谈心谈话记录范文:鸡（英语简介）

A chicken (Gallus gallus) is a type of domesticated bird which is often raised as a type of poultry. It is believed to be descended from the wild Asian Red Junglefowl.

Chickens are the most common bird in the world. The population in 2003 was 24 billion, according to the Firefly Encyclopedia of Birds.

General biology and habitat

White Leghorn ChickenMale chickens are known as roosters (in the U.S., Canada and Australia), cocks, or cockerels if they are young. Female chickens are known as hens, or 'chooks' in Australasian English. Roosters can usually be differentiated from hens by their striking plumage, marked by long flowing tails and bright pointed feathers on their necks.

However in some breeds, such as the Sebright, the cock only has slightly pointed neck feathers, and the identification must be made by looking at the comb. Chickens have a flesh crest on their heads called a comb and a fleshy piece of hanging skin under their beak called a wattle. These organs help to cool the bird by redirecting bloodflow to the skin. Both the male and female have distinctive wattles and combs. In males, the combs are often more prominent, though this is not the case in all varieties.

Chickens are often kept in gardens, not just in farms, and can make loving and gentle pets.

Chickens are omnivores and will feed on small seeds, herbs and leaves, grubs, insects and even small mammals like mice, if they can get them. Domestic chickens are typically fed commercially prepared feed that includes a protein source as well as grains. Chickens often scratch at the soil to get at adult insects and larva or seed. Incidents of cannibalism can occur when a curious bird pecks at a pre-existing wound or from over-crowding. This is exacerbated in close quarters. In commercial production this is controlled with chick "debeaking" (removal of 2/3 of the top half and 1/3 of the lower half of the beak). This "debeaking" process is painful for chickens because their beaks are filled with nerve endings.

Domestic chickens are not capable of flying for long distances, although they are generally capable of flying for short distances such as over fences. Chickens will sometimes fly simply in order to explore their surroundings, but will especially fly in an attempt to flee when they perceive danger. Because of the risk of flight, chickens raised in the open air generally have one of their wings clipped by the breeder — the tips of the longest feathers on one of the wings are cut, resulting in unbalanced flight which the bird cannot sustain for more than a few meters. (more on wing clipping)

Chicken eggs vary in color depending on the hen, typically ranging from bright white to shades of brown and even blue or green (Auracana varieties).Chickens are gregarious birds and live together as a flock. They have a communal approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing a "pecking order", with dominant individuals having priority for access to food and nesting locations. Removing hens or roosters from a flock causes a temporary disruption to this social order until a new pecking order is established.

Chickens will try to lay in nests that already contain eggs, and have been known to move eggs from neighbouring nests into their own. Some farmers use fake eggs made from plastic or stone to encourage hens to lay in a particular location. The result of this behaviour is that a flock will use only a few preferred locations, rather than having a different nest for every bird.

Hens can also be extremely stubborn about always laying in the same location. It is not unknown for two (or more) hens to try to share the same nest at the same time. If the nest is small, or one of the hens is particularly determined, this may result in chickens trying to lay on top of each other.

Contrary to popular belief, roosters may crow at anytime of the day. Their crowing - a loud and sometimes shrill call - is a territorial signal to other roosters.

Chickens are domesticated descendents of the red junglefowl, which is biologically classified as the same species.

Recent studies [1] have shown that chickens (and possibly other bird species) still retain the genetic blueprints to produce teeth in the jaws, although these are dormant in living animals. These are a holdover from primitive birds such as Archaeopteryx, which were descended from theropod dinosaurs.

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Courting
When a rooster finds food he may call the other chickens to eat it first. He does this by clucking in a high pitch as well as picking up and dropping the food. This is part of chicken courting ritual. When a hen is used to coming to his "call" the rooster may mount the hen and fertilize her egg.

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Going broody
Sometimes a hen will stop laying and instead will focus on the incubation of eggs, a state that is commonly known as going broody. A broody chicken will sit fast on the nest, and protest if disturbed or removed, and will rarely leave the nest to eat, drink, or dust bathe. While broody, the hen keeps the eggs at a constant temperature and humidity, as well as turning the eggs regularly.

At the end of the incubation period, which is an average of 21 days, the eggs (if fertilized) will hatch, and the broody hen will take care of her young. Since individual eggs do not all hatch at exactly the same time (the chicken can only lay one egg approximately every 25 hours), the hen will usually stay on the nest for about two days after the first egg hatches. During this time, the newly-hatched chicks live off the egg yolk they absorb just before hatching. The hen can hear the chicks peeping inside the eggs, and will gently cluck to encourage them to break out of their shells. If the eggs are not fertilized and do not hatch, the hen will eventually grow tired of being broody and leave the nest.

Modern egg-laying breeds rarely go broody, and those that do often stop part-way through the incubation cycle. Some breeds, such as the Cochin, Cornish and Silkie, regularly go broody and make excellent mothers.

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Artificial incubation
Chicken egg incubation can successfully occur artificially as well. Nearly all chicken eggs will hatch after 21 days of good conditions - 98-100 degrees fahrenheit (38°C) and around 65% relative humidity (may decrease to 55% in the last three days of incubation.) Many commercial incubators are industrial sized with shelves holding tens of thousands of eggs at a time, with rotation of the eggs a fully automated process.

Home incubators are usually small boxes (styrofoam incubators are popular) and hold 50 eggs. Eggs must be turned three to five times each day, rotating at least 90 degrees. If eggs aren't turned, the embryo inside will stick to the shell and likely will be born with physical defects. This process is natural: hens will stand up three to five times a day and shift the eggs around with their beak.

