Chasing other animals

Question
Hello,

I have a large dog (Boxer x Bull Arab) who was thought to be the breed previously mentioned. After a while though I am starting to think she is part Herding Dog too, here's why:

Chases other dogs in dog parks when they run fast
Nips an animal to get them to play
Chases and nips horses to get them to run
Barks and nips if they don't move
Focuses on only the 'prey' and nothing can stop her.

I have tried so much but am really struggling. Today was the last straw as she was kicked by a horse in the upper arm and will probably need vet treatment tomorrow.

With the horses, she is fine when I am on top of one. Even if I'm galloping she just follows without any problems. However when making a horse run on the ground, or in a paddock etc. she will chase them, get under their feet and nip them. I've tried the 'out' meaning out of the arena but she comes back in when she gets excited. I've tried tying her up but she yelps, barks and if a horse comes past her she will jump out and try and bite it. What are your suggestions for this?

I've stopped taking her to the dog park so much as she didn't listen to me and got bitten almost every time (I'd like to take her sometimes for socialization). When someone throws a ball for their dog she will sprint after the dog, not the ball. She gets right in their face and usually the dog snaps. Putting her on a leash makes her jump, bark and whine. She won't listen to me at all when she gets into that locked mode. She usually finds a certain dog and annoys it. Even after the ball has been thrown, she follows it everywhere and sometimes will nip its scruff to get it to chase her or run. When she does this she will not listen to me and I have to chase her to get her. Is this her prey drive in maximum effect? What are ways I can try to fix this?

Thankyou so much!

Answer
Amelia, prey drive and the predatory sequence (eye/stalk/chase/grab/kill/dissect/consume) is instinctive in all dogs.  The degree to which it exhibits itself can vary among breeds and within individuals in the breed.

First, you must not allow your dog to be put in a position to practice this behavior.  If this means confining her when you are working the horses, then do it.  Your dog park experiences sound like they are not fun for anyone. Don't continue to allow her to bully other dogs in this way.  This isn't good socialization for her - she's practicing bad behavior.

Then, teach her to come when called reliably. You start with a low distraction environment and gradually build up until she's reliable in a variety of different circumstances.  Your rewards must be on a level with the distraction you're calling her away from.  Use chasing YOU as a reward; whip out a tug toy when she gets to you; toss a ball as a reward.  Be exciting.

There's a great online course that I highly recommend.  Check out Susan Garrett's Recallers class.  It's offered at only certain times, so be sure to get on her mailing list to find out when it will begin again.  Watch the success story videos on YouTube.

Until you have that reliable recall, don't allow your dog to rehearse these predatory behaviors.