Aloha,
I bought 25 pounds of flax from the feed store. I think it costed $22. I figure it adds Omega 3s to my eggs, so I spend extra. Triple duty is what they call it at the feed store, I might be a little wrong on the name. I will be switching to laying pellets instead of the triple on my next bag as my birds are getting close to laying age. I have 1 layer and 7 juveniles. Use whatever feed you like.
The Korean Natural Farming method calls for feeding raw brown rice and bamboo leaves to day old chicks, so I say give it at any age. Brown rice is the cheapest of the three that I use. Unhusked brown rice is the major backyard chicken feed in Asia. It's the cheapest. Just not too much nutrition.
I also feed lettuce and leftover food. I grow the lettuce, and I give the junk leaves to them. They love it.
I am also looking into growing Black Soldier Fly Larvae. You can look it up on Youtube. I will probably use a 55 gallon plastic drum and make a ramp for them to crawl out of and into my cup. Now that is inexpensive feed, especially if you have access to wasted food like a grocery store, restaurant or cafeteria.
I said one cup to start off with, how much depends on how many birds you have, just save some to keep the fermentation going at all times. Also, I didn't make clear maybe that it needs to be covered with water all day and night, to keep it anaerobic.
All in all, I'd say Use equal amount of brown rice and feed in the morning and equal amount of flax and feed for the second part. so 50% feed, 25% flax, 25% rice.
Fermenting helps break the food down and make more nutrients available for digestion.
I'm kinda new too, but I've been researching a lot.
take care, Puhi