Effect of four lighting regimes on broiler performance, leg abnormalities and plasma corticoid levels.

The effect of four lighting regimes: (1) continuous light (5 to 10 lux); (2) an intermittent system of 1 hr. of light (5 to 10 lux) and 3 hr. of darkness; (3) an intermittent system of 1 hr. of light (5 to 10 lux) and 3 hr. of darkness interrupted by 13 hr. of regular light (5 to 10 lux); (4) as with (3) but with low intensity light (less than 1 lux) during the 13 hr. period while the intermittent system continued, was studied in 2400 broilers of two commercial crosses over two trials. Lighting regime had a significant effect of body weight in trial 2 with birds on treatments 3 and 4 being lighter than those on treatments 1 and 2 which did not differ. Lighting regime had no significant effect on feed to gain ratio, percent crooked toes or mortality to 8 weeks. Birds grown on continuous light had significantly more leg abnormalities than those grown on any of the intermittent regimes. In trial 1 birds grown on continuous light had significantly higher plasma corticoid levels than those grown on any of the intermittent regimes. The same trend existed in trial 2, except that birds on treatment 3 had the highest plasma corticoid level.