Taken from the site of Animal Liberation Australia www.animalliberation.org.au/henbeak.php
Debeaking is carried out on most laying hens when they are chicks. The Code of Practice allows up to half of the upper beak and one third of the lower beak to be cut off with a hot blade. However, since the beaks of young chicks are so small, it is hard to judge accurately and sometimes more is cut off. Debeaking is done to minimise the injuries caused when hens peck each other.
Image from the site of United Poultry Concerns
The Farm Animal Welfare Council (FAWC), set up by the UK government, has described this mutilation as " a serious welfare insult to the hen " (1).
SA research scientist Dr Phil Glatz has described the pain and stress of
debeaking as follows (2):
" In the short term beak trimming is likely to be stressful in a number
of ways. The hen has to be approached, caught and restrained by the operator - a
procedure which has been shown to evoke fear in hens. The procedure of cutting
and cauterising the beak of the hen with a heated blade is likely to result in
acute short term pain because of the presence of cutaneous afferent nerves in
the beak which respond to thermal stimuli. Furthermore, the beak of hens
contains mechanoreceptors which when removed appear to impair the mechanical
ability of the beak to pick up food both in the short and long term. "
What is the evidence that debeaking is painful?
Debeaked hens lose weight and eat less for several weeks (2-4). In part, reduced food intake is due to inefficient feeding - debeaked birds have more difficulty picking up food and have to peck several times before they succeed in picking it up (3). However, if local anaesthetic is applied to the beak, debeaked birds don't eat less in the first 24 hours, so the difference is also due to pain in the beak stump (4).
When beak stumps are dissected at various times after debeaking, it is
evident that nerve endings grow back in a tangled mass called a neuroma. The
development of neuromas has been described as follows (5):
" At 10 days there was evidence of nerve regrowth with some
enlargement of the end of the nerve. This regeneration and regrowth of the
nerve fibres continued so that by 15 days clear neuroma was present at the
end of the nerve stump together with numerous bundles of regenerating
fibres. These regenerating fibres continued to grow but, because of the
adjacent scar tissue, were unable to innervate dermal structures and
consequently the fibres grew back on themselves to form a complex mass of
intertwining regenerating nerve fibres together with the surrounding tissue.
"
Abnormal discharges have been observed in these neuromas, even when the nerves are not stimulated. This has led researchers to conclude that hens suffer chronic pain in the beak stump, much like the pain suffered by many human amputees (6).
Another indication of chronic pain is that debeaked birds are less active - they spend more time dozing/resting and less time pecking/preening (7-9). Such inactivity is a common long term response to pain in animals.
These negative consequences are reduced if chicks are debeaked soon after hatching, rather than later in life. However, the birds are still less efficient at picking up food and water, show increased sensitivity in the beak stump, and still have neuromas at 28 weeks of age (10).
Dr Ian Duncan, a well-known poulty researcher, has summarised the effects of debeaking as follows:
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"There is now good morphological, neurophysiological and behavioral evidence that beak trimming leads to both acute and chronic pain. The morphological evidence is that the tip of the beak is richly innervated and has nociceptors or pain receptors. This means that cutting and heating the beak will lead to acute pain. In addition, it has been shown that as the nerve fibers in the amputated stump of the beak start to regenerate into the damaged tissue, neuromas (tumors) form. Neuromas are tiny tangled nerve masses that have been implicated in phantom limb pain (a type of chronic pain) in human beings. The neurophysiological evidence is that there are abnormal afferent nerve discharges in fibres running from the amputated stump for many weeks after beak trimming - long after the healing process has occurred. This is similar to what happens in human amputees who suffer from phantom limb pain. The behavioral evidence is that the behavior of beak-trimmed birds is radically altered for many weeks compared to that shown by sham-operated birds. In particular, classes of behavior involving the beak, namely feeding, drinking, preening and pecking at the environment,, occur much less frequently, and two behavior patterns, standing idle and dozing, occur much more frequently. The only reasonable explanation of these changes is that the birds are suffering chronic pain." Taken from the site of United Poultry Concerns |
Hens are social animals, and many social animals establish a dominance hierarchy, or pecking order. Setting up this order can involve threats and even actual aggression, but in stable social groups each hen knows her place. If a subordinate hen is threatened by a more dominant hen, she lowers her head and moves away.
When hens are crowded together in cages, or are kept in large groups where they can't recognise each other, aggression can be a major problem and can result in injuries and even deaths.
Unfortunately, as farmers have bred hens to lay more and more eggs over the years, they have also inadvertently bred more aggressive hens (11). Therefore, flocks have to be managed carefully to control aggression.
What factors increase feather pecking and aggression?
Some of the factors that have emerged from research include frustration, bright light, large group size, lack of suitable material to peck at, lack of material for dustbathing, and the strain (breed) of the hen (11).
Hens become more aggressive when they are frustrated. For example, when hungry hens could see, but not reach food, the dominant hen became more aggressive towards her subordinates (12). Therefore, any conditions which produce a sense of frustration in hens are likely to increase feather pecking.
Some researchers consider that the maximum number of birds a hen can recognise is 80 (13), while other researchers put the figure at 100 (14). In large flocks, hens can't set up a stable social order, and there is likely to be ongoing conflict with strangers. However, groups size is only one of several factors which influences aggression - feather pecking and cannibalism also occur in small groups in cages.
