Dont forget first aid gear for you and horses. And picket pins if you have to unload the horses and tie them off somewhere while working on things. Tow strap so someone can tow you out of trouble, or if you have to pull someone else out. Get a lock for the hitch connector on the trailer. If you have to leave the trailer alongside the road, there's a better chance it will still be there if nobody can hitch it up and drive away with it.
Marl developed quite a list of trailer survival gear over the years, and that was just going back and forth to dressage shows. Of course, most items were put on the list after we found out the hard way that they were needed.
Good timing on the steak....we've got more rain showing up on the left side of the radar.