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The dual-purpose chicken selected by the Lohmann group, the “Lohmann Dual”, [50] is raised in Switzerland by a few breeders, and the Coop network decided to launch the experiment with a test on 5,000 poultry, although knowing that instead of producing up to 300 eggs per year like very good laying hens, it will only produce around 250 eggs ...
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.
The relative activity of a species i, denoted a i, is defined [4] [5] as: = where μ i is the (molar) chemical potential of the species i under the conditions of interest, μ o i is the (molar) chemical potential of that species under some defined set of standard conditions, R is the gas constant, T is the thermodynamic temperature and e is the exponential constant.
For hens used in egg production in the US, as of 2011 the FCR was about 2, with each hen laying about 330 eggs per year. [25] When slaughtered, the world average layer flock as of 2013 yields a carcass FCR of 4.2, still much better than the average backyard chicken flock (FCR 9.2 for eggs, 14.6 for carcass). [26]
Selective breeding over the centuries has produced hens that lay more eggs than they can hatch. Some of this progress was ancient, but most occurred after 1900. 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.
Forced molting typically involves the removal of food and/or water from poultry for an extended period of time to reinvigorate egg-laying. Forced molting, sometimes known as induced molting, is the practice by some poultry industries of artificially provoking a flock to molt simultaneously, typically by withdrawing food for 7–14 days and sometimes also withdrawing water for an extended period.
Eggs laid by many different species, including birds, reptiles, amphibians, and fish, have probably been eaten by people for millennia. Popular choices for egg consumption are chicken, duck, roe, and caviar, but by a wide margin the egg most often humanly consumed is the chicken egg, typically unfertilized.
The first amniote egg – that is, a hard-shelled egg that could be laid on land, rather than remaining in water like the eggs of fish or amphibians – appeared around 312 million years ago. [6] In contrast, chickens are domesticated descendants of red junglefowl and probably arose little more than eight thousand years ago, at most. [7]