Using lights with horses allows for earlier heat with ovulation and a longer breeding season for better management of problem mares. The equine estrous cycle is the most variable in length of all domestic animals. During the summer months, the cycle averages 21 days in length. C. Parts of the estrous cycle in the mare. The mare is sexually receptive, peaking at ovulation.
Ovulation is the process where the mature egg is released from the ovary.
While the average mare ovulates two days before estrus, the range is from four days before to one day after the end of estrus. This is bad since the result of the breeding may be twins. Thoroughbreds and warmbloods tend to have more double ovulations. Certain mares double ovulate more than others and the frequency of double ovulations in a mare increases with age. Twin pregnancies in the mare aren't desirable due to abortions, etc.