Transition from anoestrus in the mare and the effects of artificial lighting

Abstract

1. The recommencement of the sexual rhythm from deep anoestrus, is described in barren pony mares. Follicular development and oestrus follow after an interval of preliminary changes in the ovaries and accessory reproductive organs.2. The onset of oestrus can be accelerated by general irradiation with strong artificial light. Local irradiation with a mercury vapour lamp has no effect on the ovaries.3. Pregnant matings will result from such artificially induced heat periods provided that ovulation is induced.4. Doses of less than 10 c.c. of sperm injected will cause fertilization when ovulation is so induced.5. There is a close connexion between the shedding of the coat and renewed ovarian activity.6. The stimulus to the ovaries probably passes through the eyes as in the ferret.