I only do it as a winter substitute for foraging. Nothing really "replaces" foraging in my way of thinking. (How can you replace the rich finds of roots, bugs, seeds, and stuff that they dig up while foraging?) Growing a few greens in the kitchen sunshine is just a way to get some chlorophyll, etc., etc., in my chickies. If you research "wheat grass" on the internet as a people food, you'll see how great it is for chickens. But mine is just grown in water. The chickens would only be getting what was in the water and what was in the grain ... sort of like a bread and water diet. Ugh. No fun for them is my guess.
However, since our layer feed is pretty decent and contains a lot of things that they wouldn't get if they just ate wheat grass--namely things like animal protein in the fishmeal, minerals (calcium, phosphorus, manganese, magnesium, salt, traces from Redmond conditioner, etc.), good fats from sunflower seeds (mostly), iodine, etc., in the kelp, the probiotics, and the list goes on a little bit--I would think I was really depriving my chickens and risking their health if I grew fodder and only fed them that all winter.
But I don't know everything there is about chickens and tend to be a worry wart. If someone is feeding a straight diet of fodder all winter to happy egg-laying chickens, then great! That would definitely be a cheap way to go. I'm just too chicken to try it, and my wheat grass growing system of a few plastic spinach containers from Costco couldn't keep up.
You were wondering about how much to feed them. I just give about 20-25 chickens about one container a day. That's about a rectangle 5" across and 14" long. And I don't put a very deep layer of wheat in there either. It's about ... hmmm. I guess it just barely covers the bottom of the container, but it does cover the bottom of the container completely. Then it grows up to be about 4 inches long. Sometimes the hens don't eat it all and then I have weird frozen root clumps
