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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 the upper beak. USA's UEP guidelines suggest that in egg laying strains of chickens, the length of the upper beak distal from the nostrils which remains following trimming, should be 2 to 3 mm.〔United Egg Producers Animal Husbandry Guidelines for U.S. Egg Laying Flocks, 2008〕 In the UK, the Farm Animal Welfare Council stated: "The accepted procedure is to remove not more than one third of the upper and lower beaks or not more than one third of the upper beak only" but went on to recommend: "Where beak trimming is carried out, it should, wherever possible, be restricted to beak tipping; that is the blunting of the beak to remove the sharp point which can be the cause of the most severe damage to other birds."〔(【引用サイトリンク】title=FAWC opinion on beak trimming, 2007 )〕 The term "debeaking" implies that the entire beak is removed during the trimming process, though in reality only half or less of the beak is removed.〔Glatz, P.C., (2005). ''Poultry Welfare Issues: Beak Trimming.'' Nottingham University Press, Nottingham, United Kingdom.〕 Beak trimming is most common in egg-laying strains of chickens. In some countries such as the United States, turkeys are routinely beak trimmed, however, in the UK, only 10% of turkeys are beak trimmed.〔()〕 Beak trimming is a preventive measure to reduce damage caused by injurious pecking such as cannibalism, feather pecking and vent pecking, and thereby improve livability.〔 Commercial broiler chickens are not routinely beak trimmed as they reach slaughter weight at approximately 6 weeks of age, i.e. before injurious pecking usually begins. However, broiler breeding stock may be trimmed to prevent damage during mating.〔Gentle, M.J. and McKeegan, D.E.F., (2007). Evaluation of the effects of infrared beak trimming in broiler breeder chicks. Veterinary Record, 160: 145–148〕 In some countries, beak trimming is done as a last resort where alternatives are considered not to be possible or appropriate. Beak trimming has been banned in Switzerland since 1992. In close confinement, cannibalism, feather pecking and aggression are common among turkeys, ducks, pheasants, quail, and egg laying strains of chickens of many breeds (including both heritage breeds and modern hybrids). The tendency to cannibalism and feather pecking varies among different strains of chickens, but does not manifest itself consistently. Some flocks of the same breed may be entirely free from cannibalism, while others, under the same management, may have a serious outbreak. Mortalities mainly due to cannibalism can be up to 15% in egg laying flocks housed in aviaries,〔Hill, J.A., (1986). Egg production in alternative systems - a review of recent research in the UK. Research and Development in Agriculture, 3: 13-18〕 straw yards,〔Gibson, S.W., Dun, P. and Hughes, B.O., (1988). The performance and behaviour of laying fowls in a covered strawyard system. Research and Development in Agriculture, 5: 153-163〕 and free-range systems.〔Keeling, L.J., Hughes, B.O. and Dun P., (1988). Performance of free range laying hens in a polythene house and their behaviour on range. Farm Building Progress, 94: 21-28〕 Because egg laying strains of chickens can be kept in smaller group sizes in caged systems, cannibalism is reduced 〔Appleby, M.C. and Hughes B.O., (1991). Welfare of laying hens in cages and alternative systems: Environmental, physical and behavioural aspects. World's Poultry Science Journal, 47: 109-128〕〔Abrahamsson, P. and Tauson, R., (1995). Aviary systems and conventional cages for laying hens - effects on production, egg quality, health and bird location in 3 hybrids. Acta Agriculturae Scandinavica Section A-Animal Science, 45: 191-203〕 leading to a lowered trend in mortality as compared to non-cage systems. Cannibalism among flocks is highly variable and when it is not problematic, then mortalities among production systems are similar. 〔 == History == Beak trimming was developed at the Ohio Experiment Station in the 1930s.〔Kennard, D.C. (1937). ''Chicken Vices''. 184. Ohio Agricultural Experiment Station. 22: 33-39.〕 The original technique was temporary, cutting approximately 6 mm (1/4 inch) off the beak. It was thought that the tip of the beak had no blood supply and presumably no sensation. The procedure was performed by hand with a sharp knife, either when deaths due to cannibalism became excessive, or when the problem was anticipated because of a history of cannibalism in the particular strain of chicken. Cannibalism is a serious management problem dating back to the periods before intensive housing of poultry became popular. Poultry books written before vertical integration of the poultry industry describe the abnormal pecking of poultry:
Cannibalism has two peaks in the life of a chicken; during the brooding period and at the onset of egg laying. The point-of-lay cannibalism is generally the most damaging and gets most of the attention. The temporary beak trimming developed at the Ohio Experiment Station assumed that cannibalism was a phase, and that blunting the beak temporarily would be adequate. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Debeaking」の詳細全文を読む スポンサード リンク
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