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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 UK alone consumes more than 34 million eggs per day. [84] Hens of some breeds can produce over 300 eggs per year; the highest authenticated rate of egg laying is 371 eggs in 364 days. [85] After 12 months of laying, the commercial hen's egg-laying ability declines to the point where the flock is commercially unviable.
All chickens lay eggs, have edible meat, and possess a unique appearance. However, distinct breeds are the result of selective breeding to emphasize certain traits. Any breed may be used for general agricultural purposes, and all breeds are shown to some degree. But each chicken breed is known for a primary use.
[4] [5] Due to modern selective breeding, laying hen strains differ from meat production strains . In the United States, males are culled in egg production because males "don't lay eggs or grow large enough to become broilers." [4] Ducklings and goslings are also culled in the production of foie gras.
In the early part of the twentieth century, it was one of the principal breeds kept for this purpose, until it was displaced by modern industrial hybrid lines. It may be kept as a dual-purpose bird. Hens lay some 180–200 tinted eggs per year; some layer strains may give up to 250. [7] The eggs weigh about 60 g. [9]
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.
In Leeds, England, in 1806 a hen began laying eggs on which the phrase "Christ is coming" was written. Eventually it was discovered to be a hoax. The owner, Mary Bateman, had written on the eggs in a corrosive ink so as to etch the eggs, and reinserted the eggs back into the hen's oviduct. [77] [78] 19 Oct 1814 Joanna Southcott
It has been suggested that the actions of a protein found in modern chicken eggs may make the answer different. [10] [11] In the uterus, chickens produce ovocleidin-17 (OC-17), which causes the formation of the thickened calcium carbonate shell around their eggs. Because OC-17 is expressed by the hen and not the egg, the bird in which the ...