Feather pecking is higher when hens are kept on bare floors rather than on litter - feather pecking increases or decreases depending on which floor type the hens are moved on to (15). There is an inverse relationship between ground pecking and feather pecking, so it is essential that hens have suitable material to peck at (16-17). Similarly, feather pecking increases when hens have no material for dustbathing (18).
These findings are not surprising, since on bare floors strong instincts of the hens can find no outlet, and they are likely to feel frustration.
Some strains of hen are more aggressive than others. In one study of 3 different White Leghorn strains, there were virtually no deaths due to beak-inflicted injury in the Hy-Line W36 strain, regardless of whether they were debeaked or not. The other two strains had higher rates of injury (19).
From the previous section, three main points follow:
It is important to select a strain of bird that is less aggressive, and to
continue to breed birds that are more docile. Research has shown that
breeding for low aggression can have a marked effect in only 4 or 5
generations (20-21). Dr Mike Gentle, a well-known researcher in this area,
has concluded (22):
" In the long term, beak trimming should be phased out and
undesirable behaviour controlled by environmental means and by increased
effort being devoted to the genetic selection of commercial stocks which do
not engage in damaging pecking, either in cages or when floor-housed in
large flocks. "
Hens must be kept in groups small enough to be able to recognise each other. If they are to be kept in large sheds, the area could be subdivided into several smaller areas by even low partitions to separate one large flock into several smaller sub-groups.
Hens must be able to express their natural behaviour, including the strong urge to peck. They must have material in which to forage and dustbathe.
Good husbandry is a major factor in reducing aggression, especially preventing conditions that cause frustration or fearfulness in hens. Thus, in addition to the above, they must also have an adequate and well-balanced diet, easy access to food and water, enough space, and minimum disturbance.
Farmers need to make a much greater effort to control aggression without debeaking. It is completely unacceptable to "solve" a behavioural problem by cutting off part of an animal's body.
Farm Animal Welfare Council (1991), Report on the Welfare of Hens in Colony Systems , Surrey UK
Glatz P (1987), "Effects of beak trimming and restraint on heart rate, food intake, body weight and egg production in hens", British Poultry Science , vol 28 (601-611)
Gentle M, Hughes B & Hubrecht R, (1982) "The effect of beak trimming on food intake, feeding behaviour and body weight in adult hens", Applied Animal Ethology , vol 8 (147-159)
Glatz P, Murphy L & Preston A (1992), "Analgesic therapy of beak-trimmed chickens", Australian Veterinary Journal , vol 69 (18)
Breward J & Gentle M (1985), "Neuroma formation and abnormal afferent nerve discharges after partial beak amputation (beak trimming) in poultry", Experientia ,vol 41 (1132-1134)
Gentle M (1986), "Beak trimming in poultry", World's Poultry Science Journal , vol 42 (268-275)
Lee H-Y & Craig J (1990), "Beak trimming effects on the behavioiur and weight gain of floor-reared, egg-strain pullets from three genetic stocks during the rearing period", Poultry Science , vol 69 (568-575)
Lee H-Y & Craig J (1991), "Beak trimming effects on behaviour patterns, fearfulness, feathering and mortality among three stocks of White Leghorn pullets in cages or floor pens", Poultry Science , vol 70 (211-221)
Duncan I, Slee G, Seawright G & Breward J (1989), "Behavioural consequences of partial beak amputation (beak trimming) in poultry", British Poultry Science ,vol 30 (379-388)
Glatz P (1998), "Welfare evaluation of beak trimming", Milne's Poultry Digest , April (34,37)
Hughes B & Duncan I (1972), "The influence of strain and environmental factors upon feather pecking and cannibalism in fowls", British Poultry Science , vol 13 525-547)
Duncan I & Wood-Gush (1972), "Thwarting of feeding behaviour in the domestic fowl", Animal Behaviour , vol 20 (444-451)
Appleby M & Hughes B (1991), "Welfare of laying hens in cages and alternative systems: environmental, physical and behavioural aspects", World's Poultry Science Journal , vol 47 (109-128)
Scientific Veterinary Committee, Animal Welfare Section of the CEC (1992), On the welfare of laying hens kept in different production systems , Report
Blokhuis H & Arkes J (1984), "Some observations on the development of feather pecking in poultry", Applied Animal Behaviour Science , vol 12 (145-157)
Blokhuis H (1986), "Feather pecking in poultry: its relation with ground-pecking", Applied Animal Behaviour Science , vol 16 (63-67)
Blokhuis H (1989), "The effect of a sudden change in floor type on pecking behaviour in chicks", Applied Animal Behaviour Science , vol 22 (65-73)
Vestergaard K, Kruijt J & Hogan J (1993), "Feather pecking and chronic fear in geroups of red jungle fowl: their relation to dustbathing, rearing environment and social status", Animal Behaviour , vol 45 (1127-1140)
Craig J (1992), "Beak trimming benefits vary among egg-strain pullets of different genetic stocks", Poultry Science , vol 71 (2007-2013)
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Gentle (1998), "Genetics the ultimate answer to beak trimming", Milne's Poultry Digest , April (36-37)