The preferences of broiler and layer strains of fowl for four different int
ensities of incandescent luminaire (6, 20 60 and 200 lux; Osram, 60 W, pear
l) were tested at 2 and 6 weeks of age. With each strain, four replicates o
f 12 birds were each allowed to move freely between four compartments illum
inated continuously at the different intensities for 6 days. The distributi
on of light intensities among the compartments was changed daily. After 2 d
ays of conditioning, the birds' location and behaviour were recorded once e
very 15min over 23h on each of the remaining 4 days. The other hour was dev
oted to changing light intensities and refilling the feeders and drinkers.
Six, mutually exclusive behaviours were defined: resting, perching, feeding
, drinking litter-directed activity and locomotion.
With both strains, most time was spent in the brightest (200 lux) environme
nt at 2 weeks of age, but in the dimmest (6 lux) at 6 weeks. This apparent
change in preference was associated only with the two behaviours which rook
up most time, resting and perching, whereas the highest intensity was cons
istently preferred for all other behaviours. Older birds thus preferred to
be in dim light when they were relatively inactive.
The finding that older birds prefer to spend much of their time in a light
environment of < 10 lux intensity, depending on behaviour, is contrary to c
urrent recommendations that minimum light intensities for broilers and layi
ng hens should be increased to as much as 20 lux. Some variation in the spa
tial or temporal distribution of ambient light intensity, to provide both d
imly (< 10 lux) and brightly (eg > 50 lux) lit environments, might benefit
the welfare of older poultry, although further work is needed to establish
their optimal light environment.