Rotting is not quite the same as fermenting~a little past that stage....but either way, chickens have the digestive systems that handle and do very well on "rotted" foods....fermentation is the stage that is the most beneficial, nutritionally speaking. The "mother" in unpastuerized apple cider vinegar that everyone crows about being beneficial? A yeast/mold glob of "good" bacteria and enzymes that aid the digestion and increase the absorption of nutrients consumed.
The vinegar that you use on salads? Rotted apple juice, essentially, that has been allowed to convert to alcohol and then to vinegar as a finished product.
Yogurt? Rotted, moldy milk. As is cottage cheese and any other kind of cheese. They call it "cultured"...but it is cultured with yeast/mold spores that increase the nutritive value and preserve the food in a different state.
Wine? Rotted grape juice.
My chickens regularly eat all the "rotting" fruit and veggies out of my garden and orchard with no ill effects because they are NOT humans and their digestive systems are designed for consuming these items. Same with dogs....they can drink stagnate water and eat rotten meats that we could not.
Gotta stop thinking human and think chicken, folks. We wouldn't thrive on eating our own feces either, but the birds do and gain added protein to their diets.