USE-2 or even URD is likely cheaper, and doesn't require conduit, being designed for direct burial - but at that point, you might as well hard wire a panel to the barn. Play nice with the Building Inspector and the permit people, set aside a few extra dollars for the tax man.If you are worried I would just run an extension cord and buying a chicken safe heater. They do have mr buddy heaters that run off propane some are safe for indoors. But you then run into problems might have to build a box around it so it doesn't get knocked over. If these a permanent areas and you own your property and aren't renting. I personally would just bury some electrical cord with pvc conduit and make a glorified extension cord. Basically that's what I did with mine.
(I'm doing this soon, actually). Need to measure my "spare" RHW-2 wire, hope I have enough.