Commercial poultry feeding is a highly perfected science that ensures a maximum intake of energy for growth and fat production. High-quality and well-balanced protein sources produce a maximum amount of muscle, organ, skin, and feather growth. The essential minerals produce bones and eggs, with about 3 to 4 percent of the live bird being composed of minerals and 10 percent of the egg. Calcium , phosphorus , sodium , chlorine , potassium , sulfur , manganese , iron , copper , cobalt , magnesium , and zinc are all required. Vitamins A , C , D , E , and K and all of the B vitamins are also required. Antibiotics are widely used to stimulate appetite, control harmful bacteria , and prevent disease. For chickens, modern rations produce about 0.5 kg (1 pound) of broiler on about 0.9 kg (2 pounds) of feed and a dozen eggs from 2 kg (4.5 pounds) of feed.

A carefully controlled environment that avoids crowding, chilling, overheating, or frightening is almost universal in poultry farming. Cannibalism, which expresses itself as toe picking, feather picking, and tail picking, is controlled by debeaking at one day of age and by other management practices. The feeding, watering, egg gathering, and cleaning operations are highly mechanized. Birds are usually housed in wire cages with two or three animals per cage, depending on the species and breed, and three or four tiers of cages superposed to save space. Cages for egg-laying birds have been found to increase production, lower mortality, reduce cannibalism, lower feeding requirements, reduce diseases and parasites, improve culling, and reduce both space and labour requirements.

Single-comb White Leghorn hens housed for egg production in a multitiered layer house © Larry Lefever/Grant Heilman Photography, Inc.

Poultry breeding is an outstanding example of the application of basic genetic principles of inbreeding and crossbreeding as well as of intensive mass selection to effect faster and cheaper gains in meat and maximum egg production for the egg-laying strains. Maximum use of heterosis, or hybrid vigour, through incrosses and crossbreeding has been made. Rapid and efficient weight gains and high-quality, plump, meaty carcasses have been achieved thereby.

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Among the world’s agricultural industries, chicken breeding in the U.S. is one of the most advanced. Intensive nutritional research and application, highly improved breeding stock, intelligent management, and scientific disease control have gone into the effort to give a modern broiler (meat chicken) of uniformly high quality produced at ever-lower cost. A modern broiler chick can reach a 2.3-kg (5-pound) market weight in five weeks, compared with the four months that were required in the mid-20th century. Additionally, annual egg production per hen has increased from about 100 in 1910 to over 300 in the early 21st century.