You need to blow air through it to dry it out. I assume this is whole kernal corn, not on cobs, and not already ground?
http://www.dultmeier.com/products/0.1642.2519.2520/3279
This would be an example of a small hand screw in type of aerator that will move air through a pile of grain. At farm sales I see used ones go $50 from time to time.
Heat as well as air would work faster; but just air will work too.
Or, you can freeze it.
Or, make it wetter, compress it to eliminate all air, and make silage out of it. (This isn't an easy option for the amount & type of stuff you have....)
Those are about the only ways to make it keep.
Sounds like you are on borrowed time, if it is warm already, & you see signs of mold, it won't keep another week as it is. I don't have a good suggestion, I assume you are not in a position to find on of those aerators.
This was a difficult harvest in many areas, the corn was very wet & very late last fall, what is happening to you is common. I put 500 bu of corn in my wooden grainery to feed to the cattle over winter. Didn't quite get it all fed, mine is going bad too now with the warmer temps. Shoulda got it fed before spring in my case.
--->Paul
Edit: you said you had feed made, so perhaps it is ground or crushed feed now?
Going to be hard to blow air through that.
Can you add some oats into the mix, bring the moisture content down - oats is full of air around the hulls & often pretty ddry, will allow your feed to have a lower overall moisture content.
The sealed barrels are also trapping the moisture in the feed - as they heat, the moisutre rises, and has no where to go.
Here when I would feed ground feed in fall from new ear corn, I needed to feed it up in a week, couldn't grind more than that at a time. I understand your issue, I just don't think you will have a good solution from where you already are at?