I bought a mare 4 weeks ago. The horse is 6 yrs old, and being boarded. The first 2 weeks seem to be ok, other than the herd was showing her where her place is until she submits to them. Now for the last 2 weeks she is showing aggression in her stall and in the pasture to the head mare and other horses. Pins her ears back and kicks at them along with cribbing the fence panels if in her stall. Will also pin ears and start to crib if tied to pole and another horse comes near. I notice it more so when I come to see her or if there is feed in stall or pasture. I will admit that I usually have a treat for her. In the last week I have discontinued the treats, hoping the aggression will stop. The boarding manager is getting complaints about her kicking at the other horses, she kicked at a mare and almost kicked the owner that was walking one of the mares that is stalled next to her when on their way to their stall from pasture. She is kept in a stall at night next to the head mare and another mare. The head mare and her kick and bite at each other when in their stalls. They are let out to pasture during the day. We moved her to another stall yesterday hoping this will help. The boarding manager would like to move her out with another herd that is slightly more aggressive in hopes this will help her settle down. Before I bought her the previous owner had her with 3 other horses, she was not the herd mare. They seemed to get along ok. They would feed them 1 bale of alfalfa in morning to feed on all day. She currently is getting grass/alfalfa mix of 4 flakes by the boarding facility, 2 in the morning 2 at night. For the last 2 weeks I have been giving her 1 extra flake of grass and 1 extra flake of alfalfa at night because she was used to getting more feed than she is receiving. Plus she is not eating the grass, only the alfalfa. Need some help and advise.