Time of follicular transformation to the rapid growth phase in relation to the ovulatory cycle of laying hens.

To demonstrate time of transformation of ovarian follicles from the resting stage to the rapid growth phase, Sudan black in ethanol was intravenously injected into laying hens, and 4 hr later Sudan red in water was injected into the same hens; the hens were killed 4 hr after the last injection for observation of the follicles. Injections were made at various times during an ovulatory cycle. In an additional experiment, hourly yolk deposition in the dark period (1900 to 0500 hr) was compared with that in the light period. Follicular transformation occurred at a high frequency within the period of 8 to 14 hr after ovulation. This period corresponded to the time between 1700 and 2400 hr. Hourly yolk deposition in the dark period was higher than that in the light period.