When do mares come back into heat after foaling?

Mares usually come back into heat about a week after giving birth.

However, they are usually less fertile than in their normal heat cycle. Some breeders do not attempt to breed mares back on their foal heat, especially as it has a higher rate of failure and there's some indication that pregnancy loss is more likely. In general, mares are bred back on the second heat after giving birth.

Some Thoroughbred breeders, though, like to breed on the foal heat to get an earlier foal.