When I was doing fermented feed on a regular basis, I had to go through pains for it to not get too funky, and had to clean out the bucket a couple times in the summer. It should be better in the winter, but you just want to make sure they are getting the right microbes. Your nose will let you...
I would guess that you would need a strong lacto culture of some sort to make sure it lacto-ferments, since the wild yeasts will typically get there first. No one wants drunk chickens. 😅 Or will it just turn into vinegar since it is an aerobic system?
Maybe a sourdough culture would be best...