家禽
Poultry/ja
家禽 (/ˈpoʊltri/) は、人間が肉、卵、羽毛などの動物性生産物を得る目的で飼育する家畜化された鳥類である。家禽を飼育する行為は養鶏業として知られている。これらの鳥は、通常は鳥類（特にキジ目に属するニワトリ、ウズラ、七面鳥など）を含むキジカモ目の構成員である。また、カモやガチョウなどカモ科に属する水禽も含まれるが、食料として狩猟される猟鳥やジビエは含まれない。
現存する4種のヤケイを対象とする最近のゲノミクス研究は、最も個体数の多い家禽種であるニワトリの家畜化が、約8,000年前に東南アジアで起こったことを示す。これは以前には、同じく東南アジアで約5,400年前に起こったと考えられていた。この過程は、当初は野生から採取した卵を孵化させて幼鳥を育てることによって生じた可能性があるが、のちには鳥を恒久的に飼育下に置くことを伴うようになった。家畜化されたニワトリは初めは闘鶏に用いられ、ウズラは鳴き声のために飼われた可能性があるが、人々はやがて飼育下繁殖による食料源を持つ利点に気づいた。急速な成長、産卵能力、体型、羽色、従順さに関する選択育種が数世紀にわたって行われ、現代の品種はしばしば野生の祖先とは大きく異なる外見をしている。いまだに一部の鳥は広範な飼養体系において小規模な群れで飼われているが、今日市場で入手可能な大多数の鳥は集中的な商業事業で飼育されている。
豚肉と並んで、家禽は世界で最も広く食べられている2種類の肉のひとつであり、2012年には両者で肉供給の70%以上を占めていた。家禽は高品質のタンパク質を含み、脂肪の割合が低い栄養上有益な食料を提供する。すべての家禽肉は、食中毒のリスクを減らすために適切に取り扱い、十分に調理されるべきである。家禽のみを肉の唯一の供給源として摂取するセミベジタリアンは、ポロタリアニズムを実践しているとされる。
語源
「poultry」という語は、中英語の pultry または pultrie に由来し、これはさらに古フランス語/ノルマン語の pouletrie に由来する。未成熟な家禽を指す若雌鶏という語は、その二重語である poult と同様に、中英語 pulet および古フランス語 polet に由来し、どちらもラテン語の pullus（幼い鳥または幼い動物を意味する）に遡る。語「fowl」はゲルマン語派起源であり（古英語 Fugol、ドイツ語 Vogel、デンマーク語 Fugl に比較される）。
定義
「Poultry」は、いかなる種類の家畜化された鳥でも、その有用性のために飼育下で繁殖されたものを指す用語であり、伝統的にこの語は野禽（キジ目）や水禽（カモ目）を指すが、かご鳥、例えば鳴禽やオウムは含まない。「Poultry」は、肉や卵の生産のために飼育される家禽、すなわちニワトリ、七面鳥、ガチョウ、カモを含む家禽類として定義でき、また食用として用いられるこれらの鳥の肉を指す語としても用いられる。
The Encyclopædia Britannica は同じ鳥類群を挙げているが、ホロホロチョウやスカウォブ（若いハト）も含めている。R. D. Crawford の『Poultry breeding and genetics』ではスカウォブは除外されているが、日本ウズラとコウライキジが追加されており、後者はしばしば飼育下で繁殖されて野に放たれる。Edmund Dixon の1848年の古典的著作『Ornamental and Domestic Poultry: Their History, and Management』には、クジャク、ホロホロチョウ、コブハクチョウ、シチメンチョウ、各種のガチョウ、ムスコビーダック、その他のカモ類、バンタムを含むあらゆる種類のニワトリに関する章が含まれている。
口語では、「fowl」という語はしばしば「家畜化されたニワトリ」（Gallus gallus）や「家禽」あるいは単に「鳥」とほぼ同義に用いられ、多くの言語では「poultry」と「fowl」を区別しない。両語はこれらの鳥の肉を指すためにも用いられる。家禽は「game」と区別され、これは食料またはスポーツのために狩猟される野鳥や哺乳類を意味し、これらを食べる際の肉を表す語としても用いられる。
例
| 鳥 | 野生の祖先 | 家畜化 | 利用 | 画像 |
|---|---|---|---|---|
| ニワトリ | セキショクヤケイ | 南および東南アジア | 卵と肉 | 
|
| 七面鳥 | 野生のシチメンチョウ | メキシコ | 肉 | 
|
| 家禽ウズラ | ウズラ | 各地 | 卵と肉 | 
|
| アヒル | マガモ | 各地 | 卵、肉、羽毛 | 
|
| ガチョウ | ハイイロガン | 各地 | 卵、肉、羽毛 | 
|
| ホロホロチョウ | ホロホロチョウ | アフリカ | 卵と肉 | 
|
| 家鳩 | カワラバト | ユーラシア | 肉 | 
|
ニワトリ
ニワトリは中型でずんぐりした体格をもち、直立姿勢をとる鳥で、頭部に赤い肉質の鶏冠と肉垂を備えることが特徴である。雄（cock）は通常、雌（hen）よりも大きく、より大胆な体色を示し、雌より誇張された羽装をもつ。ニワトリは群生的な雑食性の地上性鳥類であり、自然環境では落ち葉の中で種子、無脊椎動物、その他の小動物を探して採食する。接近されると下生えに走り込むことを好み、知覚された危険による場合を除き、めったに飛翔しない。今日の家禽ニワトリ（Gallus gallus domesticus）は、主としてアジアの野生セキショクヤケイに由来し、さらにハイイロヤケイ、スリランカヤケイ、ミドリヤケイからの追加的な寄与がある。
