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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.
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.
While a single specific cause is unknown, chronic egg laying is believed to be triggered by hormonal imbalances influenced by a series of external factors. [1] As in the domestic chicken, female parrots are capable of producing eggs without the involvement of a male – it is a biological process that may be triggered by environmental cues such as day length (days becoming longer, indicating ...
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 ...
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.
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.
Early battery cages were often used for selecting hens based on performance since it is easy to track how many eggs each hen is laying if only one hen is placed in a cage. Later, this was combined with artificial insemination, giving a technique where each egg's parentage is known. This method is still used today. [citation needed]
The RSPCA "Welfare standards for laying hens and pullets" indicates that the stocking rate must not exceed 1,000 birds per hectare (10 m 2 per hen) of range available and a minimum area of overhead shade/shelter of 8 m 2 per 1,000 hens must be provided. Free-range farming of egg-laying hens is increasing its share of the market.