The Purina Sunfresh group of feeds: Start & Grow (18%); Flock Raiser (20%); Layena (16%) consist of only plant proteins. I too first used these feeds and my birds did well on them but when I started breeding, I looked for a feed with both animal & plant protein. Also, my breed (Buckeyes) needed more protein (at least 28%)-- not all breeds need this and some actually do better on very low protein when growing (i.e. Jersey Giants, Javas, perhaps Brahmas). There were quite a number of poultry breeders who noticed lower fertility rates and also reported poorer feather quality with the advent of Purina (Sunfresh) and a lot of the other feed companies with "plant-only" proteins in the feed. Purina and other companies did this following the "mad cow disease" epidemic some years ago. I believe if you aren't interested in breeding but just keeping a backyard hobby flock, these feeds are fine.
The ADM feeds available to me only come only in pellets and contain animal protein too. However, my birds don't like eating pellets (or maybe it's because they can't waste it the same), and I don't like feeding them pellet-dominated-only diet. Another poultry breeder warned me about feeding pellet only diet {that they had experienced crop blockage}.
The Purina Game Chow group of feeds all have both animal & plant protein and is what I use now. All the bags look the same so you have to look at the tag (Startena--30% protein, Conditioner-20% and Layena-20%).