If taking filler into account, Lily Enstomach's appearance in the anime proves they can. Whilst filler, it is noted that Oda has some creative influence over filler arcs, meaning they probably wouldn't do this if it contradicted his own ideas by too much.
yes I think all the animals of One Piece can eat a DF and get more than vitamins. Humans, Merfolk, Giants, Longarms, reindeer, cows and the other rare species mentioned at Sabaody.