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Vent pecking is an
abnormal behaviour Abnormality (or dysfunctional behavior) is a behavioral characteristic assigned to those with conditions that are regarded as rare or dysfunctional. Behavior is considered to be abnormal when it is atypical or out of the ordinary, consists of un ...
of birds performed primarily by commercial egg-laying hens. It is characterised by
pecking Pecking is the action of a bird using their beak to search for food or otherwise investigate an object or area by tapping it. Pecking can also be used by a bird to attack or fight another bird. Pecking is frequently observed in chickens and oth ...
damage to the
cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, ...
, the surrounding skin and underlying tissue.Sherwin, C.M., (2010). The welfare and ethical assessment of housing for egg production. In ''The Welfare of Domestic Fowl and Other Captive Birds'', I.J.H. Duncan and P. Hawkins (eds), Springer, pp. 237-258 Vent pecking frequently occurs immediately after an egg has been laid when the cloaca often remains partly everted exposing the
mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...
,Potzsch, C.J., Lewis, K., Nicol, C.J. and Green, L.E., (2001). A cross-sectional study of the prevalence of vent pecking in laying hens in alternative systems and its associations with feather pecking, management and disease. Applied Animal Behaviour Science, 74: 259-272 red from the physical trauma of
oviposition The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
or bleeding if the tissue is torn by her laying an egg. Vent pecking clearly causes pain and distress to the bird being pecked. Tearing of the skin increases susceptibility to disease and may lead to
cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...
, with possible
evisceration Evisceration (pronunciation: /ɪvɪsəˈreɪʃən/) is disembowelment, i.e., the removal of viscera (internal organs, especially those in the abdominal cavity). The term may also refer to: * Evisceration (autotomy), ejection of viscera as a defe ...
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 Green, L.E., Lewis, K., Kimpton, A. and Nicol, C.J., (2000). Cross-sectional study of the prevalence of feather pecking in laying hens in alternative systems and its associations with management and disease. Veterinary Record, 147: 233-238. 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
autopsy An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death or to evaluate any d ...
were different types of cannibalism (65.51%), with vent cannibalism (38.57%) the most common.Weitzenburger, D., Vits, A., Hamann, H. and Distl, O., (2005). Effect of furnished small group housing systems and furnished cages on mortality and causes of death in two layer strains. British Poultry Science, 46: 553-559 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 A furnished cage, sometimes called enriched cage, colony cage or modified cage, is a type of cage used in poultry farming for egg laying hens. Furnished cages have been designed to overcome some of the welfare concerns of battery cages (also cal ...
, with a similar rank for the severity of vent pecking injuries.Sherwin, C.M., Richards. G.J. and Nicol, C.J., (2010). Comparison of the welfare of layer hens in 4 housing systems in the UK. British Poultry Science, 51: 488-499


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 (FA), is a form of biological asymmetry, along with anti-symmetry and direction asymmetry. Fluctuating asymmetry refers to small, random deviations away from perfect bilateral symmetry. This deviation from perfection is thoug ...
,
heterophil Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying in ...
to
lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic a ...
ratio, and
tonic immobility Apparent death, colloquially known as playing dead, feigning death, or playing possum, is a behavior in which animals take on the appearance of being dead. It is an immobile state most often triggered by a predatory attack and can be found in a ...
duration.Campo, J.L., Prieto, M.T. and Dávila, S.G., (2008). Association between vent pecking and fluctuating asymmetry, heterophil to lymphocyte ratio, and tonic immobility duration in chickens. Applied Animal Behaviour Science, 113: 87-97 Vent pecking can be related to disease or immune challenge as it sometimes becomes prevalent in cases of Gumboro disease ( Infectious Bursal Disease)Butterworth, A. and Weeks, C., (2010). The impact of disease on welfare. In ''The Welfare of Domestic Fowl and Other Captive Birds'', I.J.H. Duncan and P. Hawkins (eds), Springer, pp. 189-218 and is increased by challenges with the protein antigen, human serum albumin (HuSA).Parmentier, H.K., Rodenburg, T.B., De Vries Reilingh, G., Beerda, B. and Kemp, B., (2009). Does enhancement of specific immune responses predispose laying hens for feather pecking? Poultry Science, 88: 536-542 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 Tauson, R., (1984). Effects of a perch in conventional cages for laying hens. Acta Agriculturae Scandinavica, 34: 193-209Glatz, P.C. and Barnett, J.L., (1996). Effect of perches and solid sides on production, plumage and foot condition of laying hens housed in conventional cages in a naturally ventilated shed. Australian Journal of Experimental Agriculture, 36: 269-275 and increased pecking activity and cannibalistic behaviour can occur due to inadequate height of the perches.Moinard, C., Morisse, J.P. and Faure, J.M., (1998). Effect of cage area, cage height, and perches on feather condition, bone breakage and mortality of laying hens. British Poultry Science, 39: 198-202Wechsler, B. and Huber-Eicher, B.,(1998). Haltungsbedingte Ursachen des Federpickens bei Huhnern. Agrarforschung, 5: 217-220 Larger group sizes lead to increases in vent pecking suggesting that social learning plays a role.


See also

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Abnormal behaviour of birds in captivity Abnormal behavior of birds in captivity has been found to occur among both domesticated and wild birds. Abnormal behavior can be defined in several ways. Statistically, 'abnormal' is when the occurrence, frequency or intensity of a behaviour varie ...
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Feather pecking Feather pecking is a behavioural problem that occurs most frequently amongst domestic hens reared for egg production,Huber-Eicher, B. and Sebo, F. 2001. The prevalence of feather pecking and development in commercial flocks of laying hens. Applie ...
*
Cannibalism (poultry) Cannibalism in poultry is the act of one individual of a poultry species consuming all or part of another individual of the same species as food. It commonly occurs in flocks of domestic hens reared for egg production, although it can also occur ...
*
Toe pecking Toe pecking, an abnormal behaviour of birds in captivity, occurs when one bird pecks the toes of another using its beak. This behaviour has been reported in hens and ostriches.Bubier N.E., Deeming, C. and Ayres L.L. (1996). Behaviour of ostric ...
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Chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...
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Poultry farming Poultry farming is the form of animal husbandry which raises domesticated birds such as chickens, ducks, turkeys and geese to produce meat or eggs for food. Poultry – mostly chickens – are farmed in great numbers. More than 60 billion ...
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Battery cages Battery cages are a housing system used for various animal production methods, but primarily for egg-laying hens. The name arises from the arrangement of rows and columns of identical cages connected together, in a unit, as in an artillery batt ...


References

{{Ethology Ethology Animal welfare Bird health Aviculture Abnormal behaviour in animals