Fermenting like we are doing with chicken feed is known as "wild fermentation". It's a battle of various yeasts, molds and bacteria, some beneficial and some not. If the "good" guys win, you have healthy fermented feed, one that is acidic. Sometimes it goes bad. Some possible reasons it can go bad:
- Poor water...contaminated or chlorinated
- More "bad" microorganisms than the "good" guys can beat
- Inferior fermenting media, aka cheap chicken feed
For the cheap chicken feed, I don't mean to imply that inexpensive feed is always going to produce poor results. But when the feed is not "as nature intended" aka full of pesticides and other chemicals from industrial farming practices or has been poorly stored or processed before it became feed, then you have better chance of having a wild fermentation going wrong. If you got mold on your feed while fermenting it, it could very well be that the feed was moldy to begin with. It may have been dry, but had gotten moldy at one point in the process from farm to silo to bagged feed and was full of dry mold spores, just waiting for some moisture to come alive again. I believe I have heard that corn is particularly prone to mold.
One thing I do, at a minor added expense/effort, is to add a bit of blackstrap molasses to the water before mixing it with the feed. The molasses provides an instant easy source of food for the yeasts. The yeasts in turn then become food for the lactic acid bacteria. Plus the resulting yeasts/bacteria are even stronger because they are getting highly digestible minerals from the molasses. It's not essential to fermenting feed, but I like doing it knowing it is invariably providing extra minerals to the chickens, besides making for a moderately better ferment, IMO.
If you get white fuzzy stuff (very thin fuzz, not thick fuzz 1/4"-1/2"), then most likely it is yeast. Like someone else said, the yeast doesn't cause an alcohol problem, because other microorganisms will keep it in check. I don't brew any alcohol, but I'm sure alcohol producers go to great lengths to promote alcohol production over lactic acid production. I have had some of my lactic acid human brews go alcoholic on me and I never did figure out why.
If you do get mold, you have two options: 1) stir it in and wait a few days to allow the beneficial microbes to consume/neutralize the mold, or 2) scrape the mold off the top and any feed that doesn't look or smell right. I've done this with sauerkraut many times, in which the top moldy layer was nasty and underneath that was delicious, healthy kraut. In fact, before we as a society became such germo-phobes, this is how people use to make all sorts of fermented foods...they got a moldy top layer and it was just scraped away and discarded.
The opposite of wild fermentation is a lab project. Commercial yogurt is made this way. The (pasteurized) milk is inoculated with a pure strain of bacteria known to produce yogurt. Then the yogurt is sometimes pasteurized again to kill all bacteria and yeasts. The sour flavor and thick texture is still there. Then in order to be able to list the yogurt as having "live cultures", more pure strain (lab derived) lactic acid bacteria is stirred back in. People used to make their own yogurt (and many still do), using raw milk and backslopping with a bit of previously made yogurt as the starter culture. This is known as a wild fermentation or heirloom. The heirloom yogurt starters (just a bit of yogurt from a wild fermentation) have a very wide range of different yeasts and bacteria, which tends to allow for more robust results under a wider range of conditions and milk quality that can make very good yogurt. Look up "Heirloom Bulgarian yogurt" for an example.
Probably more info that you wanted, but I am passionate about fermented foods!
My last bit is that some folks feed their chickens exclusively fermented feed. I don't. *I* don't eat a diet of 100% fermented feed and why should my chickens? And they would never eat such a diet in the wild, but would likely come across all sorts of rotting, fermenting, molding foods along the way. My chickens love to sift through our various compost piles, which are full of mold, among other things and they are as healthy as can be.
