Unusual rear bumper - what is it?

[Ozark Tim]

I have had 2 of them. Both were on trucks that I bought from livestock farmers (hogs) in Southern Illinois.
I am fairly certain that besides the ability to unstrap and drop the tailgate down low, if you were a hog farmer you removed the tailgate the day you bought the truck, installed a rack with a sliding door for herding livestock into the bed and it allowed you to back up to a livestock ramp without a gap for the animals to turn and jump off the tailgate.
Make sense?