Egg Laying and Ovarian Follicular Growth in Japanese Quail under Continuous Lighting.

Abstract

Egg laying and ovarian follicular growth pattern in Japanese quail were compared between the conditions of 14hr lighting and 10hr darkness (14L/10D) and of continuous lighting (LL). Laying quail at 15 weeks of age were maintained firstly under 14L/10D and secondly under LL for each 7 weeks. Their oviposition times were recorded throughout the experimental period. To examine the follicular growth pattern under the both conditions, three kinds of the fat soluble dye were orally given once a day at a fixed time for 7 weeks under each condition.Ovipositions under 14L/10D were concentrated within the period from 8hr after the onset of lighting to 2hr after the onset of darkness with a peak of 11 to 12hr after the onset of lighting. It was proved that ovipositions under 14L/10D showed a high entrainment to light-dark cycle. On the other hand, ovipositions under LL were found uniformly in all of the 24hr. The oviposition interval between intraclutch eggs was 24.70±0.07 (mean±S.E.M.) hr under 14L/10D and 26.83±0.05hr under LL. The interval lengthened significantly by transfer to LL. Quail under LL revealed a decrease of relatively short clutches with 1 to 6 eggs while an increase of long clutches of more than 10 eggs, comparing with those under 14L/10D.By transfer from 14L/10D to LL, length of the follicular rapid growth period and yolk volume at the time of ovulation increased significantly. However, no significant change was found on the number of growing follicles in the ovary and the total amount of daily yolk deposition under the both conditions. The results indicate that light-dark cycle consisting of the total of 24hr affects follicular growth period and follicular volume at the ovulation.