Rhythm of Lay in Chickens as Influenced By a 16 Hour “Day”

LENGTH of the natural daylight or of imposed periods of artificial light restrict the pattern of lay of most domestic fowls. Egg sequences are usually initiated in the early morning and terminated in mid or late afternoon. Continuous alternating periods of light and dark fail to alter the rhythmic 24-to-26 hour laying pattern of the hen. Thus, the nature of the neurohumoral control of lay with regard to the role of the dark and of the light period of the day can best be tested under periods of unusual or abnormal day lengths and photoperiods. The purpose of these experiments was: (1) to attempt to modify the time interval between intra-sequence eggs by imposing an unnatural day length of 16 hours (8L-8D), and (2) to examine the extent to which darkness and the normal daily activity period influence the initiation and termination of egg sequences. METHODS AND PROCEDURE The hens …