Effect of intermittent lighting on performance and energy metabolism of broilers.

The effects of an intermittent light scheme (IL) with cycles of 1 hr light and 3 hr of darkness, vs. 23 hr light and 1 hr darkness or continuous light (CL) on performance and physiological parameters from 1 week until 6 weeks of age were tested in an experiment with 960 broilers in two respiration chambers. The IL group tended to grow faster (2.1 g per bird per day) and to consume more feed (1.6 g per bird per day). The ratio of feed intake to weight gain (feed conversion) however, was consistently lower; in the first 2 weeks of the experiment it was significantly lower. Percentage of abdominal fat of IL birds was 2.93 compared to 2.67% for the CL birds. Incidence of leg abnormalities was 6% in the IL and 11% in the CL group. The tendency to a higher efficiency of the IL group may be explained by a lower heat production (H) in this group in 4 out of 5 experimental weeks. Values of H were 786 kJ per kg.75 per day for the IL group, 817 kJ for the CL group (4.184 kJ/kcal). The calculated energy requirement for maintenance was also lower in the IL group than in the CL group: (458 kJ and 486 kJ per kg.75 per day, respectively.) This difference may be associated with less activity of the IL group compared with the CL group.