Apparently, at my 50k home, my piggies have grown too rich of a taste. Since I introduced the Piggy Feeder, they refuse to east food off the ground when the Feeder is empty...unless I pick the food up and drop it, or just place food.
I think this is somewhat buggy, as I was initially shocked to see over 1000 grain untouched and a horde of starving pigs.