Instructions
Establish a dominant position with the mare. She needs to know that you are to be respected. This first step must be in order before you can address any attitude problems the mare may have while she is in heat.
Do not beat or manhandle the mare. To earn her respect simply means that she needs to see you as the alpha horse. Take as much time as necessary to make this happen. With most mares a few verbal reprimands and some decisive body language will settle the issue. With some, it may take some serious sessions in the round pen before she will acknowledge your dominance.
Handle the mare extensively on her next estrus cycle. Demand that she keep her attention on you, especially when she is around other horses. Do not allow her attention to wander, as this is when most bad behavior will manifest itself when she is in heat.
Ride your mare as well as handle her from the ground. Do not allow her to kick at other horses or act aggressively. If she shows signs of acting up, reprimand her and bring her attention back to you. Again, this does not mean be overly forceful. Use just enough force to get your point across, and then immediately release the pressure.
Praise her when she responds to you. Do not be so edgy that you cannot relax and enjoy your mare--even when she is in heat.
How to Handle a Mare in Estrus
Whether it is a stallion, mare, or gelding, each horse has its own challenges and characteristics. A mare in estrus can behave entirely differently than she does when she is not in her breeding heat. A docile, easy to handle mare can become cranky, irritable and aggressive. Have sympathy for your mare to give you more patience, but do not allow her to act poorly merely because she is having a hormone issue.