I broke and trained some horses until I was in my 40’s. The most powerful, and last, I broke and trained was a gray mule. I had him green broke, but he hated dogs. I hit the ground one time too many when a dog got close. I wanted to ride him in our local wagon trains instead of my horse but since so many bring dogs on the train, that wasn’t going to happen. We took him to the Columbia Mule Days and sold him green broke with a warning about dogs. LOL
My dad raised Belgian horses. I tried to talk him into breeding one of his mares with an American Mammoth jack to get a really big mule, but he wouldn’t.