What's everyone's protocol for prepping a horse for a long haul. I've done probiotic paste prior to and on arrival. But I wondering if there are other things I should be doing? I've heard of feeding vitamin C but I can't find a horse supplement for it. Any other steps you take for stress, gut, and hydration?

How long is he going to be hauling? Others on the trailer? Layovers? 

Is going to be 3-5 days depending on weather. Yes, layovers. She's coming up with a professional hauler. 

Google Vit. C for horses and alot will come up. Forgo is a good supplement to have them on.. 

Ulcerguard before and every day of the trip 

Would you do ulcerguard and a probiotic?

Personally I would not start a horse on a pro or pre biotic if they hadn't been on one previously. I think in this situation it may cause more harm. They are going to be stressed a little as it is for the long haul and you really don't want to be messing with it until they got home to you and settled. Now, forerunner equine does make a forerunner paste that I would use in a heartbeat. Its specifically designed for stress. One tube will last 1 horse 4 days. FORCO is another great pre biotic if you can have the seller or shipper start that a week before you leave etc. 

Personally I would give a click or two of bute and maybe a dose of Animal Eement In The Zone or something comparaible that will easy the gut but also serve as anelectrolitye to encourange drinking. I would do this each morning of the trip. 

Soaked beet pulp . 2 tablespoons salt daily. Rhino vaccine/ other. Coggins , health papers, brand inspection.