The coolest thing about chickens...is they eat everything. I think there are a few things you should keep away from them, like snails and slugs because they tend to choke on the slime, citrus because they don't like it, avoid feeding onions and garlic to egg layers because the taste transfers to the eggs, and cedar shavings because ingesting large amounts could kill a chicken. But mostly they eat anything.
Your basic chicken diet consists of proteins, carbs, greens and some calcium...in the natural world it's Insects, Seeds/Grains and Leafy stuff like grass....On a free range farm its Insects, Soy or Milk supply the protein and calcium (and Meats from dinner scraps), Seed from the land, and harvested grains such as Corn or Oats, and they free range on fresh grass, fruits, berries and leaves as they peck around the farm. Which is also important, because the chicken will peck and eat small amounts of pebbles and sand that are collected in the Gizzard, to help grind the seed before digestion.
Pre-Fab chicken feed comes in 3 styles, Mash (fine powdery stuff), Crumble (like Grape Nuts), and Pellets (a bit larger). Size of feed is relevant to how you want your chickens to behave. I read the pellets are wasted less and generally given to the adult chickens, and that the mash is used to keep chickens busier. They all have a balance of the Protien-Carb-Greens-Calcium-Grit all built in, but can still have trace amounts of bi products and contaminants. A 50lb bag of Pre-fab feed runs under $20...even here in Juneau, Alaska. The rule about how much chickens eat is: 12 birds will eat 50lb bag of feed in one month. For the beginner, such as me, I really just chose this Pre-fab feed to really make sure my first batch chickens aren't malnourished, and gave me more time to erect the coop and fences. I have this idea that eventually I will be smart enough to cut costs on feed by making my own. I am finding out now that what you feed a chicken, depends on what you plan on doing with that chicken...and how 'organic' you desire your flock to be.
A quick general feeding pattern for an egg laying chicken is different than a chicken you raise for meat. Also you can keep a laying hen as long as it produces the eggs (generally 2 years, but some say it depends on diet, and the chicken itself), and the meat birds are ready in about 8-10 weeks. Here is this handy chart I found online, but what it doesn't explain is the carbs. So in general; Protien = Energy for meat or eggs, Carbs = the building blocks for meat and eggs, Greens = Vitamins and complex amino acids. So the 'Developer' given to laying hens is basically higher in carbs than the 'Layer', which is higher in Calcium, for better Egg shell production. And the meat bird "finisher' is also higher in Carbs as to build more meat on the bird before slaughter. You can skip the Finisher and Developer stages, and all you will do is wait a bit longer for the bird to get there.
Lots of folks simply just add their own cracked corn or rolled oats to the layer feed and its home made 'Developer/Finisher'. Pound for pound, cracked corn and rolled oats are much cheaper than the Pre-fab food. Here is a cool fact, Cracked corn will raise the body temperature of your birds more than the oats will. I will probably feed oats in the summer and corn in the winter as a treat they would forage in the scratch area. Also, I hear, coming into your chicken's realm with treats such as this really help to tame your birds, and get them used to you and other humans to be around them.
I would like to finish this off by reminding people that I am not an expert on chicken nutrition, nor should you use this as a guide. There are plenty of resources out there to help you fully understand the feeding cycles you should have for your chickens. This is simply a gathering of the information that is freshly being researched by me right now. And as revelations hit me, I will be posting them here. There are many schools of thought, and some chicken farmers go to extremes to provide truly 'organic' meat and eggs like making their own feed mix for a particular climate or season, or replacing water with milk to produce thicker egg shells etc.
I know what some of you are thinking....if chickens eat anything, and basic elements of food are cheaper, why don't you mix your own feed for the chickens and go fully organic? This is a very complex adventure, as it requires learning the
Dairyman's Square rule, and also having enough chickens to keep this bulk feed on hand before it goes stale, which all feed does. I assume that would be a topic for another post, many months from now.