You could build a no waste feeder. I made a 5 gallon but you can use a lot of different containers, Totes, barrels, It depends on how much feed you it to hold. They work great!
I will second this. I LOVE(d) my no waste feeder. I didn't have a rat problem though. Trundle feeders and peck-o-matic style feeders are also great. Hope this helps!