There has been some discussion here about "is your FF really fermented?" But in a negative tone, implying if your FF doesn't ferment for long enough, it isn't "properly" fermented and you are "just feeding wet feed" and wasting your energy and fooling yourself.
I've asked the people who claim "my" FF isn't really fermented "how long" my feed needs to ferment before it is "proper," and how I could tell if it was "properly" fermented. I got nothing for useful answers.
I have, however, found one research study, which I provided a link to a few pages back, that was measuring the nutritional enhancements of a fermented grain product ... measurements were taken after one day of ferment, again after two days of ferment, and again after three days of ferment. This study indicated that the nutritional enhancements were evident at the one-day mark, but increased on day two and increased again on day three. The biggest jump, to my eyes, appeared to happen between days one and two.
But I have not yet seen a study that indicates at what "day" continued fermentation produced reduced returns. Or, indeed, if things can be fermented "too long."
Based on what I know and how we like to serve the FF here, I have arranged my fermentation system in buckets ... 5 total buckets ... I always backslop from the "oldest" bucket to the one I'm starting. My system allows for a maximum of 5 days ferment time. My goal is "at least" 3 days.
To backslop, I take a couple small scoops out of the oldest bucket, and then stir in the full quantity of water I'll use for my quantity of feed. I get that really well stirred up before I put in my feed. Then I stir my feed into the liquid, I stir it well. I've noticed that it seems to "start" fermenting a LOT faster with doing it this way instead of doing it the old way, which was to put the feed in the bucket, then put the scoops of backslop on top of the feed, then pour the water over that, and then stir. But that's just a procedural detail that isn't "necessary." The feed + water will eventually ferment regardless of what order I add things to the bucket.