Here's a super idea that works really well. I have been doing this at my farm for the past three (3) years. I use oxytocin (PIT) injections on all foaling mares beginning on day two post foaling. Of course we must use common sense in the matter. If your mare had a rough birthing or has a  tremendous amount of swelling around her vulva I would hold back an extra day or two. I have found that this really cleans up the uterus, assists the involution, giving you a jump start on the foal heat breeding.

It is always a good idea to speak to your veterinarian and get his/her thoughts and ideas on this matter. I also use Oxytocin one hour post breeding. On any mare, foaling, maiden or barren, this acts to clean out any debris leftover  from the insemination/live cover. Again, speak to your veterinarian about this matter. If you think about the action that Oxytocin causes it totally makes sense!