The Effect of Continuous Light and Continuous Noise on Pullets Held in a Sealed Chamber

IT IS well known that hens, kept under normal environmental conditions, have a tendency to lay eggs mainly in the hours of daylight. There are, however, exceptions to this and we have observed birds which could be regarded as notorious ‘night layers.’ One pullet for example, out of a total of 14 eggs laid during the month of May in 1959, deposited seven between 8 p.m. and 5 a.m., a period of complete darkness. Admittedly, such a pattern of lay is rare. Warren and Scott (1936) showed that hens would lay at any hour of the day (24 hours) when placed under continuous artificial lighting. Only a short period of time (less than seven days) was necessary for the disruption of the normal rhythm. McNally (1946) made similar observations but Fraps, Neher and Rothchild (1947) were unable to induce their birds into a state of random lay with the…