Genomic studies estimate that the chicken was domesticated 8,000 years ago in Southeast Asia and spread to China and India 2000–3000 years later. Archaeological evidence supports domestic chickens in Southeast Asia well before 6000 BC, China by 6000 BC and India by 2000 BC. A landmark 2020 Nature study that fully sequenced 863 chickens across the world suggests that all domestic chickens originate from a single domestication event of red junglefowl whose present-day distribution is predominantly in southwestern China, northern Thailand and Myanmar. These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups. Analysis of the most popular commercial breed shows that the White Leghorn breed possesses a mosaic of divergent ancestries inherited from subspecies of red junglefowl.
Chickens were one of the domesticated animals carried with the sea-borne Austronesian migrations into Taiwan, Island Southeast Asia, Island Melanesia, Madagascar, and the Pacific Islands; starting from around 3500 to 2500 BC.
By 2000 BC, chickens seem to have reached the Indus Valley and 250 years later, they arrived in Egypt. They were still used for fighting and were regarded as symbols of fertility. The Romans used them in divination, and the Egyptians made a breakthrough when they learned the difficult technique of artificial incubation. Since then, the keeping of chickens has spread around the world for the production of food with the domestic fowl being a valuable source of both eggs and meat.
Since their domestication, a large number of breeds of chickens have been established, but with the exception of the white Leghorn, most commercial birds are of hybrid origin. In about 1800, chickens began to be kept on a larger scale, and modern high-output poultry farms were present in the United Kingdom from around 1920 and became established in the United States soon after the Second World War. By the mid-20th century, the poultry meat-producing industry was of greater importance than the egg-laying industry. Poultry breeding has produced breeds and strains to fulfil different needs; light-framed, egg-laying birds that can produce 300 eggs a year; fast-growing, fleshy birds destined for consumption at a young age, and utility birds which produce both an acceptable number of eggs and a well-fleshed carcase. Male birds are unwanted in the egg-laying industry and can often be identified as soon as they are hatch for subsequent culling. In meat breeds, these birds are sometimes castrated (often chemically) to prevent aggression. The resulting bird, called a capon, has more tender and flavorful meat, as well.
A bantam is a small variety of domestic chicken, either a miniature version of a member of a standard breed, or a "true bantam" with no larger counterpart. The name derives from the town of Bantam in Java where European sailors bought the local small chickens for their shipboard supplies. Bantams may be a quarter to a third of the size of standard birds and lay similarly small eggs. They are kept by small-holders and hobbyists for egg production, use as broody hens, ornamental purposes, and showing.
