It’s a fairly common practice when feeding alone to put the pickup in gear, preferably low-low range 4×4, climb on the back and begin flaking the alfalfa off in pieces small enough so that all the cattle get equal chances at the hay. The first prerequisite is flat ground, occasionally looking up to see where you’re heading, conscious of rocks, holes and trees. The ‘on and off’ the back of truck gets trickier with age, flatbeds much safer than pickup boxes, in my estimation.
Just out of college, I was feeding out of the back of a standard pickup in ‘autopilot’ on rough ground. Hit a bump and fell over the wheel well, but fortunately my boot toes were stuck under the remaining hay bales with my heels wedged against the inside fenders, leaving me upside down, head hanging inches from the ground and no way to get loose. Arms flailing and bouncing towards rougher terrain and the creek, I managed one great sit up to get upright, get off and get the pickup stopped.
A man takes pride in the damnedest things: I like to have my flakes well-spaced and even in size with no gaps in the design that they and the cattle make on the ground. Though I aim the truck initially, no two designs come out the same. Then quickly disappear.