Hundreds of millions of chickens in the egg industry suffer from poor welfare throughout their lives. Male chicks, considered a byproduct of commercial hatcheries, are killed soon after they hatch. The females are typically beak-trimmed, usually with a hot blade, to prevent them from developing the abnormal pecking behaviors that manifest in substandard environments. The overwhelming majority of hens are then confined in barren battery cages, enclosures so small that the birds are unable even to spread their wings without touching the cage sides or other hens. Battery cages prevent nearly all normal behavior, including nesting, perching, and dustbathing, all of which are critically important to the hen, as well as deny the birds normal movement to such an extent that the hens may suffer from physical ailments, including osteoporosis and reproductive and liver problems. Once their productivity wanes, typically after 1-2 years, the hens are “depopulated,” and many experience broken bones as they are removed from the cages. The birds are either killed by gassing on the farm or after long-distance transport to a slaughter plant, where they experience further stress and trauma associated with shackling, electrical water-bath stunning, and throat-cutting. Throughout the commercial egg industry, the welfare of birds is severely impaired.
The Humane Society of the United States, "The Welfare of Animals in the Egg Industry" (2008). IMPACTS ON FARM ANIMALS. 16.