Cockfighting
Cockfighting is said to be the world's oldest spectator sport. Two mature males (cocks or roosters) are set to fight each other, and will do so with great vigour until one is critically injured or killed. Cockfighting is extremely widespread in Island Southeast Asia, and often had ritual significance in addition to being a gambling sport. They also formed part of the cultures of ancient India, China, Persia, Greece, Rome, and large sums were won or lost depending on the outcome of an encounter. Breeds such as the Aseel were developed in the Indian subcontinent for their aggressive behaviour. Cockfighting has been banned in many countries during the last century on the grounds of cruelty to animals.
Ducks
Ducks are medium-sized aquatic birds with broad bills, eyes on the side of the head, fairly long necks, short legs set far back on the body, and webbed feet. Males, known as drakes, are often larger than females (known as hens) and are differently coloured in some breeds. Domestic ducks are omnivores, eating a variety of animal and plant materials such as aquatic insects, molluscs, worms, small amphibians, waterweeds, and grasses. They feed in shallow water by dabbling, with their heads underwater and their tails upended. Most domestic ducks are too heavy to fly, and they are social birds, preferring to live and move around together in groups. They keep their plumage waterproof by preening, a process that spreads the secretions of the preen gland over their feathers.
Clay models of ducks found in China dating back to 4000 BC may indicate the domestication of ducks took place there during the Yangshao culture. Even if this is not the case, domestication of the duck took place in the Far East at least 1500 years earlier than in the West. Lucius Columella, writing in the first century BC, advised those who sought to rear ducks to collect wildfowl eggs and put them under a broody hen, because when raised in this way, the ducks "lay aside their wild nature and without hesitation breed when shut up in the bird pen". Despite this, ducks did not appear in agricultural texts in Western Europe until about 810 AD, when they began to be mentioned alongside geese, chickens, and peafowl as being used for rental payments made by tenants to landowners.
It is widely agreed that the mallard (Anas platyrhynchos) is the ancestor of all breeds of domestic duck (with the exception of the Muscovy duck (Cairina moschata), which is not closely related to other ducks). Ducks are farmed mainly for their meat, eggs, and down. As is the case with chickens, various breeds have been developed, selected for egg-laying ability, fast growth, and a well-covered carcase. The most common commercial breed in the United Kingdom and the United States is the Pekin duck, which can lay 200 eggs a year and can reach a weight of 3.5 kg (7 lb 11 oz) in 44 days. In the Western world, ducks are not as popular as chickens, because the latter produce larger quantities of white, lean meat and are easier to keep intensively, making the price of chicken meat lower than that of duck meat. While popular in haute cuisine, duck appears less frequently in the mass-market food industry. However, things are different in the East. Ducks are more popular there than chickens and are mostly still herded in the traditional way and selected for their ability to find sufficient food in harvested rice fields and other wet environments.
Goose
The greylag goose (Anser anser) was domesticated by the Egyptians at least 3000 years ago, and a different wild species, the swan goose (Anser cygnoides), domesticated in Siberia about a thousand years later, is known as a Chinese goose. The two hybridise with each other and the large knob at the base of the beak, a noticeable feature of the Chinese goose, is present to a varying extent in these hybrids. The hybrids are fertile and have resulted in several of the modern breeds. Despite their early domestication, geese have never gained the commercial importance of chickens and ducks.
Domestic geese are much larger than their wild counterparts and tend to have thick necks, an upright posture, and large bodies with broad rear ends. The greylag-derived birds are large and fleshy and used for meat, while the Chinese geese have smaller frames and are mainly used for egg production. The fine down of both is valued for use in pillows and padded garments. They forage on grass and weeds, supplementing this with small invertebrates, and one of the attractions of rearing geese is their ability to grow and thrive on a grass-based system. They are very gregarious and have good memories and can be allowed to roam widely in the knowledge that they will return home by dusk. The Chinese goose is more aggressive and noisy than other geese and can be used as a guard animal to warn of intruders. The flesh of meat geese is dark-coloured and high in protein, but they deposit fat subcutaneously, although this fat contains mostly monounsaturated fatty acids. The birds are killed either around 10 or about 24 weeks. Between these ages, problems with dressing the carcase occur because of the presence of developing pin feathers.
