Influence of pop hole dimensions on the number of laying hens outside on the range.

The aim was to evaluate whether pop hole width is a factor influencing the number of laying hens on the range. Eight groups of 256 birds each were kept in 8 compartments in a deep litter system. Hens could leave each compartment through two equally-sized pop holes arranged evenly along the side of each compartment. Pop hole dimensions were varied every second week in each compartment in a random order from 30, 60, 90, 120 up to 150 x 30 cm (width x height). Range per hen (10 m(2)) were provided. The number of laying hens on range was counted hourly from 07:00 to 20:00 h. Pop hole width did not significantly influence the number of laying hens on the range. Our findings show that, within the limits of the dimensions investigated, other factors are more important than pop hole dimensions.