I tired it. Only benefit was reduced waste. I can get the same reduced waste benefit by buying pellets. Or by serving feed as a wet mash (which i do) without the effort of preparing half a 5 gallon bucket of fermented feed three days in advance (longer for people in less conducive climates), and without any concerns of an undesired "something" colonizing it instead.
I don't have to dip a ladle, strainer, or my hands into a wet or cold bucket, I don't need to set space aside for it, I don't have to worry about periodically cleaning my system.
Pour, wet, stir, dump.
And if I'm pressed for time? Simply dump.
My time is worth FAR more than the benefit I obtained fermenting - which even when I had a flock near 100 birds wasn't noticeable. If it happens when I've pre-measured feed for my wife to dsump while I am travelling, I don't object - but I don't make any effort at it, ewither.
If you are fermenting in mason jars because you have a handful of birds and it gives you pleasure? Go ahead, its your entertainment. But the bird's nutrition isn't markedly better , and you aren't saving any money. (fermentation is complicated, details matter - kimchi is fermented. So is wine, beer, sourdough bread, yogurt and pickles. Fermented feed is no different. What ingredients are you fermenting? under what conditions? with what microorganisms? with what liquid? Plain water? what is its pH???)