A note on aggression and cannibalism in laying hens following re-housing and re-grouping

We examined effects of being moved and mixed with strangers on the incidence of aggression and cannibalism in caged White Leghorn hens with intact beaks. We predicted that mixing of strangers would increase rates of aggression and cannibalism. Hens were reared in 16 stable groups of four birds together since hatch. At 18 months of age, eight groups were moved intact to new cages (unmixed). The remaining hens were moved to new cages and combined into eight new groups of four unfamiliar hens (mixed). Data on aggression and cannibalism were collected during the 7 months before and after mixing. Aggression was higher in mixed than unmixed groups during the first week after mixing. By contrast. the frequency of aggression in unmixed groups was depressed on the day of moving but returned to pre-moving levels within I week. Contrary to our prediction, mixing with strangers had no effect on cannibalism. However, the incidence of cannibalism was altered during the first month after moving hens to new cages, being higher than pre-moving levels for injuries to the head and neck and lower for injuries to other body parts. (C) 2002 Elsevier Science B.V. All rights reserved.