Teaching new puppy to be a good barn dog

I just brought home our third Boxer, an 8 week old male, and want to teach him to be a good barn dog. I moved my two horses home almost two years ago and prior to that, my other two dogs had never been around horses but they both have a healthy respect for them and really don’t go near them. My younger male has thought about chasing them when they start bucking and playing in the pasture, but my pasture fencing is electric and after getting zapped he won’t go near it anymore. However, I’ve never had to teach a puppy how to behave around horses and I want to keep him safe, first and foremost.

I set up a puppy playpen in my aisle so that he can watch me when I’m in the barn and he can see and smell the horses while staying out of harms way. So far, he’s taken zero interest in them. Eventually, I’d like for him to be able to roam the property without having to worry about him bothering the horses or getting kicked or stepped on. So, what’s next?

At 8 weeks I don’t think there’s a whole lot you can do, other then not letting him eat poop!
But in all seriousness let him get used to the horses but don’t let him do things like go in the stalls or paddocks if that’s the end goal.
Free lunge or have the puppy near by when the horses get running around. If he makes any inclination that he wants to chase them, say NO, and redirect his attention to something else and then reward.
Other then that I would just make sure he knows all the basic commands like sit, stay, and out.

When I got my current dog she was already 1.5yo. She knew basic commands, but it took awhile for “out” to click. It finally did one day when she came into the indoor ( she was allowed to stay in the sectioned off corner with the couch), I yelled Out! and trotted straight at her. She figured it out quick, and it reinforced her mind that horses are not afraid of her and that she always needs to be the one to get out of the way.
I’m in no way recommending this for a puppy.

I just got a 4 month old puppy in June. I started out on a leash outside the pasture introducing them. Then went to a long line. Eventually let him tag along with me. Fortunately for me, he is farm more interested in what they are eating. He does like to help me warm up though. He runs down the rail when I’m walking and then runs back and barks. Horse ignores him and he leaves when we start trotting.