Effect of cage height and area on the behaviour of hens housed in battery cages.

Medium hybrid hens were housed as pairs and observed at three cage heights: 30.0, 42.5 and 55.0 cm, and at three area allowances per bird: 570, 807 and 1045 cm2. With increased height, head stretching, head scratching and body shaking were performed at a higher rate and feeding and cage pecking at a lower rate. There was also an increase in the time spent sitting. With increased area, head scratching, body shaking and feather raising were performed at a higher rate and cage pecking at a lower rate. It is concluded that spatial restriction may increase the cost of performing certain 'comfort' activities, resulting in the reductions in performance rate observed in the above experiments. Welfare implications are briefly discussed and considered to depend on the motivational state of the birds.