In some countries, geese and ducks are force-fed to produce livers with an exceptionally high fat content for the production of foie gras. Over 75% of world production of this product occurs in France, with lesser industries in Hungary and Bulgaria and a growing production in China. Foie gras is considered a luxury in many parts of the world, but the process of feeding the birds in this way is banned in many countries on animal welfare grounds.
Turkeys
Turkeys are large birds, their nearest relatives being the pheasant and the guineafowl. Males are larger than females and have spreading, fan-shaped tails and distinctive, fleshy wattles, called a snood, that hang from the top of the beak and are used in courtship display. Wild turkeys can fly, but seldom do so, preferring to run with a long, straddling gait. They roost in trees and forage on the ground, feeding on seeds, nuts, berries, grass, foliage, invertebrates, lizards, and small snakes.
The modern domesticated turkey is descended from one of six subspecies of wild turkey (Meleagris gallopavo) found in the present Mexican states of Jalisco, Guerrero and Veracruz. Pre-Aztec tribes in south-central Mexico first domesticated the bird around 800 BC, and Pueblo Indians inhabiting the Colorado Plateau in the United States did likewise around 200 BC. They used the feathers for robes, blankets, and ceremonial purposes. More than 1,000 years later, they became an important food source. The first Europeans to encounter the bird misidentified it as a guineafowl, a bird known as a "turkey fowl" at that time because it had been introduced into Europe via Turkey.
Commercial turkeys are usually reared indoors under controlled conditions. These are often large buildings, purpose-built to provide ventilation and low light intensities (this reduces the birds' activity and thereby increases the rate of weight gain). The lights can be switched on for 24 h/day, or a range of step-wise light regimens to encourage the birds to feed often and therefore grow rapidly. Females achieve slaughter weight at about 15 weeks of age and males at about 19. Mature commercial birds may be twice as heavy as their wild counterparts. Many different breeds have been developed, but the majority of commercial birds are white, as this improves the appearance of the dressed carcass, the pin feathers being less visible. Turkeys were at one time mainly consumed on special occasions such as Christmas (10 million birds in the United Kingdom) or Thanksgiving (60 million birds in the United States). However, they are increasingly becoming part of the everyday diet in many parts of the world.
Other poultry
Guineafowl originated in southern Africa, and the species most often kept as poultry is the helmeted guineafowl (Numida meleagris). It is a medium-sized grey or speckled bird with a small naked head with colorful wattles and a knob on top, and was domesticated by the time of the ancient Greeks and Romans. Guineafowl are hardy, sociable birds that subsist mainly on insects, but also consume grasses and seeds. They will keep a vegetable garden clear of pests and will eat the ticks that carry Lyme disease. They happily roost in trees and give a loud vocal warning of the approach of predators. Their flesh and eggs can be eaten in the same way as chickens, young birds being ready for the table at the age of about four months.
A squab is the name given to the young of domestic pigeons that are destined for the table. Like other domesticated pigeons, birds used for this purpose are descended from the rock dove (Columba livia). Special utility breeds with desirable characteristics are used. Two eggs are laid and incubated for about 17 days. When they hatch, the squabs are fed by both parents on "pigeon's milk", a thick secretion high in protein produced by the crop. Squabs grow rapidly, but are slow to fledge and are ready to leave the nest at 26 to 30 days weighing about 500 g (1 lb 2 oz). By this time, the adult pigeons will have laid and be incubating another pair of eggs and a prolific pair should produce two squabs every four weeks during a breeding season lasting several months.
