Fermented feed. There are other forums with a wealth of information about it. I'm doing it for my chickens. It's easy, better for the chickens, makes their poop smell better, and helps make the food last longer. On the downside it does have an interesting smell and takes a little more work than just dumping dry pellets into a large feeder.
And chickens really seem to like the taste of it better than the "straight from the bag" feed.