Question: May not be a training problem, but I thought I would try anyway, since not getting much info from our vet.  Our stallion is agressive toward this mare, he has bred 10 other mares without probs, some outside mares.  She was also run off by another stallion prior to us buying her.  Is there anything we can do to get the stallion to accept this mare?  Thanks   Any help or insights much appreciated.

First, I have an observation that may shed some light on why this is happening with this mare. Stallions tend to like mares that were like their dams or other mares that were in their natal bunch, and not like those that do not look like their dam or the mares that they were in with as a foal.. 

So, some stallions will refuse to breed palomino, gray or mares with a lot of white on them, and/or act aggressively toward them, if the stallion's dam was a dark mare, or they were not exposed to a light colored mare as a colt. I would imagine that a curly coated horse would be a real strange sight to a non-curly horse, and that could very well explain the stallions' aggressiveness toward the mare. They don't really know she's a horse,  she
is too "weird" for them to readily accept as a horse, so they react by trying to drive her off.

I will tell you what I have done to get horses used to donkeys and mules, who horses also often react to the way your stallion is reacting to this mare, with fear and/or aggressiveness, and an effort to drive them away. They, too, are like horses enough that a horse knows it is some kind of equine, but is strange to a horse, in that they are often afraid of those
long ears and especially that insane (to a horse) sounding bray that donkeys and mules have in common. Mules sometimes make things worse because they often want to cozy right up to the horse, after all, the mule's mom was a mare, but the horse is freaking out because that critter just don't look, smell, or sound right!

Along this line, you may or may not be aware that, in order to get a donkey jack that as an adult will mate with mares, the very young jack foal has to be kept in with horses, so that he will accept breeding mares of a species other than his own when he is an adult. A jack that is kept in with other donkeys or by himself until an adult usually will not be willing to breed mares. This is how nature keeps species from interbreeding and either not
producing offspring at all, or producing usually (although not always) sterile offspring like mules.

I would put her in a pen secure from the stallion, but next to him. At first I would to set it up so that they couldn't even touch noses, but he could see and hear her and smell her scent carried to him on the air. You may see him doing the flemen reaction with the outstretched upper lip, using the very sensitive scent organs under there, to get used to her smell, and categorize it somewhere in his head that this really is a horse and not some
weird apparition as she apparently appears to him, and better yet, this really is a mare with whom there are breeding possibilities, if he can just get over that hairdo! Then as he seems to be getting more accepting of her, set it up so that they can touch noses and otherwise interact by touch and smell, but she could still get away from him so he can't injure her with
bites and kicks. Over a few weeks, he should get accustomed to her to the point that he would accept her, and you could put her in with him. This has worked for me to accustom horses to mules and donkeys, and even cattle with one mare I had one time that was initially terrified of them. 

Annette
 

From Panelists Laura

Stallions can become picky about the mares they breed if she is a color they 
don't like.  I don't know if it is the hair coat that turns your guy off or 
if she has a different odor than the other mares he has bred.  A couple of 
things you might try: 1. Bait & Switch - Put a mare that you know he likes 
(who is also in season) next to the mare you want to breed, as he comes up to 
mount, direct him onto the Curly mare.  2.  Use artificial insemination.  If 
your stallion is getting aggressive towards your mare, I would recommend the 
artificial insemination - you don't want anyone to get hurt.
Laura