Here in Costa Rica there are 3 types of chicken feed available in the stores: starter, layer and meat raiser. They all basically have the same ingredients, only the protein percentage varies, and the layer has more calcium. They range from 14% protein (layer) to 22.5% (starter).
There is no organic feed nor is there feed certified GMO free. People 'get around' the non organic issue by free ranging and feeding corn or cassava - but the corn you can buy in the stores is GMO.
Which is a problem if you don't want to eat GMO.
So I'm in the process of making my own feed. My flock doesn't free range (yet), making me 100% responsible for their food. And it's quite a lot of work.
I can buy organic local corn at the farmers market - sometimes. Corn has been called chicken crack and they do love it. It's low in protein (9%), high in carbs (82%), I think 3% fat. Sounds great, but I can't always get it. It turns out that jackfruit seeds are almost the same nutritionally, so I use those when we have them. The seeds have to be boiled, dried, ground and fermented to deal with the anti nutritive aspects, but that's okay as I ferment the food anyway and the boiling is the only extra step in the preservation process. I'm looking for more carb sources. The cassava sounds interesting, and we could grow it: it's just such an empty calorie that I'm resistant.
Protein I get from black soldier fly larvae, azolla and duckweed, sprouted lentils and gandul /pigeon peas. I'm working on growing guppies in the azolla / duckweed tank for an extra protein source.
Fats from black soldier fly larvae plus little bits here and there. BSFL are 35% fat.
Minerals and vitamins come from greens: spinach - Brazilian and Okinawa, katuk, tradescantia, gandul, nacedero.
Calcium from egg shells, snail shells, seashells and BSF. I can't find oyster shell here: as the layer feed has 'sufficient' calcium, the feed stores don't sell it.
They also get whey and / or curds 2-3 times a week.
Dry feed is fermented. Very easily done - put dry feed in a buck