Mares are seasonally polyestrus; this means that they experience regular estrus cycles during late Spring, Summer and early Fall, with none occurring during the Winter. The typical mare cycles regularly between March and October, with each estrou …

Gonadotrophin-releasing hormone (GnRH) is a hormone produced by the hypothalamus in response to an increase in day length. As the hours of daily sunlight (or photoperiod) increase, melatonin levels subside, allowing GnRH to be produced. Productio …