Diurnal-nocturnal changes in food intake, gut storage of ingesta, food transit time and metabolism in growing broiler chickens: a model for temporal control of energy balance.

1. Diurnal-nocturnal changes in food intake, gut storage of ingesta, food transit time and heat production were studied in male broiler chickens reared under a 14L:10D lighting schedule (lights on from 06.00 to 20.00 h). 2. Food consumption during the scotophase was negligible. Peak food consumption during the photoperiod occurred at the beginning of the photoperiod and in the late afternoon. 3. During the photoperiod, the crop and proventriculus/gizzard contained only small quantities of ingesta. However, at the beginning of the scotoperiod, dried ingesta content of crop and proventriculus/gizzard increased by 10.5- and 2.76-fold respectively. This increase was followed by a gradual decrease towards the end of the scotoperiod. 4. Food transit time during the scotoperiod was significantly longer than that during the photoperiod. 5. The daily pattern of heat production closely followed the 14L:10D lighting schedule. Total heat production during darkness averaged 53% of total heat production during the photoperiod. 6. It was estimated that the storage of energy (as ingesta) in the crop and proventriculus/gizzard, followed by its gradual release and the increased food transit time during the night, contributed 75.5% of nocturnal energy needs. It must be recognised that these mechanisms play a major role in the energy balance of the growing chicken during periods without food intake.