Ontogeny of behaviour in intact and beak trimmed layer pullets, with special reference to preening.

1. The effects of commercial beak trimming on layer pullet behaviour were investigated, with special reference to preening. 2. One-d-old chicks, 96 in all, were housed in 12 litter floor pens, with 8 birds in each, to 20 weeks of age. Approximately one quarter of the beak was trimmed in all birds in half of the pens (BT) at 8 d of age using a hot blade debeaker. The birds in the other pens remained intact (NBT). 3. There was no significant effect of beak trimming on body weight at any age. At the end of the study, upper mandible lengths were shorter in BT birds. 4. Beak trimming had very little effect on behaviour. NBT birds showed more litter-directed behaviour than did BT birds, and BT birds spent more time in preening directed at the preen gland, and at the back while sitting. 5. Feather damage was minimal and there was no difference in mean feather damage scores between treatments at any age. 6. The young age and small amount of beak removed during beak trimming may be at least partly responsible for the lack of effects of beak treatment on behaviour and plumage condition.