes.
  • Ad libitum
    Ad libitum
    Ad libitum is Latin for "at one's pleasure"; it is often shortened to "ad lib" or "ad-lib"...

     feeding.
  • Mashed feed rather than pelleted
    Compound feed
    Compound feeds are feedstuffs that are blended from various raw materials and additives. These blends are formulated according to the specific requirements of the target animal...

    .
  • Diet balanced for protein
    Protein
    Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

     and methionine
    Methionine
    Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...

    .
  • Dietary Tryptophan
    Tryptophan
    Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...

    .

Genetics

  • White breeds such as the Amberlink
    Dekalb Amberlink
    The Dekalb Amberlink is a very popular chicken for free range, cruelty free, alternative production methods. She is very adaptive to non-cage operation, forages well, and has excellent feather retention. The feather retention being one of her best features for free range farms and other...

     compared to pigmented breeds.
  • Less flighty breeds.

Housing & Husbandry

  • Dark brooders.
  • Purchasing the hens at an earlier age and allowing them on the range earlier.
  • Delaying the onset of lay.
  • Maintaining a uniform flock (purchase single flocks and do not mix).
  • Pan feeders rather than chain feeders.
  • Nipple drinkers rather than bell drinkers.
  • Good litter quality.
  • Good air quality (low levels of ammonia and carbon dioxide).
  • Low light and noise levels.
  • House temperature above 20°C.
  • Multiple persons inspecting the hens.
  • Minimal light changes for inspection.
  • Avoiding using lights in nest boxes.

Hen behaviour

  • Increased use of the range (e.g. smaller flocks, increasing shelter, cockerels).
  • Reduced fearfulness.

Beak-trimming

Beak-trimming
Debeaking
Debeaking, also called beak-trimming is the partial removal of the beak of poultry, especially layer hens and turkeys although it may also be performed on quail and ducks. Most commonly, the beak is shortened permanently, although regrowth can occur. The trimmed lower beak is somewhat longer than...

, sometimes misleadingly termed debeaking
Debeaking
Debeaking, also called beak-trimming is the partial removal of the beak of poultry, especially layer hens and turkeys although it may also be performed on quail and ducks. Most commonly, the beak is shortened permanently, although regrowth can occur. The trimmed lower beak is somewhat longer than...

, is perhaps most accurately described as ‘partial beak-amputation’. It is performed on poultry to reduce the incidence or damage caused by feather pecking or cannibalism and involves amputating the distal one to two thirds of the bird’s beak by either a blade or infra-red beam. Beak-trimming causes welfare concerns because the internal tissue of the beak contains many nerves which are transected during the process - it is only the surface and extreme tip of the beak that is keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

ised, dead tissue. This can lead to neuroma
Neuroma
A neuroma is a growth or tumor of nerve tissue. Just as the Latin word for swelling is now restricted to neoplasias, the equivalent Greek suffix -oma has shared in that fate. Thus, the typical modern usage of neuroma is for nerve tumors...

s (abnormal nerve regeneration) developing in the amputated beak stump from which there might be abnormal spontaneous neural discharges similar to the discharges originating from stump neuromas in human amputees and implicated in phantom limb pain
Phantom pain
Phantom pain sensations are described as perceptions that an individual experiences relating to a limb or an organ that is not physically part of the body. Limb loss is a result of either removal by amputation or congenital limb deficiency . However, phantom limb sensations can also occur following...

.

It has been shown that domestic hens
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

 have iron mineral deposits in the dendrites in the upper beak and are capable of magnetoreception
Magnetoception
Magnetoception is the ability to detect a magnetic field to perceive direction, altitude or location. This sense plays a role in the navigational abilities of several animal species and has been postulated as a method for animals to develop regional maps.Magnetoception is most commonly observed in...

. Because hens use directional information from the magnetic field of the earth to orient in relatively small areas, this raises the possibility that beak-trimming impairs the ability of hens to orient in extensive systems, or move in and out of buildings in free-range systems.

A further negative aspect of beak-trimming is that it leaves birds less able to groom themselves effectively, thus beak-trimmed hens have greater ectoparasite burdens than hens with intact beaks.

Light manipulations

A widely used method of reducing feather pecking is to reduce light intensity, but because a minimum of 5 lux is necessary to maintain egg laying, intensities of 10 lux or more are recommended. At these low intensities it becomes difficult for humans to inspect the hens properly, especially in the more crowded densely populated housing systems, and human colour vision is hindered making the detection of blood almost impossible. Low light intensites may be associated with other welfare costs to the hens as they prefer to eat in brightly lit environments and prefer brightly lit areas for active behaviour but dim (<10 lux) for inactive behaviour. Dimming the lights can also cause problems when the intensity is then abruptly increased temporarily to inspect the hens; this has been associated as a risk factor of increased feather pecking and the birds can become frightened resulting in panic-type ("hysteria") reactions which can increase the risk of injury. In turkeys, low light intensities (perhaps in combination with long light phases) can cause retinal detachment and buphthalmia, a distortion of the eye morphology that can lead to blindness. This does not appear to have been investigated for layer hens under modern lighting patterns. Gradual changes in light intensity simulating a dawn and dusk at the beginning and end of the light phase rather than switching off lights abruptly enables birds to feed in anticipation of the dark period and to move safely to roosts, rather than moving in the dark and risking injury which is possibly more important in furnished systems.

