RELATION BETWEEN LIGHT-DARK RHYTHMS AND HOUR OF LAY OF EGGS EXPERIMENTALLY RETAINED IN THE HEN

Abstract

The ruptured follicle and all rapidly growing preovulatory follicles were removed from each of 48 hens. Twenty-one were then replaced under standard lighting (lights from 6:00 A.M. to 8:00 P.M) and 27 under reversed lighting (lights from 4:00 P.M.-6.-00 A.M.), and observed for hr. of lay. All except 4 birds retained their eggs, the majority of eggs in both groups being laid within 9-36 hrs. after the expected normal time. Seventeen of the retained eggs in each of the 2 groups were laid during lighted hrs., the most frequent hrs. of lay in both groups occurring at 7-10 hrs. after the onset of light. Seventeen of 19 birds operated on similarly, but with the ruptured follicle left intact, laid their eggs at practically the normally expected time, under either the standard (6 birds) or reversed (13 birds) lighting. An extraovarian, light-sensitive agent is evidently involved in the process of lay.