Believe that each state kinda has their own laws on hauling horses.

I use to haul a lot of horses but they changed the rule since then.  I know government horses must be able to stand naturally in the trailer so on ave that would some where between 7-71/2 from floor to ceiling.   I have heard that is suppose to be for all horses now but not sure if its true.   As far as them be hard on a trailer that depends if they have been hauled before and how good a ride you give.

Horses kick the hell out of your trailer.....not worth tearing your trailer up

I cant remember the exact year...believe 2005 but the government passed a law banning hauling horses in a double deck pot. I know because I used to haul them from Oh to Tx. Its now a federal offense to do so.

First off, your post question leads to the lack of studing laws in the first place. Slaughter horses are not moved to kill plants in the USA anymore since too many winey ass people thought it best that we should all find a place to go with horses that need to be put down. Oh yah, and we should all help their cause by giving them feed and donating to their cost because they took on more than they could chew... Trust me I had a large name in the horse industry trucking and importing..

Now on to trucking horses in a pot. Almost all states (excluding to the best of my knowledge New Jersey) you can load personal, rodeo ect. in a pot. no deck height requirements by the fed gov as they have no clue between what an iceladice or a irish drought is. If you decide to go into the business of moving them to Canada to the plant prepare to pay out the but in international health certs at beter than $115 a pop. With the most recent of $0.25 per pound paid... not much profit margin. Go south to mexico and skip the international health cert cost but take your chances going back and for to mexico. The only almost up and running plant soon to put down horses to get our intenational trade back with Italy and Russia would be in Warm Springs OR. It is on the reservation, so the question always came up as would the government actually let the indian nation do something us soil can't do? and if so would it then be blocked from actual shipment off the reservation.

Good luck. You may have a better chance moving fats to the kill plant at $2.68 a mile!