Factors affecting ranging behaviour in young and adult laying hens.

1. A study was conducted to investigate the effect of environment on ranging in 33 flocks reared with (16) or without (17) range access. Ranging was observed at 8, 16 and 35 weeks. Information on house layout, weather conditions and range characteristics was used to create models predicting the percentage of the flock out on the range and the percentage of ranging birds observed away from the house. 2. Three flocks had range access at 8 weeks. The percentage of birds ranging averaged 28%, with 22% of these ranging away from the house. For the 13 flocks with range access at 16 weeks, the percentage of pullets on the range was 12%, with 29% of these ranging away from the house. At 35 weeks, all flocks had range access and the average percentage of birds out on the range was 13%, with 42% of these ranging away from the house. 3. The percentage of birds seen using the range was higher with reduced flock size and stocking density, increased pop hole availability (cm/bird) and light intensity inside the house. More birds ranged on cooler days and on farms located in areas with fewer days of rain per year and lower average rainfall. The percentage of birds ranging varied with season and was lowest in May. More birds ranged away from the house when cover and more artificial structures were present on the range. The proportion of ranging birds located away from the house increased with lower outdoor humidity levels, higher air pressure, and on warmer days. Lastly, birds ranged away from the house more as they got older.