I am courious as to why people haul horses with their heads sticking out of the drop down doors? To me this seems so obviosly unsafe for so many reasons.
A scared horse might try to escape out the window.
Flying things lijke birds and bugs hitting a horse and possibly an eye at 65 mph or other road debris getting kicked up like part of a tire or garbage.
Getting too close to a vehicle in the next lane. I could see a semi veering accidently and chopping a head off.
Clipping a branch and hitting the horse.
Getting in an accident with a head hanging out doesn't sound pretty.
Same goes for letting a dog hang out the window or ride on the back of a truck. I came upon a dog limping on the side of the road that I thought the vehicle in front of me hit. Seems the dog had jumped out the back of the pick up and had gotten run over by his boat trailer he was pulling.