by Newberry et al. (1988). The expression of exploratory
and comfort behaviours has been found to be reduced with
exposure to dim light (5 lx; Alvino et al., 2009). Furthermore,
behaviours were evenly distributed over the 24 h
day/night period in broilers exposed to a light intensity
of 5 lx in contrast to birds exposed to 50 or 200 lx, which
demonstrated distinct behavioural day–night rhythms. The
lack of rhythms when light intensity was 5 lx during the
day was suggested by the authors to be a welfare consideration
as it might result in the interruption of normal
circadian rhythms of a flock. Possibly contributing to the
lack of rhythm was the use of 1 lx during the scotoperiod,
which may not have been sufficient contrast to 5 lx during
the day time period to induce a day–night behavioural
cycle.