My 4 mares are all pretty well mannered when they are in heat. They become slightly cranky and you can tell they are a little more irritable, but have never had any of mine become crazy. The biggest problem I have is with my mustang mare, when she is in heat she has to stop and pee right in front of my mini stallion's stall and it takes an act of congress to get her to walk after she starts doing this. She just will not get it in her head he is to short to even try!
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"