I first read about fermenting chicken feed here
https://www.backyardchickens.com/t/644300/fermenting-feed-for-meat-birds
This blog has a page with a good summary for beginners if you don't want to wade through the long thread, tho it does have a lot of good info.
http://naturalchickenkeeping.blogspot.com/p/fermented-feed.html
In a nutshell you moisten the feed with water and add either unpasturized apple cider vinegar with it's mother or some whey from yogurt. The bacteria sort of predigest the food and in the process make some nutrients more available. The bacteria are also good for the gut and help with the digestive process, which also increases the amount of nutrients available to the bird. Folks are reporting reduced feed usage on average about one fourth to one third the usual amount. ***You leave some feed in the bucket to innoculate the next batch, so normally you do not have to keep adding the whey or vinegar each time. After awhile your bucket of fermenting feed will smell like vinegar and the longer you keep it going the better it seems to get.
Fermented feed reduces pasty butt and cocci in chicks. It eliminates the diarrhea and stench of CornishX meat chicks. People are reporting an increase in the size of the egg yolk and many will be keeping records this spring to see if bigger yolks lead to bigger chicks.
Being moist it is harder for the birds to scratch the feed out of the feeder so less is wasted. Being moist also means that the finer bits swell up and stick together so they get eaten too.
You can ferment any kind of feed or grain.
Some chickens can be reluctent to eat it in the beginning, but if that is the only thing offered they will eat it at least in a day or two and after that they are pigs at the trough. I have birds swarming me when I open the gate, jumping into the bucket before I get all the way into the pen, even tho there is a little bit of feed left in the trough from the day before. My chicks get it from the first day.
Thank you so much!! I am excited to do this..