When Will My Horse Be In Season?

Is it possible for a mare to come into season in the winter? I know it is unusual but she is turned out with a stallion like gelding and she is showing signs of coming into season. (Sammy Jo Priest - United Kingdom)

Like sheep and goats, mares are seasonal breeders. Sheep and goats are short-day breeders that begin to ovulate (release the egg from the ovary) in the fall in response to decreasing day-length. Mares, on the other hand, enter their ovulatory or natural breeding season in the spring in response to increasing day-length. From the standpoint of fertility, the ideal time to breed mares in the Northern Hemisphere is from May through August.

Because sometimes it is beneficial to have the mare mated earlier in the year, there are accepted practices for inducing ovulation in the mare early. The most common approach to early breeding is to place the mare under supplemental light starting in late November or early December. Essentially, you must convince your mare that spring has arrived by exposing her to artificially increased day-length. Light can be supplemented in the afternoon and evening to give a total of 16 hours light each day. Most mares will begin ovulatory cycles after about 60 days of light supplementation and will be ready to breed in February and March.

So it does seem unlikely that in a mid northern hemisphere country a mare can be ovulating so early in spring without intentional interference. However, there are always unusual cases - every animal is different - and since your horse is also a Welsh Pony, they may be more prone to early ovulation than breeds that originate in more southern climates.

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