In the United States, more than 300 million laying hens produce eggs, the majority of whom are confined in small, wire cages known as "battery cages." These "battery hens" suffer from a number of debilitating welfare problems, including the thwarting of natural behaviors, bone weakness and breakage, feather loss, and numerous diseases.
The life of a battery hen begins in a commercial hatchery, where thousands of chicks are hatched in industrial incubators. Male chicks are of no value to the egg industry and are killed shortly after birth, usually by gassing, crushing, or suffocation. The female chicks have part of their beaks seared off with a hot blade. This "beak trimming" is performed without anesthesia or analgesia. Chickens have pain receptors in their beaks, and research has shown that hens likely experience both acute and chronic pain as a result of "beak trimming." After this procedure, the chicks are transported to indoor egg farms and placed in battery cages.
Each wire battery cage normally houses three to ten hens. A typical U.S. egg farm contains thousands of cages at an average density of 59 square inches of space per bird (just over half the area of a letter-sized sheet of paper). Hens need an average of 72 square inches just to stand erect, 178 inches to preen, 197 inches to turn around, and 291 inches to flap their wings. Thus, hens in battery cages cannot perform any of these important natural behaviors, nor can they perch, preen, dustbathe, or nest. As a consequence, hens show signs of severe frustration and low welfare.
Battery cages contribute to a number of health problems, including uterine prolapse (when the uterus is pushed outside the body of a hen), foot disorders caused by the slanted wire floors of most battery cages, and Fatty Liver Hemorrhagic Syndrome. Because a large amount of calcium goes into egg production, almost all battery hens suffer from osteoporosis, which is exacerbated by lack of exercise in cages.
At the end of their laying cycle, most hens in U.S. egg factory farms are "forced molted," or purposefully starved for 10 to 14 days, to induce another laying cycle. Forced molting can double the mortality of a flock and is believed to cause significant suffering among birds. After the second laying cycle, battery hens are gathered and transported to slaughter plants. At the plants, the hens are shackled by their legs and hung upside-down on a long conveyer belt. Shackling often breaks the hens' fragile bones; by the time of slaughter, close to half of the birds have suffered broken bones. The hens are then submerged into an electrified water bath, which is supposed to render them unconscious, but many birds have their throats slit while fully conscious. Birds are not protected by the federal Humane Methods of Slaughter Act and are thus not required to be unconscious before being killed.
Standard industry practices cause battery hens to experience both acute and chronic pain. The treatment of these animals would be illegal if anti-cruelty laws applied to farmed animals. But, profits have taken priority over animal welfare.