Poultry farming
Worldwide, more chickens are kept than any other type of poultry, with over 50 billion birds being raised each year as a source of meat and eggs. Traditionally, such birds would have been kept extensively in small flocks, foraging during the day and housed at night. This is still the case in developing countries, where the women often make important contributions to family livelihoods through keeping poultry. However, rising world populations and urbanization have led to the bulk of production being in larger, more intensive specialist units. These are often situated close to where the feed is grown or near to where the meat is needed, and result in cheap, safe food being made available for urban communities. Profitability of production depends very much on the price of feed, which has been rising. High feed costs could limit further development of poultry production.
In free-range husbandry, the birds can roam freely outdoors for at least part of the day. Often, this is in large enclosures, but the birds have access to natural conditions and can exhibit their normal behaviours. A more intensive system is yarding, in which the birds have access to a fenced yard and poultry house at a higher stocking rate. Poultry can also be kept in a barn system, with no access to the open air, but with the ability to move around freely inside the building. The most intensive system for egg-laying chickens is battery cages, often set in multiple tiers. In these, several birds share a small cage which restricts their ability to move around and behave in a normal manner. The eggs are laid on the floor of the cage and roll into troughs outside for ease of collection. Battery cages for hens have been illegal in the EU since January 1, 2012.
Chickens raised intensively for their meat are known as "broilers". Breeds have been developed that can grow to an acceptable carcass size (2 kg or 4 lb 7 oz) in six weeks or less. Broilers grow so fast, their legs cannot always support their weight and their hearts and respiratory systems may not be able to supply enough oxygen to their developing muscles. Mortality rates at 1% are much higher than for less-intensively reared laying birds which take 18 weeks to reach similar weights. Processing the birds is done automatically with conveyor-belt efficiency. They are hung by their feet, stunned, killed, bled, scalded, plucked, have their heads and feet removed, eviscerated, washed, chilled, drained, weighed, and packed,all within the course of little over two hours.
Both intensive and free-range farming have animal welfare concerns. In intensive systems, cannibalism, feather pecking and vent pecking can be common, with some farmers using beak trimming as a preventative measure. Diseases can also be common and spread rapidly through the flock. In extensive systems, the birds are exposed to adverse weather conditions and are vulnerable to predators and disease-carrying wild birds. Barn systems have been found to have the worst bird welfare. In Southeast Asia, a lack of disease control in free-range farming has been associated with outbreaks of avian influenza.
Poultry shows
In many countries, national and regional poultry shows are held where enthusiasts exhibit their birds which are judged on certain phenotypical breed traits as specified by their respective breed standards. The idea of poultry exhibition may have originated after cockfighting was made illegal, as a way of maintaining a competitive element in poultry husbandry. Breed standards were drawn up for egg-laying, meat-type, and purely ornamental birds, aiming for uniformity. Sometimes, poultry shows are part of general livestock shows, and sometimes they are separate events such as the annual "National Championship Show" in the United Kingdom organised by the Poultry Club of Great Britain.
Poultry as food
Trade
Poultry is the second most widely eaten type of meat in the world, accounting for about 30% of total meat production worldwide compared to pork at 38%. Sixteen billion birds are raised annually for consumption, more than half of these in industrialised, factory-like production units. Global broiler meat production rose to 84.6 million tonnes in 2013. The largest producers were the United States (20%), China (16.6%), Brazil (15.1%) and the European Union (11.3%). There are two distinct models of production; the European Union supply chain model seeks to supply products which can be traced back to the farm of origin. This model faces the increasing costs of implementing additional food safety requirements, welfare issues and environmental regulations. In contrast, the United States model turns the product into a commodity.
World production of duck meat was about 4.2 million tonnes in 2011 with China producing two thirds of the total, some 1.7 billion birds. Other notable duck-producing countries in the Far East include Vietnam, Thailand, Malaysia, Myanmar, Indonesia and South Korea (12% in total). France (3.5%) is the largest producer in the West, followed by other EU nations (3%) and North America (1.7%). China was also by far the largest producer of goose and guinea fowl meat, with a 94% share of the 2.6 million tonne global market.
