The effect of ahemeral light and dark cycles on patterns of food intake by the laying hen

Abstract
1. Diurnal food intake rhythms of laying hens were studied under 21, 24 and 30‐h cycles, using either a constant 12‐h photoperiod or a 10‐h scotoperiod in each cycle. The feeding patterns essentially followed a circadian periodicity under all experimental situations. The peak in food intake which normally occurs before “sunset” in a 24‐h cycle was consistently observed to be timed from the onset of the previous dark period in each light and dark cycle, regardless of cycle length. 2. This study demonstrates that the laying fowl makes use of an endogenous biological rhythm to regulate its feeding behaviour. A light to dark transition in a light and dark cycle is the primary signal for phase‐setting the pattern of food intake.