Monitoring broiler behaviour is a helpful tool in assessing the impact that management
systems, such as lighting programs, have on bird welfare. This study examined broiler
behaviour at two ages in two separate flocks (27/28 days of age (27d) in flock one and
42/43d (42d) of age in the second flock) as affected by one of four lighting programs:
14Light (L):10Dark (D) (14L), 17L:7D (17L), 20L:4D (20L) and 23L:1D (23L). These lighting
programs were chosen so relationships between the percentage of time spent on particular
behaviours and daylength could be examined using regression analyses. Data were
recorded with an infrared camera system, and then observed using a scan sample technique.
The number of birds performing particular behaviours was recorded every 10 min
for a 24-hour (h) period (6 measurements×24-h per d) in two replicate pens per lighting
treatment per age. The data, as a percentage of time, were tested for normality, and
(log + one transformed) prior to analysis. Photoperiod length altered behaviour regardless
of age during both the photophase and when averaged over the 24-h period. A negative
linear or quadratic reduction in percent of time spent standing, walking, feeding, preening,
stretching, dustbathing and litter pecking was found with increasing daylength at both ages
in both the photoperiod and 24-h average. A similar reduction for running behaviour was
found in the photoperiod and 24-h period at 27d, with the behaviour eliminated under 23L.
Dustbathing was no longer present in the behavioural repertoire of the older 23L birds. Long
photoperiods resulted in a reduced reactivity of birds to the presence of an observer, and of
sound level within a room. Differences in percent of time spent performing all behaviours
were non-existent or minor in birds raised on 14L and 17L, and reactivity was similar at
27d, but higher in 14L birds at 42d. Sound levels within these rooms were similar. Birds
raised on 20L were intermediate in behavioural expression. In conclusion, the decrease
or elimination of behaviours, including those that are highly motivated or necessary for
health, indicated poor welfare for birds raised on near-constant light. There appeared to be
no behavioural advantages for the use of a long scotoperiod such as in the 14L:10D program
as compared to a 17L:7D program. Based on behavioural expression, optimal welfare was
achieved under 16L to 17L.