I would rather they ate a natural diet than anything processed and as mine are free ranging they eat plenty insects and worms so if I wanted to add to their layers and corn staples I'd go with other bird food type protein, mealworms, extra kinds of seeds, grains and nuts, or dig over a patch of soil so they can DIY. Things like rice, peas, porridge are all made from that kind of source, not kitchen scraps but prepared specifically for them and that would be the furthest extent I'd go from raw natural sources.
I wouldn't feed cow or fish to a hen and not just because I'm vegetarian and don't have such things in my kitchen, as if I believed it was right then I'd be buying it in for them the way I would for a cat or dog, but cats and dogs are predators and carnivores, hens are foragers and I reckon the most appropriate is to stay with what their system is designed to digest.