Global egg production was expected to reach 65.5 million tonnes in 2013, surpassing all previous years. Between 2000 and 2010, egg production was growing globally at around 2% per year, but since then growth has slowed down to nearer 1%. In 2018, egg production reached 76.7 million tonnes, a huge 24% growth since 2008.
Cuts of poultry
Poultry is available fresh or frozen, as whole birds or as joints (cuts), bone-in or deboned, seasoned in various ways, raw or ready cooked. The meatiest parts of a bird are the flight muscles on its chest, called "breast" meat, and the walking muscles on the legs, called the "thigh" and "drumstick". The wings are also eaten (Buffalo wings are a popular example in the United States) and may be split into three segments, the meatier "drumette", the "wingette" (also called the "flat"), and the wing tip (also called the "flapper"). In Japan, the wing is frequently separated, and these parts are referred to as 手羽元 (teba-moto "wing base") and 手羽先 (teba-saki "wing tip").
Dark meat, which avian myologists refer to as "red muscle", is used for sustained activity—chiefly walking, in the case of a chicken. The dark color comes from the protein myoglobin, which plays a key role in oxygen uptake and storage within cells. White muscle, in contrast, is suitable only for short bursts of activity such as, for chickens, flying. Thus, the chicken's leg and thigh meat are dark, while its breast meat (which makes up the primary flight muscles) is white. Other birds with breast muscle more suitable for sustained flight, such as ducks and geese, have red muscle (and therefore dark meat) throughout. Some cuts of meat including poultry expose the microscopic regular structure of intracellular muscle fibrils which can diffract light and produce iridescent colors, an optical phenomenon sometimes called structural coloration.
Health and disease (humans)
As of 2022, no clinical trials have assessed poultry intake on human health. Poultry meat and eggs provide nutritionally beneficial food containing protein of high quality. This is accompanied by low levels of fat which have a favourable mix of fatty acids. Chicken meat contains about two to three times as much polyunsaturated fat as most types of red meat when measured by weight. However, for boneless, skinless chicken breast, the amount is much lower. 100 grams (3.5 oz) of raw chicken breast contains 2 grams (0.071 oz) of fat and 22 grams (0.78 oz) of protein, compared to 9 grams (0.32 oz) of fat and 20 grams (0.71 oz) of protein for the same portion of raw beef flank steak.
A 2011 study by the Translational Genomics Research Institute showed that 47% of the meat and poultry sold in United States grocery stores was contaminated with Staphylococcus aureus, and 52% of the bacteria concerned showed resistance to at least three groups of antibiotics. Thorough cooking of the product would kill these bacteria, but a risk of cross-contamination from improper handling of the raw product is still present. Also, some risk is present for consumers of poultry meat and eggs to bacterial infections such as Salmonella and Campylobacter. Poultry products may become contaminated by these bacteria during handling, processing, marketing, or storage, resulting in food-borne illness if the product is improperly cooked or handled.
In general, avian influenza is a disease of birds caused by bird-specific influenza A virus that is not normally transferred to people; however, people in contact with live poultry are at the greatest risk of becoming infected with the virus and this is of particular concern in areas such as Southeast Asia, where the disease is endemic in the wild bird population and domestic poultry can become infected. The virus possibly could mutate to become highly virulent and infectious in humans and cause an influenza pandemic.
Bacteria can be grown in the laboratory on nutrient culture media, but viruses need living cells in which to replicate. Many vaccines to infectious diseases can be grown in fertilised chicken eggs. Millions of eggs are used each year to generate the annual flu vaccine requirements, a complex process that takes about six months after the decision is made as to what strains of virus to include in the new vaccine. A problem with using eggs for this purpose is that people with egg allergies are unable to be immunised, but this disadvantage may be overcome as new techniques for cell-based rather than egg-based culture become available. Cell-based culture will also be useful in a pandemic when it may be difficult to acquire a sufficiently large quantity of suitable sterile, fertile eggs.
関連項目
 | この記事は、クリエイティブ・コモンズ・表示・継承ライセンス3.0のもとで公表されたウィキペディアの項目Poultry(28 June 2025, at 22:13編集記事参照)を翻訳して二次利用しています。 |