Of course. But if you're asking whether you SHOULD do this, the answer is NO. Because of the difference in size between the stallion and the mare, there is a considerable risk of a serious birth issue in the baby. It's called feto-cephalic disproportion, and it happens in horses as well as in certain other species, such as elephants and giraffe. What it means is that foal is too large for the mare's body to deliver safely. In such cases, usually a C-section is the only answer- and if that cannot be performed, both the mare and foal are at risk of death. Do you really want to RISK that happening?