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Chickens as food

The USDA classifies cuts of poultry in a manner similar to beef.Chickens serve as one of the most common meats in the world, and are frequently prepared as food in a large number of ways. There is significant variation in cooking methods amongst cultures; historically common methods include roasting, baking, and frying. Today, chickens are also cooked by deep frying and prepared as fast food such as chicken nuggets. Modern varieties of chicken, such as the Cornish Cross, are bred specifically for meat production, with an emphasis placed on the ratio of feed to meat produced by the animal. In Chinese culinary culture, chicken is highly-valued, as in the phrase "无鸡不欢" (roughly translates as 'no chicken, no satisfaction').

Chickens raised specifically for meat are called broilers. In the United States, broilers are typically butchered at a young age. Modern Cornish Cross hybrids, for example, are butchered as early as 8 weeks for fryers and 12 weeks for roasting birds. Typically, the muscle tissue (breast, legs, thigh, etc), livers, and gizzard are processed for food. Chicken feet are less commonly eaten. The head, internal organs such as the lungs and intestines, and feathers are typically discarded or ground into a protein meal for inclusion in other animal feeds, although Chinese cuisines may retain the whole bird on the dish (with the head), depending on the dish.

Capons (castrated cocks) produce more and fattier meat than normal cocks. For this reason, they are considered a delicacy and were particularly popular in the Middle Ages. Caponizing a cock, unlike castrating a steer or pig, requires delicate surgery and is an art almost lost today. The cock's testicles lie within its body cavity. To remove them requires special equipment and skill. The person caponizing the rooster must make precise and specialized cuts within the abdomen of the rooster. Infection and potential damage to the bird are possible should an unskilled individual perform the surgery.

Roast ChickenChicken eggs, produced by pullets and laying hens, are also very commonly eaten. The chicken egg is the most commonly eaten bird egg in the world. Hens may lay fertile or infertile eggs. Hens will continue to lay even if a rooster is not present, though these will not be viable. There is no difference in the nutritional value between a fertilized and unfertilized egg. Modern breeding techniques focusing on feed-to-egg conversion ratios have increased the number of eggs a hen can lay. Modern egg chickens are typically derived from the early Leghorn varieties. When the egg is laid, the egg is not soft but has a hard shell. This shell protects the egg's contents, making it a food source that is easily transported and stored. Nutritionally, the egg provides a rich source of protein and vitamins. Recent concerns over cholesterol, however, have caused many to question the place of eggs in the human diet.

Some chicken breeds are raised for both meat and egg production. Typically heavy breeds, these are primarily grown by small farmers or hobbyists. These include breeds such as the Wyandotte, Brahma, or Barred Rock.

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Chickens as pets
In Asia, chickens with striking plumage have long been kept for ornamental purposes, including feather-footed varieties such as the Cochin and Silkie from China and the extremely long-tailed (Phoenix) from Japan. Asian ornamental varieties were imported into the United States and Great Britain in the late 1800s. Poultry fanciers then began keeping these ornamental birds for exhibition, a practice that continues today. From these Asian breeds, distinctive American varieties of chickens have been developed.

Today, some cities in the United States still allow residents to keep live chickens as pets, although the practice is quickly disappearing. Individuals in rural communities commonly keep chickens for both ornamental and practical value. Some communities ban only roosters, allowing the quieter hens. Many zoos use chickens instead of insecticides to control insect populations.

Growing chickens can easily be tamed by feeding them a special treat such as mealworms in the palm of one's hand, and by being with them for at least ten minutes daily when they are young.

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Chickens in agriculture

A chicken at the 2005 Melbourne ShowIn the United States, chickens were once raised primarily on the family farm. Prior to about 1930, chicken was served for primarily on special occasions or on Sunday as the birds were typically more valued for their eggs than meat. Excess roosters or non-productive hens would be culled from the flock first for butchering. As cities developed and markets sprung up across the nation, live chickens from local farms could often be seen for sale in crates outside the market, to be butchered and cleaned onsite by the butcher.

With the advent of refrigeration, poultry production changed dramatically. Large farms and packing plants emerged that could grow birds by the thousands. Adult chickens could be sent to factories for butchering and processing into pre-packaged commercial products to be frozen or shipped fresh to markets or wholesalers. Large farms or factories could be established devoted solely to egg production and packaging. Once a meat consumed only occasionally, the common availability has made chicken a common and significant meat product within developed nations. Growing concerns over cholesterol in the 1980s and 1990s further resulted in increased consumption.

Similarly, egg production also changed with the development of automation and refrigeration. Today, eggs are grown on factory farms in highly controlled settings. Special varieties of chickens are fed special diets high in calcium and protein to stimulate maximum egg production. Chickens are exposed to artificial light cycles to stimulate egg production year-round. In addition, it is a common practice to force chickens to molt through the careful manipulation of light and the amount of food they receive in order to further increase egg production.

Often, people in Third World Countries keep chickens for their produce, meat and for their company.

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Issues with mass production
Many animal advocates object to killing chickens for food or object to the factory farm conditions under which they are raised. Commercial chicken production often involves raising the birds in large crowded rearing sheds that prevent the chickens from engaging in many of their natural behaviours. In 2004 8.9 billion chickens were slaughtered in the United States[2].

Another animal welfare issue is the use of genetic selection to create heavy large-breasted birds, which can lead to crippling leg disorders and heart failure for some of the birds. In addition, many scientists have raised concerns that companies growing one variety of bird for eggs or meat are much more susceptible to potentially devastating disease. For this reason, many scientists are promoting the conservation of heritage breeds to retain genetic diversity in the species.