Chicken Types, Characteristics & Uses

In the UK and Europe, laying hens are then slaughtered and used in processed foods, or sold as ‘soup hens’. Hens of some breeds can produce over 300 eggs per year; the highest authenticated jaya9betting.com/ rate of egg-laying is 371 eggs in 364 days. During the Hellenistic period (4th–2nd centuries BC), in the southern Levant, chickens began to be widely domesticated for food.

Domestication and economic production

Under natural conditions, most birds lay only until a clutch is complete; they then incubate all the eggs. Adult chickens of both sexes have a fleshy crest on their heads called a comb or cockscomb, and hanging flaps of skin on either side under their beaks called wattles; combs and wattles are more prominent in males. In older sources, and still often in trade and scientific contexts, chickens as a species are described as common fowl or domestic fowl.

• These chickens may have been introduced during pre-Columbian times to South America via Polynesian seafarers, but this is disputed.
• For instance, many important discoveries in limb development have been made using chicken embryos, such as the discovery of the apical ectodermal ridge and the zone of polarizing activity.
• During the Hellenistic period (4th–2nd centuries BC), in the southern Levant, chickens began to be widely domesticated for food.
• Large numbers of embryos can be provided commercially; fertilized eggs can easily be opened and used to observe the developing embryo.
• Inbreeding of White Leghorn chickens tends to cause inbreeding depression expressed as reduced egg number and delayed sexual maturity.

Reproduction and life-cycle

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Many immature males (cockerels) are castrated (usually chemically, with hormones that cause atrophying of the testicles) to become meat birds (capons). The market for chicken meat has grown dramatically since then, with worldwide exports reaching nearly 12.5 million metric tons (about 13.8 million tons) by the early 21st century. By the mid-20th century, however, meat production had outstripped egg production as a specialized industry. For most of that period, chickens were a common part of the livestock complement of farms and ranches throughout Eurasia and Africa. Chicken domestication likely occurred more than once in Southeast Asia and possibly India over the most recent 7,400 years, and the first domestications may have been for religious reasons or for the raising of fighting birds. Each flock of chickens develops a social hierarchy that determines access to food, nesting sites, mates, and other resources.

Descendants of those domestications have spread throughout the world in several waves for at least the last 2,000 years. Chickens belonging to the same age cohort and sex are often kept together in industrial production settings. A flock usually includes one dominant adult male, a few subdominant males, and two or more females that are carefully watched over by the dominant male. Chicks are born covered in down, but they mature quickly, becoming fully feathered after four to five weeks.

A flock thus uses only a few preferred locations, rather than having a different nest for every bird. Reproduction declines with age, thought to be due to a decline in GnRH-I-N. If the female is unreceptive, she runs off; otherwise, she crouches, and the male mounts, treading with both feet on her back. Mating typically involves a sequence in which the male approaches the female and performs a waltzing display. The dance triggers a response in the hen and when she responds to his call, the rooster may mount the hen and proceed with the mating. To initiate courting, some roosters may dance in a circle around or near a hen (a circle dance), often lowering the wing which is closest to the hen.