page_title: Intensive animal farming
section_title: Chickens
hierarchical_section_title: Intensive animal farming / Types / Chickens
caption_attribution_description: Battery hens English: Hens in battery cages in Bastos, São Paulo, Brazil.
context_page_description: Intensive animal farming or industrial livestock production, also known by its opponents as factory farming, is a type of intensive agriculture, specifically an approach to animal husbandry designed to maximize production, while minimizing costs. To achieve this, agribusinesses keep livestock such as cattle, poultry, and fish at high stocking densities, at large scale, and using modern machinery, biotechnology, and global trade. The main products of this industry are meat, milk and eggs for human consumption. There are issues regarding whether intensive animal farming is sustainable or ethical.
  There is a continuing debate over the benefits, risks and ethics of intensive animal farming. The issues include the efficiency of food production; animal welfare; health risks and the environmental impact. Social scientist Jacy Reese argues that for these reasons and the advent of animal-free food technology such as cultured meat, all animal farming will end by 2100.
context_section_description: The major milestone in 20th century poultry production was the discovery of vitamin D, which made it possible to keep chickens in confinement year-round. Before this, chickens did not thrive during the winter (due to lack of sunlight), and egg production, incubation, and meat production in the off-season were all very difficult, making poultry a seasonal and expensive proposition. Year-round production lowered costs, especially for broilers. 
  At the same time, egg production was increased by scientific breeding. After a few false starts, (such as the Maine Experiment Station's failure at improving egg production) success was shown by Professor Dryden at the Oregon Experiment Station.
  Improvements in production and quality were accompanied by lower labor requirements. In the 1930s through the early 1950s, 1,500 hens provided a full-time job for a farm family in America. In the late 1950s, egg prices had fallen so dramatically that farmers typically tripled the number of hens they kept, putting three hens into what had been a single-bird cage or converting their floor-confinement houses from a single deck of roosts to triple-decker roosts. Not long after this, prices fell still further and large numbers of egg farmers left the business. This fall in profitability was accompanied by a general fall in prices to the consumer, allowing poultry and eggs to lose their status as luxury foods.
  Robert Plamondon reports that the last family chicken farm in his part of Oregon, Rex Farms, had 30,000 layers and survived into the 1990s. However, the standard laying house of the current operators is around 125,000 hens.
  The vertical integration of the egg and poultry industries was a late development, occurring after all the major technological changes had been in place for years (including the development of modern broiler rearing techniques, the adoption of the Cornish Cross broiler, the use of laying cages, etc.).
  By the late 1950s, poultry production had changed dramatically. Large farms and packing plants could grow birds by the tens of thousands. Chickens could be sent to slaughterhouses for butchering and processing into prepackaged commercial products to be frozen or shipped fresh to markets or wholesalers. Meat-type chickens currently grow to market weight in six to seven weeks, whereas only fifty years ago it took three times as long. This is due to genetic selection and nutritional modifications (but not the use of growth hormones, which are illegal for use in poultry in the US and many other countries,  and have no effect). Once a meat consumed only occasionally, the common availability and lower cost has made chicken a common meat product within developed nations. Growing concerns over the cholesterol content of red meat in the 1980s and 1990s further resulted in increased consumption of chicken.
  Today, eggs are produced on large egg ranches on which environmental parameters are well controlled. Chickens are exposed to artificial light cycles to stimulate egg production year-round. In addition, forced molting is commonly practiced in the US, in which manipulation of light and food access triggers molting, in order to increase egg size and production. Forced molting is controversial, and is prohibited in the EU.
  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. In Europe, they are generally butchered after a single season. The laying period begins when the hen is about 18–20 weeks old (depending on breed and season). Males of the egg-type breeds have little commercial value at any age, and all those not used for breeding (roughly fifty percent of all egg-type chickens) are killed soon after hatching. The old hens also have little commercial value. Thus, the main sources of poultry meat 100 years ago (spring chickens and stewing hens) have both been entirely supplanted by meat-type
caption: Hens in Brazil
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