Blankets, hay and fresh water. In the car -so much crap 😂
I always bring an extra lead lone and halter and of course, you always have to have both human and horse first aid kit!!
I like to keep it simple, panic hock tie and hay net. And it depends on the setup of your trailer if it has places for horse tack or not
Trailer ties are amazing for safely hauling horses. Saddle stands if not already built in trailer are a must have. Bridle hooks, a traveling tub (large tool tubs, husky or sterilite) to hold necessary items. Water if not provided at location. Everything possible!! :)