If you want maximum protection and minimum maintenance, a waterproofing wood stain is your best bet. It's better than paint. Paint sits on the surface of the wood and eventually chips and flakes off. Then you need to scrape it off to repaint properly, which is more work and more mess. The stain, on the other hand, penetrates into the wood and offers better protection. Also, to reapply, you don't need to scrape anything off - you just apply the new stain right on top of the old layer. It lasts longer, too - 25 years if used on fences and 10 years on decks. BEHR makes waterproofing stains that come in solid colors, too, not just semi-opaque "wood colored" colors like stains usually come in. Just make sure you paint it on thin and rub it into the wood so it gets absorbed instead of pooling on the surface. If it's too thick, it will chip like paint. I don't like leaving unprotected wood outdoors, even if it's pressure treated, just because I want to extend its lifespan. The elements can be harsh on wood. Especially something that chickens will be pooping on. I doubt that spool has had any treatment (like pressure treating) so I would recommend giving it something.
