Understanding the Mare's Transitional Period
Nature has timed the mare’s breeding season to maximize her foal’s chances of survival during winter. This evolution has led the mare to be a long-day, seasonally polyestrous (meaning her estrous cycles depend on the season) animal whose regular ovulatory cycles occur in response to increasing day length. During winter, or increased periods of darkness, the small pineal gland in the brain releases the hormone melatonin, which plays a pivotal role in seasonality of reproduction. The exact mechanism by which melatonin acts, however, is unclear.

At the same time, the mare’s hypothalamic-p

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