SE8830 : Puzzling Machinery
They look like a specialised harvesting device to select and pick horticultural crops such as cabbage/cauliflower/lettuce.
Essentially a trailer with a delivery elevator on (this) end to load onto a second trailer alongside.
Several people can man it under cover and select individual plants as they are ready, roughly trim then they will run along a belt up the elevator.
Sounds a likely job for cheap(er) labour from Poland etc!
Incidentally -
SE8830 : Straw Bales is clearly straw not hay.