Use of pen space and activity of broiler chickens reared at two different densities

A better understanding of the motivation of broiler chickens reared indoors to go to and remain in a different part of the pen (or not) could help to provide appropriate organisation of the rearing space on farms. This study was performed to determine whether broiler chickens reared in large pens (9 m x 5 m) congregate in certain specific areas and if so, where they congregate. The existence of lying areas was researched. Two areas were distinguished: one contained drinkers and feeders (DF area) and the other was free of equipment (Free area). In the first experiment the distribution (in the Free and DF areas) of two groups of chickens reared at a density of 2 birds/m(2) was compared in two pens with similar equipment to verify that the distributions obtained in each pen were similar. In the second experiment, the distributions of two groups of chickens reared at a density of 2 chickens/m(2) and two groups reared at a density of 15 chickens/m(2) were compared. The behaviour of 16 individually marked chickens per group was also assessed. Observations were performed by scan sampling method from weeks 4 to 6. The presence of cutaneous dermatitis and valgus and varus deformities was recorded at the end of the rearing period (day 42). The results indicated that chickens at the higher density mainly stayed and lay in the Free area. At the low density they preferred to stay and lie near drinkers and feeders and had limited use of the Free area. The presence of a large amount of available space in the Free area in the groups reared at 2 chickens/m(2) had no influence on the behaviours performed in this area as the frequencies of these behaviours were similar to those observed in the groups reared at 15 chickens/m(2). The rearing density had a clear influence on the occurrence of foot pad and hock dermatitis but not on the occurrence of varus and valgus deformities. These results show that chickens spontaneously limited their physical effort and only rarely went to some parts of the pen when reared at low density. These results emphasise the need to find situations that could stimulate activities to avoid local densities that could have deleterious effects on health and comfort. (C) 2003 Elsevier B.V. All rights reserved.