He has obviously had trauma with dogs before, and it's not likely to be trained out of him--at least I don't think it could be. Perhaps, since you don't have much attachment to him, find him a new situation and remove the chance of your dogs getting seriously hurt or killed.
I don't necessarily think a dog-aggressive horse has "obviously" had trauma with dogs before...my gelding was never even around dogs until I got him as a 3 year old, and he is the same way. He has settled down, but the first year I had him, he literally spotted the dog in the field and took off after the unsuspecting dog, and literally ran over the top of the dog leaving hoof prints on the dogs ribcage as she tumbled out from behind him.
"If you think nobody cares about you, try missing a couple payments..."
Horses are prey animals and dogs are predators. I don't think a horse has to have had some kind of dog trauma to want to stomp dogs. I think the exception is more a horse that likes dogs, and that on the spectrum you have mostly horses that will tolerate dogs. Keep the dog out of the horse's yard.
JMO of course.
He is total garbage! Quick! Hide him on my trailer (Petstorejunkie).
Some horses just don't like dogs. A friend had a horse that would seek out dogs and try to stomp on them, just as you described. This horse had never had any trauma with dogs. We tried to train it out of him but he was never trustworthy around dogs.
I think the no climb fencing is a good idea if you want to keep the horse.
I can understand. I have a multi-critter farm. Horses are for my pleasure (lol, sanity, stress relief, love of my life) but everything else is for profit.
Indirectly, this includes my dogs. I can't farm without dogs, they have jobs to do and I need them to do it.
If a horse is stomping smaller animals - this is a problem!!
When I first got my mare, she wanted to strike at my goats. I acted like I was another mare and the goats were my foals. I squealed and charged at her and chased her around 10 acres like it was a round pen until she was licking her lips and wanting to stop (I was exhausted, lol)
We did this a couple of times, any time she so much as pinned her ears at a goat or dog I got after her. Now she LOVES the goats, when her favorite goat was kidding, she made a pest of herself wanting into the kidding pen with her. If she feels like she has to go all the way across the pasture, she will gently herd the goats up, as if they are HER foals now.
This may not work for every horse. She was only just 4 when I got her, and she got to feeling maternal about them, which a gelding might not. But she went from me really thinking I may have to sell her to loving the goats and being very tolerant of all else.
Also, don't underestimate horses. She, and every other horse I have known. quickly learn which dogs are theirs and belong to their home and which dogs don't. My mare won't let strange dogs in the pasture, but now flat out ignores all 6 of ours.
I'm fortunate that my dog aggressive horses are only aggressive towards strange dogs, not my own. All of my horses are trained to NEVER EVER kick or strike at any dog while under my control, but I can't see how one could train a horse loose in his pasture to do the same. I'd probably replace the horse- I also think more of my dogs than I do any horse.
*Very few dog-aggressive horses got that way from previous bad experiences with a dog.
Some just are very territorial against any perceived intruders. Doesn't have to be a predator, some can be this way with goats and I've even seen it with rabbits.
At best you can work with/train them to NOT attack when you're visible. But no, you'll never train/desensitize a dog-attacking horse to the point where the dogs are safe.
At that point your choices are to completely seperate dogs and horses and make sure it stays that way 100%, rehome the dogs, rehome the horse. And there's absolutely nothing wrong with sending the horse to the next owner with full dog-attacking disclosure. (which many owners see as a bonus, depending on their situations)
I say rehome the horse to keep your dogs safe. Sounds like that's the best option for you. It would be much too difficult to retrain multiple/old dogs to stop living the way they've always lived, not to mention change your entire lifestyle, for the horse.
I'm on my fourth personal Dog Hating Horse. It hasn't been a big issue for me ever because my very first horse loathed any and all dogs. So for me to keep dogs and horses seperate wasn't unusual. I've seen a few dogs killed and a handful or so more seriously injured by horses. Some by dog hating horses (one by mine)and a couple by accident. Accidents happen, you can't change that. But you can protect your dogs by removing a known danger to them.
Keep your property safe and peaceful and find the new guy a new home. Sad that it didn't work out, but horses are rehomed all the time and this just isn't a fit for either of you. And it would be a lot sadder if/when the horses catches a dog.
You jump in the saddle,
Hold onto the bridle!
Jump in the line!
I personally don't think you can train the stomp out of the horse. I also believe that hard-core stompers have a reason for being that way. I'm not talking about the horse that will give chase, I'm talking about the horse that runs down a dog to hurt it.
I have one of those hard-core stompers and I don't have dogs off leash. The farm where my stomper was born had great danes that enjoyed running along the fence and barking at the foals. I suspect there might have been some foal chasing in the pasture and taunting in stalls as well. I can't blame him for not liking dogs...