Posted this over on another thread in response to a fella's hens eating an inordinate amount of feed, in his estimation.
In the past, we never had to worry about animal protein because feed makers just routinely included it. Over the past few years, the move has been toward purely vegetable protein in chicken feed. I'm simply not a fan.
The old wives tale about birds needing corn in the winter to "warm them up" is largely a myth. Corn is a carb and produces energy. Protein is likely far more important to inner body temperature than carbs. In fact, too high a protein feed in the summer isn't indicated. Protein in the cooler/colder months is indicated. If the feed does not have adequate animal protein or no animal protein at all, it is my experience that the birds consume much more feed, seeking both the protein and the heat generating capacity required during the colder months.
I've found that when raising out chicks that a Gamebird formula, with 24% protein, largely built on animal protein (3rd ingredient in the bag tag) results in far less total feed consumed. A high animal protein feed base also allows for room in the diet for more whole or cracked grains and alfalfa meal, thus off setting the expense of the Gamebird feed. If that all seems too fussy, then feeding a layer formula of 16% protein is fine, if that protein is largely made up of animal sources.
Just my $.02. Hope it helps.