I feed purina flock raiser. I wouldn't say it is molding, it is dark. There is something growing on the metal trash can I store it in, not on the feed itself, but on the sides of the container and it falls into the fee. You can see the stuff growing and falling in. It has a sweet, perfume smell and is nearly the same color as the feed. It doesn't seem to be bother the chickens. I assume there was moisture in the feed so I poured it out on some paper to dry and the stuff started growing on top and around the feed. There was a ring of the stuff around the feed in a matter of a couple hours. What the heck?