I don't agree. My chickens don't waste much and if there's some on the ground they clean it up good. If it attracts predators depends on how secure your setup is. I have had none such problems in the years that I have had chickens.
My birds do not waste any and I feed roughly 1/2 to 1/3 what they would consume if they did not have access to quality forage.
Most of my raccoon and opossum visits are first targeting feed out after dark, attacks on birds are usually secondary. With current free-ranging setup my feeding stations are more than a hundred feet away from where birds roost. Varmints no longer a problem for me because of dogs.
Best measure I have is that productivity does not decline until crops are empty too early into night or birds range too far.