Behavioural time budgets of broiler chickens reared in varying light intensities

Light management is a critical component of production for intensively housed animals. To increase productivity, broiler chickens are often raised commercially in houses that are dimly illuminated on a near-continuous basis. There have been relatively few studies examining the effects of light intensity on the behaviour of broilers. We evaluated the time budgets of broilers (N = 464) housed under one of three photophase light levels (5, 50 or 200 lx) chosen to produce low, moderate or high illumination contrasts with the scotophase light level (1 lx). There were four replicate pens of broilers per treatment. We recorded behaviour for 48 continuous hours during weeks 3, 4, and 5 of age and analysed the time broilers spent exhibiting eight behaviours and two behavioural categories (inactive and active) during the overall photoperiod, photophase and scotophase. There were only two main effects of light intensity on behaviour during the overall photoperiod: 5 lx broilers preened and foraged less than the 50 (P = 0.03, P = 0.03, respectively) and 200 lx birds (P < 0.0001, P = 0.009, respectively). Light intensity did, however, affect the distribution of behaviour over the photoperiod. The 5 lx broilers spent more time sleeping (P = 0.04, both comparisons) and less time preening (P < 0.0001, both comparisons) and foraging (P = 0.0006, P = 0.0003) than broilers in the 50 and 200 lx treatments, respectively. During the scotophase, however, they spent more time performing active behaviours such as eating (P < 0.0001, both comparisons), walking (P < 0.004, P < 0.001) and foraging (P < 0.002, P < 0.0003) than the 50 and 200 lx treatments, respectively. These findings suggest that low contrast between the photophase and scotophase in the 5 lx group produced a more even distribution of behaviours over the photoperiod. We conclude that the intensity of light influences the time budgets and activity patterns of broilers, and discuss the potential welfare benefits of housing broiler chickens in a lighting environment that provides greater day–night illumination contrast than is typical for commercial broiler production.