I've been feeding whole grains to my birds for years. They get a 50/50 mix with a 24% protein crumble, that I have made at a local mill, inwhich, I also have them add essential vitamins and trace minerals and pulverized krill for Omega-3 amino acids. It ain't cheap but my birds are extremely healthy and produce strong chicks that hit the ground running.I've been looking into feed recently and found a lot of information about feeding whole grains for better health. Feeding whole grains increases the size of the gizzard, making it more efficient and hostile to salmonella. Chickens are also very good at eating what they need.
http://www.lrrd.org/lrrd17/4/pous17045.htm
http://www.sterlingcenterfarm.com/Feeding/Wholegraindiet.htm
https://www.gardenbetty.com/garden-bettys-homemade-whole-grain-chicken-feed/
https://academic.oup.com/ps/article/87/3/405/1494457