It is estimated that more than 60 percent of the world’s eggs are produced in industrial systems, mostly using barren battery cages.
While barren battery cages were banned in the EU in 2012, 95 percent of US layers remain confined within them. Each battery cage houses up to 10 birds. The average space allowance per bird in a typical battery cage is less than a letter-size sheet of paper, and the height is just enough to allow the hen to stand.
The cages usually have a sloping wire mesh floor and are kept in rows stacked in several tiers. Each shed typically houses tens of thousands of hens this way, and the largest sheds can contain more than a hundred thousand birds. Typically these buildings are artificially lit and ventilated.
Caged hens may never experience natural light or fresh air and do not leave their cages until they are gathered for slaughter.
While enriched cages provide more space than battery cages and can allow hens to express more of their natural behaviors, such as perching, dustbathing, and nesting, they are still very restrictive. Hens cannot fly up to a high perch to be safe from feather pecking, the litter area is often very limited, and effective dust bathing generally is not possible.
In the US, barren battery cages remain legal in most states, and the majority of eggs are produced using battery cage systems.
Although the battery cage was banned in the EU, the use of “enriched” cages remains legal there. The original enriched cages housed 10 hens, but most recent systems in the EU are colony cages housing 60 to 80 hens. Colony cages are slightly less crowded (space per hen is approximately 20 percent larger than a letter-size piece of paper) and the hens have a small area in which they are able to move around. Nest boxes, litter, perch space, and “claw shortening devices” must be provided.
Modern commercial hens have been bred to produce large numbers of eggs. This depletes the hen’s store of calcium and can result in high levels of osteoporosis (brittle bones) and fractures. Restricted movement can also contribute to osteoporosis.
Several tiers of crowded cages make inspection difficult, and in large cage sheds injured birds are often left to die unnoticed.
Hens often lose a large proportion of their feathers due to damage from the sides of the cage and pecking from other hens. To prevent feather pecking, chicks often have part of their beaks cut off without anesthetic. While beak trimming with a blade became illegal in the UK in 2011, this technique, along with beak trimming with a specialized infrared light, remains legal in the US. Infrared beak trimming may be less painful than blade trimming, although blade trimming is more common.
Even though it is often claimed that confined animals are better protected from infection, a survey by the European Food Safety Authority found that eggs produced in cages are more likely to be contaminated with Salmonella than those produced in cage-free systems.
There are alternative methods of egg production that do not require the hen to endure the suffering of cages.