Since you live so far from another source, I'd say to just quietly take your business elsewhere. You don't want to burn your bridges too badly. What if someone in the family becomes ill or injured, or you have vehicle problems and can't make the long trip? You might end up needing to slip over there and buy some small amount on rare occasions.
It's not the store's business if you decided to keep 100 bags of extra feed, or 1000. Their right to know what is done with the product ends when you load it into your vehicle.