Responsiveness to a novel preening stimulus long after partial beak amputation (beak trimming) in laying hens

Thirty beak-trimmed and thirty intact hens were reared in mixed groups and individually housed in battery cages; partial beak amputation took place 6 weeks after hatching. All hens were tested with a novel stimulus when they were 42 weeks old: a small paper sticker (36 mm(2)) was attached to the distal parts of the feathers at the back of the hen. It took beak-trimmed hens on average 27 seconds and the intact ones 8 s to start preening the sticker. This difference was statistically significant. Beak-trimmed hens tended to preen the sticker less than intact birds. Lighting conditions had no effect on the response latency, while the amount of eating and drinking did not differ between both groups, indicating that lack of light, anxiety or other types of disturbances did not affect the preening responses. It is concluded that beak trimming has long lasting consequences in reducing the responsiveness to a novel preening stimulus. This result is in agreement with the long term passivity in beak-trimmed hens found in other studies. The development of a reduced responsiveness as a result of beak trimming suggests poor animal welfare.