Reproductive Cycle
Mares carry their young, called foals, for approximately 11 months from conception to birth. (Average range 320–370 days.) Usually just one young is born; twins are rare. When a domesticated mare foals, she nurses the foal for at least four to six months before it is weaned, though mares in the wild may allow a foal to nurse for up to a year.
The estrous cycle, also known as "season" or "heat" of a mare occurs roughly every 19–22 days and occurs from early spring into autumn. As the days shorten, most mares enter an anestrus period during the winter and thus do not cycle in this period. The reproductive cycle in a mare is controlled by the photoperiod (length of the day), the cycle first triggered when the days begin to lengthen. As the days shorten, the mare returns to the anestrus period when she is not sexually receptive. Anestrus prevents the mare from conceiving in the winter months, as that would result in her foaling during the harshest part of the year, a time when it would be most difficult for the foal to survive.
However, for most competitive purposes, foals are given an official "birthday" of January 1 (August 1 in the Southern hemisphere), and many breeders want foals to be born as early in the year as possible. Therefore, many breeding farms begin to put mares "under lights" in late winter in order to bring them out of anestrus early and allow conception to occur in February or March. One exception to this general rule is the field of endurance riding, which requires horses to be 60 true calendar months old (5 years) before competing at longer distances.
Fillies are sexually mature by age two and are sometimes bred at that age, but generally should not be bred until they themselves have stopped growing, usually by age four or five.
A healthy, well-managed mare can produce a foal every year into her twenties, though not all breeders will breed a mare every year. In addition, many mares are kept for riding and so are not bred annually, as a mare in late pregnancy or nursing a foal is not able to perform at as athletic a standard as one who is neither pregnant nor lactating. In addition, some mares become anxious when separated from their foals, even temporarily, and thus are difficult to manage under saddle until their foals are weaned.
Read more about this topic: Mareš
Famous quotes related to reproductive cycle:
“In the nineteenth century ... explanations of who and what women were focused primarily on reproductive events—marriage, children, the empty nest, menopause. You could explain what was happening in a woman’s life, it was believed, if you knew where she was in this reproductive cycle.”
—Grace Baruch (20th century)