Has anyone else had a horse this agressive towards other horses? How do you deal with it and correct it? I give her a firm no when she does it, but so far it's not helping
Yes, I have. When we brought the newest herd member home, my other mare absolutely HATED her. Would chase, charge, bite, kick, not let her anywhere near her or the other horse. Generally when the middle horse (like my mare) picks on the lower herd members, a good leader will step in and give that abusive middle guy a good bruising, just to teach him that such behaviour is unacceptable. Well, since there were no strong leaders in that particular herd, I had to do it myself.
I had someone else hold the new girl and brought my mare over. Whenever the mare pinned her ears and started looking mean, I gave her one good, hard, loud crack on the shoulder with the end of the lead rope. She only tried it about three more times, and then there were no more problems. At all. She'd move the submissive guy around a lot at first, but no more aggression, and eventually she stopped that. They'll never be best friends, but I don't have to worry about anyone getting hurt when I'm not there to watch them.
What do you do when you correct her? Just say "no"? The horse doesn't know what that means-you're probably just irritating her more than you're getting a point across. Basically, what .Delete. suggested. Carry a crop and give her a real good crack when she starts being aggressive towards the others, and make it count. Little love taps aren't going to do anything besides p*ss her off.
Besides that, I had a minor aggression problem with riding-that same mare didn't like others to crowd her. I would ride beside other riders and she'd start getting tense, but then a few weeks later we were sandwiched between two teams pulling wagons and she didn't bat an eye, and I wondered why this was. I found out it was because I would always tense up when other riders approached, and the mare detected this to mean that something was wrong when other riders came near, and she wouldn't let them. As soon as I relaxed, she didn't react anymore. My point is, be sure that you are relaxed and calm around the other riders. It could be that you're horse is just reacting to your tension.