No such thing as a free lunch but there are some beneficial hacks to try. I dont always ferment but i do soak grain. It expands and so the birds gorge themselves less. Free range s much as possible will benefit more than anything but then you deal with predationand typical damage that chickens do. eg. Getting into gardens and scratching...
Discussion
I plan on building a run on a hill for compost production. Carbon, weeds, food, ect... get piled at the top. Chickens add nitrogen and move it downhill. I think I will let them out for a couple hours because I want them mostly working the compost. Not sure if I will do a couple paddocks or just let them free range and fence the garden. Once the grasses and weeds grow big enough I'll get the scythe out for material.