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.

Prolactin in the Horse: Historical Perspective, Actions and Reactions, and Its Role in Reproduction

“…Burkhardt [86] was the first to describe the use of indoor lighting to stimulate the ovaries of seasonally anovulatory pony mares during the winter. He mentioned in that report that the lighted mares actually began to shed their winter coat, although the outdoor temperatures they were exposed to during the day were very cold.…”

Fundamental Studies of the Reproductive Biology of the Endangered Persian Onager (Equus hemionus onager) Result in First Wild Equid Offspring from Artificial Insemination1

“…In contrast, female zebras living in zoos or the wild cycle and give birth year round [48]. Seasonality in the domestic horse is largely controlled by day length (extended daylight advances breeding season onset [49]), although genetics [50] and availability of food resources [51,52] also are influential. Our onager population always was exposed to adequate dietary needs yet still tended to cycle more during seasons of longest day length.…”

Control of the oestrous cycle of the mare

“…In breeds in which ovarian inactivity occurs only Burkhardt (1947) all authors have used a photoperiod of 16 h/24 h after a pro¬ gressive (Loy, 1968 ;Oxender, Noden & Hafs, 1977) or an abrupt . Little is known about the mode of action of light on the mare.…”