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On average, a chicken lays one egg a day for a number of days (a "clutch"), then does not lay for one or more days, then lays another clutch. Originally, the hen presumably laid one clutch, became broody, and incubated the eggs. Selective breeding over the centuries has produced hens that lay more eggs than they can hatch. Some of this progress ...
Older hens gradually produce fewer eggs, and the eggs are usually larger. [1] Since the average lifespan of a pet layer hen is 8–15 years, [2] henopause has received attention as a potential problem for backyard or urban chicken farmers who are eventually faced with the decision to either slaughter older layers or keep them as non-producing pets.
The only living mammals that lay eggs are echidnas and platypuses. In the latter, the eggs develop in utero for about 28 days, with only about 10 days of external incubation (in contrast to a chicken egg, which spends about one day in tract and 21 days externally). [11] After laying her eggs, the female curls around them.
In the United States alone, more than 8 billion chickens are slaughtered each year for meat, [78] and more than 300 million chickens are reared for egg production. [79] The vast majority of poultry is raised in factory farms. According to the Worldwatch Institute, 74% of the world's poultry meat and 68% of eggs are produced this way. [80]
Hamburger and Hamilton aimed to provide a detailed description of developmental events, modeled on an earlier system for Axolotl by Harrison. The Hamburger–Hamilton system provides advantages over the Carnegie system in that it allows the developing chick to be accurately characterized during all embryonic stages, and is used universally in ...
On average, a chicken lays one egg a day, but not on every day of the year. This varies with the breed and time of year. In 1900, average egg production was 83 eggs per hen per year. In 2000, it was well over 300. In the United States, laying hens are butchered after their second egg laying season.
The broiler industry is the process by which broiler chickens are reared and prepared for meat consumption. Worldwide, in 2005 production was 71,851,000 tonnes. From 1985 to 2005, the broiler industry grew by 158%. [1] A key measure of performance is the feed conversion ratio (FCR), the ability to convert feed into edible product.
A dual-purpose chicken is a type of chicken that may be used in the production of both eggs and meat. [42] In the past, many chicken breeds were selected for both functions. However, since the advent of laying and meat hybrids, industrial chicken breeding has made a sharp distinction between chickens with either function, [ 43 ] so that certain ...