Vent pecking
Encyclopedia
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. Vent pecking frequently occurs immediately after an egg has been laid when the cloaca often remains partly everted exposing the mucosa, red from the physical trauma of oviposition
or bleeding if the tissue is torn by her laying an over-sized egg. Vent pecking clearly causes pain and distress to the bird being pecked. Tearing of the skin increases suceptibility to disease and may become cannibalistic leading to evisceration
of the pecked bird and ultimately, death.
were different types of cannibalism (65.51%), with vent cannibalism (38.57%) the most common. The type of housing system markedly affects the prevalence of vent pecking with 22.5% of hens affected in free-range systems, 10.0% in barn systems, 6.2% in conventional cages and 1.6% in furnished cages, with a similar rank for the severity of vent pecking injuries.
Risk factors that have been identified as increasing vent pecking include dim lights placed in nest boxes to encourage hens to use the boxes, the diet being changed more than three times during the egg laying period, the use of bell drinkers, and the hens beginning to lay earlier than 20 weeks of age. Vent pecking is associated with indicators of stress, e.g. fluctuating asymmetry
, heterophil to lymphocyte
ratio, and tonic immobility
duration. Vent pecking can be related to disease or immune challenge as it sometimes becomes prevalent in cases of Gumboro disease (Infectious Bursal Disease
) and is increased by challenges with the protein antigen, human serum albumin
(HuSA). Housing design can influence vent pecking. Mortality caused by cannibalism was reduced when hens had sufficient room to perch all facing the feed trough, thus giving their perch-mates little opportunity to peck at the vent region and increased pecking activity and cannibalistic behaviour can occur due to inadequate height of the perches. Larger group sizes lead to increases vent pecking suggesting that social learning
plays a role.
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...
of birds performed primarily by commercial egg-laying hens. It is characterised by pecking damage to the cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
, the surrounding skin and underlying tissue. Vent pecking frequently occurs immediately after an egg has been laid when the cloaca often remains partly everted exposing the mucosa, red from the physical trauma of oviposition
Oviposition
Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....
or bleeding if the tissue is torn by her laying an over-sized egg. Vent pecking clearly causes pain and distress to the bird being pecked. Tearing of the skin increases suceptibility to disease and may become cannibalistic leading to evisceration
Evisceration
An evisceration is the removal of the eye's contents, leaving the scleral shell and extraocular muscles intact. The procedure is usually performed to reduce pain or improve cosmesis in a blind eye, as in cases of endophthalmitis unresponsive to antibiotics...
of the pecked bird and ultimately, death.
Prevalence and Severity
Surveys have shown that 27% of farmers reported seeing damage to the vents of their hens and 36.9% of farmers reported vent pecking had occurred in their previous flock. Whilst farmers attributed 1.3% of mortalities as due to vent pecking the most common findings at autopsyAutopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
were different types of cannibalism (65.51%), with vent cannibalism (38.57%) the most common. The type of housing system markedly affects the prevalence of vent pecking with 22.5% of hens affected in free-range systems, 10.0% in barn systems, 6.2% in conventional cages and 1.6% in furnished cages, with a similar rank for the severity of vent pecking injuries.
Causation
The causes and development of vent pecking are multifarious.Risk factors that have been identified as increasing vent pecking include dim lights placed in nest boxes to encourage hens to use the boxes, the diet being changed more than three times during the egg laying period, the use of bell drinkers, and the hens beginning to lay earlier than 20 weeks of age. Vent pecking is associated with indicators of stress, e.g. fluctuating asymmetry
Fluctuating asymmetry
Fluctuating asymmetry is an organism’s deviation from bilateral symmetry. It can be measured in the body—as in bilateral symmetry of finger lengths—or in a particular organ...
, heterophil to lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
ratio, and tonic immobility
Tonic immobility
Apparent death, colloquially known as playing dead or playing possum, is an antipredator behavior observed in a wide range of animals in which they take on the appearance of being dead to an observer...
duration. Vent pecking can be related to disease or immune challenge as it sometimes becomes prevalent in cases of Gumboro disease (Infectious Bursal Disease
Infectious Bursal Disease
Infectious bursal disease is a highly contagious disease of young chickens caused by infectious bursal disease virus , characterized by immunosuppression and mortality generally at 3 to 6 weeks of age. The disease was first discovered in Gumboro, Delaware in 1962...
) and is increased by challenges with the protein antigen, human serum albumin
Human serum albumin
Human serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin constitutes about half of the blood serum protein...
(HuSA). Housing design can influence vent pecking. Mortality caused by cannibalism was reduced when hens had sufficient room to perch all facing the feed trough, thus giving their perch-mates little opportunity to peck at the vent region and increased pecking activity and cannibalistic behaviour can occur due to inadequate height of the perches. Larger group sizes lead to increases vent pecking suggesting that social learning
Social learning
Social learning may refer to:* Observational learning , learning that occurs as a function of observing, retaining and replicating behavior observed in ones environment or other people....
plays a role.
See also
- Abnormal behaviour of birds in captivityAbnormal 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...
- Feather peckingFeather peckingFeather pecking is a behavioural problem that occurs most frequently amongst domestic hens reared for egg production, although it does occur in other poultry such as pheasants, turkeys, ducks and is sometimes seen in farmed ostriches. Feather pecking occurs when one bird repeatedly pecks at the...
- Cannibalism (poultry)Cannibalism (poultry)Cannibalism is a behavioural problem that occurs most frequently amongst domestic hens reared for egg production, although it can also occur amongst domestic turkeys, pheasants reared as gamebirds, and other poultry species. Cannibalism occurs when one bird pecks at the skin of another and devours...
- Toe peckingToe peckingToe 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...
- ChickenChickenThe 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 farmingPoultry farmingPoultry 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