Abstract

This thesis is based on the evidence of the use of range by laying hens from two
separate studies that were carried out on commercial flocks. The first study
involved a direct observation of 6 flocks of laying hens whereas the second study
was carried out on a single flock of laying hens using a still digital camera.
Mapping of the outdoor range into three zones, namely; apron (0-10metres),
enriched (10-50metres) and range (beyond 50metres), was carried out in both
studies determine whether it influenced the distribution, behaviour, nearest
neighbour distance (NND) and feather condition of the hens.
Based on the estimates of the total number of hens recorded outdoors, it was found
that 14.5% of the hens used the range in the first study, with 6.0% of the hens seen
in the apron, 4.8% in the enriched and the remaining 3.7% in the outer range zone.
This ranging pattern was further confirmed by the quadrat head counts, where the
hens used the apron most but showed a significant decrease in the use of other
outdoor zones as distance increased from the shed (p < 0.001). The results of the
two studies showed that range use peaked in the morning and decreased
significantly in the afternoon (p < 0.001). Range use was found to increase
significantly with age (p < 0.001) in the first study, although there was a significant
decrease in the number of hens outside the shed as the flocks got larger (p < 0.001).
The age effect reported in the six-flock study was complemented by the significant
positive effect of the week of outdoor access on the ability of the hens to use the
range (p < 0.001) in the single flock study. Range use increased as outdoor
temperature rose in the six-flock study whereas increased outdoor temperature
resulted in a decline in range use in the single flock study. NND of the hens was
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measured in the six-flock study and was found to decrease significantly towards
the shed (p < 0.001) and as the hens aged (p < 0.001). There was evidence that the
use of distant and less crowded outdoor locations by the hens in the first study
was associated with improved feather conditions.
The evidence presented in the two studies presented in this thesis showed that the
hens were unevenly distributed in the range, with reduced hen density (hen/m2)
towards the outer range and that an improvement in the use of distant parts of the
range may have beneficial effects on the hens.