[QUOTE=SonnysMom;8212766]
I have been hauling horses in a straight load for 25+ years. Most of the time I leave the top doors over the ramp open. I tie my horses and my horses are big enough to hit their heads on the roof long before they could flip out.
When I trailered a weanling for a friend, top doors were closed. I trailered another horse that due to a long story we changed the trailer to a box stall and the pony was loose. The top doors were closed.
I do think with any set up a horse or pony can find a way to hurt themselves if they try hard enough.
My horse went over the breast bar and got stuck. Had a pony rear up as the owner was loading and he hooked a leg over the center divider when he came down. There is a video of a horse that went out the front window of a slant load and got stuck half way out.
I have horses that generally haul well. I would prefer the extra ventilation of the back doors being open. Like another poster said I had a Cotner that had a back tarp instead of doors. Back in the day 60’s, 70’s and 80’s many trailers didn’t have top doors, just the roll down tarp.[/QUOTE]
A horse can and will be able to flip over the back partition with the back windows open, regardless if their head hits the top of the trailer… imagine what would happen to the horse if this happened on the highway - he would honestly likely be dead from impact alone, flipping out the back of a trailer going 60-70 MPH… not worth it, for me. I won’t trailer with the back open, and I don’t even think it gives that much more ventilation given that it’s the back that is open and not the sides or the front.