how long is a mare's estrous cycle
During those seasons the mare will have a heat cycle (estrous cycle) about once every 21-23 days and during that cycle, she will have from 3-8 days of standing heat (estrus, note the difference in spelling between the cycle and the standing heat) where she would be receptive to a stallion for breeding.uring those seasons the mare will have a heat cycle (estrous cycle) about once every 21-23 days and during that cycle, she will have from 3-8 days of standing heat (estrus, note the difference in spelling between the cycle and the standing heat) where she would be receptive to a stallion for breeding.