Question: My miniature stallion will not accept new mare introduced to the herd of 12 mares. How long should I allow abuse to continue. The stallion will run this little mare away from his herd of mares. He not only chases her, he bites her face, and her tail. I realize that they he may be letting her know that he is the guy in charge, but there is injury to her face, butt, and tail to a pointof bleeding and infection.After this went on for 2 weeks, I separated the new mare from the herd, let herrun with the mares for three days, then let the stallion back into the herd. Itstarted all over again. Next, I separated her again but let two of the maresbond with her thinking that would help. Again, when she and her two mares shewas with entered back into the herd, the stallion started all over again. Hehas had other new mares introduced to him in the past (usually 2-3 at a time)and the adjustment did not take more than a few days, never with suchaggressive behavior as being displayed now. Help! It is possible that he seesthis little mare (very passive) as a threat to his herd? Should I justpermanently keep her away from this stallion?

Answer: Altering behaviors in a herd pasture situation is often very difficult. Several factors may be influencing your stallion’s behavior. The number one cause of aggression in pasture herds that I’ve seen have been due to lack of space, or overpopulation of the pasture. In the wild, stallions are sometimes extremely aggressive toward a particular mare. In these situations, that mare would generally be driven away from the herd. In domestic situations, this is not possible and leads to continual aggression toward the mare that would be ousted. Aggression has been documented as increasing in frequency in "confined" spaces during all sorts of social interaction among horses, from feeding to pasture breeding. A confined space can be even a sizable pasture, depending on the number of horses. Remember, even though you are raising minis, they usually require nearly as much pasture space as larger horses in a mixed sex pasture breeding operation.

I highly doubt the stallion sees your new mare as a threat to his herd, but probably sees her as incompatible to his herd for another reason. If the mare is too young to be breeding age, he may be rejecting her for this reason. If she is already in foal, your stallion may not accept her. If your dominant "boss" mare doesn’t accept your new horse, your stallion may not either. If the new mare is closely related to the stallion, he may reject her as a member to his harem. In summary, there are many reasons why your new mare may not be accepted by the stallion. Some horses simply do not get along and cannot be pastured together. If you have purchased this mare specifically to be part of your breeding program, I can only suggest that you pasture your new mare separately from your stallion and hand breed them. He may refuse to breed the mare, but this is rather rare if the mare is in standing heat (stands for breeding and shows expected behaviors of estrus). If you are inexperienced at hand breeding or your stallion has never been hand bred, you might seek the assistance of your veterinarian or another experienced and trustworthy local source. Good luck and keep the safety of all concerned in mind!