A literature search was carried out for papers which described the intermittent lighting of laying hens and included information on mortality and behavioural responses. A review of 36 sets of mortality data indicated that intermittent lighting generally improved bird liveability, compared with that under conventional lighting. Biomittent lighting, which involved low total daily amounts of illumination, gave the greatest improvement. This brings into question welfare recommendations for a minimum of 8 h illumination per 24-h cycle. Asymmetrical and Biomittent intermittent lighting generally reduced vices, obesity and heat stress. Hens submitted to asymmetrical and Biomittent intermittent lighting had similar endocrine periodicities and patterns of activity to conventionally illuminated birds.
