Feed, good feed is the cheapest thing you can do for these birds. It takes a lot of energy to produce eggs. Laying hens should get all they can eat. If conversion is a concern for you get a bunch of those little bitty Leghorns that lay like machines and dont eat a lot due to their size. I dont understand why anyone would consider rationing the amount of feed you would give to a laying chicken.
It is not unlike a good milk cow. A good dairyman looks for the cow that has the capacity to eat a lot of feed. It is the best indicator she will produce a lot of milk.
FEED EM