So do you call it by how many horse spaces there are like with vans, or how many animals you actually have loaded? You could haul five, but they only loaded four animals. Guess a 4-Up (literally!) does sound better than a 5-Maybe.
That is one incredible load, thanks for sharing. Does give "creativity" for when you "just have to get there", a new look!
I think Horses in Haiti posted pictures of the local transport once, they are called Tam tams, or something like that.
And Bluey has a photo of back in the day getting a working horse from one end of the ranch to the other.
The truck bed frames are available commercially, or were, my buddy had one for the back of his '70's model Ford to haul sheep.
ETA I opened the photobucket link and got a good look at the pic I hope they aren't going far!