Relationship between hen age, body weight, laying rate, egg weight and rearing system

weeks of age. Hens (150 S and 150 H) were assigned to 10 replications of 15 birds and kept on litter at a stocking density of 4.2 birds/m2. The remaining 152 hens were allocated to 4 replications of 28 birds and placed in a 3-tier battery of individual cages at a stocking density of 1150 hens/m2. The following parameters were evaluated during the experiment: body weight, egg production, mean weight of eggs laid, daily feed intake per layer, and health status. The mortality of H and S hens kept on litter was high (13 % and 18%) compared to that of birds in cages, which was 9.6 % and 3.1%, respectively. The aggression in hens kept on litter in the initial period of egg production increased the number of eggs laid outside nests. H hens were later to go into egg production, and production was relatively low (63.4%). Caged S layers showed a significantly (P<0.05) higher laying rate (82.4%) than H hens kept on litter (69.6%). The weight of H hens kept in both systems increased by approx. 1000 g on average in relation to the weight at 20 weeks of age, while the weight of lighter S layers increased by just 500 g. In H and S hens, a relationship was found between egg weight and layer age, with heavier eggs being laid by caged H layers than by caged S layers. The mean egg weight during the whole experimental period was similar in all the groups. The housing system had a statisticall