LIGHT AND THE CONTROL OF THE OESTROUS CYCLE IN THE FERRET

Abstract

SUMMARY The effect of exposure to long-day conditions, begun at different times during the summer and autumn, on the timing of oestrus in the ferret has been studied. When ferrets were transferred to 16 hr. days in July or August, oestrus set in very rapidly or was inhibited, but when ferrets were subjected to prolonged illumination later in the year, in October or November, a more typical response ensued in that the animals came into heat after about 6 weeks. Loss of hair, which proceeded to the development of bald areas, was observed after long exposure to 16 hr. light daily. The period of illumination was reduced from 16 to 8 hr. daily for seven animals which had failed to come into heat after extended exposure to long-day conditions. After 8 weeks, long days were re-imposed and oestrus rapidly ensued in six females. Marked growth of hair took place under short-day conditions. Exposure to short-day conditions from birth was compatible with a normal timing of oestrus in eight out of 12 females. It is concluded that under certain conditions prolonged illumination can inhibit the secretion of gonadotrophin in the ferret and block the manifestation of an inherent rhythm of sexual activity.