It has been suggested that the absence of UV from artificial light sources may have a role in the causation of feather pecking in turkeys. The extent to which the absence of UV from artificial lights compromises poultry and other animal welfare is not yet known. Other poultry species prefer areas illuminated with additional UV, but poultry reared without UV show little indication of being stressed.

Selective breeding & Genetics

Feather pecking has a heritable component with heritabilities
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...

 for this trait ranging from 0.07 to 0.56. Lines of hens exhibiting high or low feather pecking activity have been developed by artificial selection
Artificial selection
Artificial selection describes intentional breeding for certain traits, or combination of traits. The term was utilized by Charles Darwin in contrast to natural selection, in which the differential reproduction of organisms with certain traits is attributed to improved survival or reproductive...

 with high feather pecking birds showing more feather pecking than low feather pecking birds from the second generation onwards.

Selection for indirect indicators of feather pecking, specifically intact feather cover and livability in multi-bird groups leads, has led to reductions in feather pecking and cannibalism. Considerable additive genetic variation exists for these traits with estimates of heritability
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...

 ranging from 0.22 to 0.54. A trait has been identified which combines feather pecking and cannibalism leading to severe injury or death in beak-intact birds; this has a high heritability at 0.65.

There has been less work at the molecular level of the genetics of feather pecking. Major genes for feather pecking have been found along with the polygene
Polygene
A polygene, multiple factor, multiple gene inheritance, or quantitative gene is a group of non-allelic genes that together influence a phenotypic trait. The loci or identities of the non-allelic genes are often unknown to biologist...

s. There are markers for severe feather pecking on chromosomes 1, 2, and 10 and also possibly on chromosome 3.

Devices (Bits & Spectacles)

'Devices' have been developed to reduce or eliminate the damaging effects of feather pecking. These devices require time and skill to fit and therefore have problems of practicality given the several thousands of birds usually within commercial flocks. Because of this, they are not used widely in modern poultry production
Poultry farming
Poultry farming is the raising of domesticated birds such as chickens, turkeys, ducks, and geese, for the purpose of farming meat or eggs for food. According to the Worldwatch Institute, 74 percent of the world's poultry meat, and 68 percent of eggs are produced in ways that are described as...

, except for gamekeeping
Gamekeeper
A gamekeeper is a person who manages an area of countryside to make sure there is enough game for shooting, or fish for angling, and who actively manages areas of woodland, moorland, waterway or farmland for the benefit of game birds, deer, fish and wildlife in general.Typically, a gamekeeper is...

.
  • Bits or bumpabits http://www.nationalband.com/nbtgame.htm are small, plastic circlips, the body of which passes between the maxilla and mandible of the beak
    Beak
    The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...

     and is held in place by the ends of the circlip being placed in the nostrils or nares
    Beak
    The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...

    . This device makes it difficult for the bird to completely close its beak and grasp the feathers of another individual.

  • Spectacles or 'blinders'http://www.nationalband.com/nbtgame.htm are pieces of moulded plastic, shaped to block the bird's vision and held in place again by circlips which enter the nares. These devices are based on the principle that by interfering with the vision of the bird, it is less able to visually locate the feathers of another bird and is therefore less able to grasp and pull the feathers.

See also

  • Abnormal behaviour of birds in captivity
    Abnormal behaviour of birds in captivity
    -Abnormal behaviour :When housed under captive or commercial conditions, birds often show a range of abnormal behaviours. These are often self-injurious or harmful to other individuals, and include:*Feather pecking*Cannibalism*Vent pecking...

  • Vent pecking
    Vent pecking
    Vent pecking is an abnormal behaviour of birds performed primarily by commercial egg-laying hens. It is characterised by pecking damage to the cloaca, the surrounding skin and underlying tissue...

  • Cannibalism
    Cannibalism
    Cannibalism is the act or practice of humans eating the flesh of other human beings. It is also called anthropophagy...

  • Toe pecking
    Toe pecking
    Toe pecking is a relatively rare abnormal behaviour of birds in captivity. It involves one bird pecking the toes of another and has been reported in hens and ostriches...

  • Chicken
    Chicken
    The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

  • Poultry farming
    Poultry farming
    Poultry farming is the raising of domesticated birds such as chickens, turkeys, ducks, and geese, for the purpose of farming meat or eggs for food. According to the Worldwatch Institute, 74 percent of the world's poultry meat, and 68 percent of eggs are produced in ways that are described as...

  • Battery cages
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