Laying hens in large necks in a perchery system: influence of stocking density on location, use of resources and behaviour

1. ISA Brown laying hens (3000) were housed in a perchery in 10 pens, each with 300 birds. The pens varied in size to produce 4 different stocking den sities: 9.9 birds/m(2) (n=3), 13.5/m(2) (n=2), 16.0/m(2) (n=2) and 19.0/m(2 ) (n=3). Observations began at 20 weeks of age and continued until 69 weeks to establish the spatial distribution of the birds, usage of the different resources and the expression of behaviour. 2. Overall, birds spent most time on the perch frame (47%), litter area (23 %), slatted floor (17%) and nestbox area (9%). 3. There was no effect of density on the proportion of birds observed on th e slatted floor or on the elevated perches but as density increased the pro portion on the littered area decreased. 4. Space usage was determined vertically, horizontally and longitudinally I ndividual birds were seen to use about 80% of the pen volume available to t hem. This value was similar for all densities and showed that individuals d id not have separate home ranges. 5. Fewer vertical movements were made within the main perch frame at the up per than at the lower levels but movements between the perches of the main frame and the nestbox rails were relatively frequent. This may help birds m ove up and down through the main frame. 6. Behaviours which decreased in incidence with crowding included moving, f oraging and dust-bathing. Behaviours which increased with crowding included standing. Behaviours which were unaffected included resting, preening, pre laying behaviour, comfort behaviour and the minor behaviours. 7. The proportion of birds engaged in feeding and drinking was unaffected b y density, except each time the chain feeders (which operated intermittentl y) ran more hens were seen feeding at the lower densities. This suggests th at food delivery stimulated feeding behaviour; there may have been some res triction at the higher densities on birds feeding when and where they wante d. 8. Stocking density had no effect on the frequency of agonistic interaction s: threats, lunges, comb/head pecks, chases and fights. 9. The incidence of damaging pecking was low and not density dependent. 10. Increasing density within the range investigated inhibited the expressi on of a number of behaviours and limited the use of specific resources: bir d welfare at 19 birds/m(2) may have been very slightly impaired.