In the United States, chickens were raised primarily on family farms or in some cases, in poultry colonies, until about 1960. Originally, the primary value in poultry keeping was eggs, and meat was considered a byproduct of egg production.
Poultry shows spread interest and understanding, with 88% of all farmers having chickens by 1910.
As the United States urbanized, demand for eggs grew. Eggs were sold into urban markets, where residents did not have chickens to provide eggs for themselves. Except in hot weather, eggs can be shipped and stored without
refrigeration for some time before going bad; this was important in the days before widespread refrigeration. With a steady demand for eggs, efforts to create a poultry egg industry began in earnest, but raising poultry remained challenging; early efforts at industrial-scale indoor poultry houses led to problems with diseases like
coccidiosis,
Marek's disease, and
vitamin D deficiency were not well understood.
The major milestone in 20th century poultry production was the discovery of
vitamin D (named in 1922), 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.
Artificial daylight supplementation also started being used.
Improvements in production and quality were accompanied by lower labor requirements. In the 1930s through the early 1950s, 1,500 hens was considered to be a full-time job for a farm family. 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 marked the beginning of the transition from
family farms to larger, vertically integrated operations.
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.
Today, eggs are produced on large egg ranches on which environmental parameters are controlled. Chickens are exposed to artificial light cycles to stimulate egg production year-round. In addition, it is a common practice to induce
molting through manipulation of light and the amount of food they receive in order to further increase egg size and production.
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 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.
brusselssignal.eu
tube.solari.com
