CHICKEN English meaning
Mature males have long been used for sport (i.e., cockfighting, now outlawed in many jurisdictions) as well as for breeding. Farmers have developed numerous breeds and varieties to fulfill commercial requirements. Descendants of those domestications have spread throughout the world in khela88-bangladesh.com/ several waves for at least the last 2,000 years.
- In the United States alone, more than 8 billion chickens are slaughtered each year for meat, and more than 300 million chickens are reared for egg production.
- Hens often try to lay in nests that already contain eggs and sometimes move eggs from neighbouring nests into their own.
- Modern varieties however grow much faster; by day 35 a Ross 708 broiler may weigh 1.8 kg (4.0 lb) as against the 1.05 kg (2.3 lb) of a heritage chicken of the same age.
- Chickens give different warning calls to indicate that a predator is approaching from the air or on the ground.
- These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups.
Domestication and economic production
The chicks imprint on the hen and subsequently follow her continually. Eggs of chickens from the high-altitude region of Tibet have special physiological adaptations that result in a higher hatching rate in low oxygen environments. Hens often try to lay in nests that already contain eggs and sometimes move eggs from neighbouring nests into their own. As with all birds, reproduction is controlled by a neuroendocrine system, the Gonadotropin-Releasing Hormone-I neurons in the hypothalamus.
Reproduction and life-cycle
Chickens are descended primarily from the red junglefowl (Gallus gallus) and are scientifically classified as the same species. Wild junglefowl can fly, whereas domestic chickens and their flight muscles are too heavy to allow them to fly more than a short distance. Subsequent ovulations may occur within an hour after the previous egg was laid, allowing some hens to produce as many as 300 eggs per year. Egg laying is stimulated by the long stretches of daylight that occur during the warmer months; however, artificial lights placed in chicken coops can trigger a hen’s egg laying response throughout the year.
In groups of male chicks, however, fights for dominance may continue into adulthood. The pecking order is established within groups of female chicks by the 10th week of life. The time between ovulation and egg-laying is approximately 23–26 hours. In 2006, scientists researching the ancestry of birds switched on a chicken recessive gene, talpid2, and found that the embryo jaws initiated formation of teeth, like those found in ancient bird fossils. Large numbers of embryos can be provided commercially; fertilized eggs can easily be opened and used to observe the developing embryo.
Social hierarchy
Despite the chicken’s close relationship with the red jungle fowl, there is evidence that the gray jungle fowl (G. sonneratii) of southern India and other jungle fowl species, also members of Gallus, may have contributed to the bird’s ancestry. The chicken is a sacred animal in many cultures and deeply embedded in belief systems and religious practices.Roosters are sometimes used for divination, a practice called alectryomancy. This stimulates the hen to lose her feathers but also re-invigorates egg-production. In some other countries, flocks are sometimes force-moulted rather than being slaughtered to re-invigorate egg-laying.
Advocates of intensive farming say that their efficient systems save land and food resources owing to increased productivity, and that the animals are looked after in a controlled environment. Chickens are common and widespread domestic animals, with a total population of 23.7 billion as of 2018update. Breeding increased under the Roman Empire and reduced in the Middle Ages.