Cannibalism is more common amongst intensively-housed birds not kept in cages. The small area allowance and low ceiling in battery cages are likely to cause discomfort. Discomfort can indicate uneasiness of the mind, as well as the body. In this regard, birds will experience discomfort when intensive housing conditions do not allow for 'personal space'. Increased population density causes birds to encroach into the personal space of others, which may result in stress, hysteria and social strife.
Birds can experience both stress and physical discomfort on capture and transportation.
They can be unused to human contact. Pre-slaughter handling can also cause discomfort, particularly the practice of shackling birds upside down on the slaughter line. It is done in both cage and floor housing systems. Skeletal weakness can be caused by high levels of egg production. Shackling upside down for slaughter will cause further injuries for birds with leg weaknesses.