Many hens eventually lose all their back feathers as these are easy targets for other birds. As birds are unable to escape one another, feather-pecking can escalate into increased aggression and cannibalism. This involves cutting off about one-third of the bill using a heated blade without anaesthetic. This is obviously very painful for the birds and studies have shown that the pain lasts for a prolonged period if not indefinitely. Birds may not resume normal pecking or preening for as long as six weeks after debeaking, and in some cases profuse bleeding and death from shock occurs.
Caged hens have no nesting material and no quiet, dark place in which to lay.
Hens become frustrated and aggressive prior to lay and may attempt to hold back egg-laying. Unchecked growth of claws is another problem faced by battery hens. Normally their claws would be worn down by walking and scratching. This is not possible in battery cages and so claws may grow and become entangled in the wire floor. This can prevent birds from reaching food and water, causing death from hunger or thirst.