I'm interpreting your post that your chickens do go outside in an enclosed area? One way to supplement their protein is to hook up an outdoor light that shines on the ground inside their enclosure at dusk. It will attract bugs for them. Another is to give them table scraps - bones with scraps of meat on them, anything with cheese in it, leftover scrambled eggs. I'd avoid "junk food" and anything containing avocado but other than that, go for it. A third way to increase their protein is to give them access to seeds and grains. If their chicken yard gets scratched down to bare dirt you can plant seeds in pots and put a pot of mature grasses in their run so they can eat the seed heads. This time of year my chickens are leaping up to reach the seed heads of wild grasses but you could plant pots of barley or rye or other grains to give them. Or take a walk and collect wild grasses and give them a bouquet of seed heads. They will appreciate the variety!
I think we get sucked into believing that animals "have" to have a certain % of each nutrient and therefore we have to buy a commercial, pelleted diet. Really?? Like we balance our own meals that rigorously?? And would we enjoy them if we did? If there was a Purina Human Chow, is that what we'd want? Of course not. And neither do our chickens/dogs/cats/etc. Let them enjoy the foods they evolved to digest - and I'm pretty sure none of them evolved to digest pellets.
