Hi, hope you are enjoying BYC!Just tried fermenting my chicken's feed. I have a quick question since I've seen differing comments on how long you can let the feed ferment. Should I finish all of the feed by four days or is it ok to use the fermented feed and keep adding new grains to the starter feed indefinitely? Thanks for your time!

Most of us ALWAYS back slop (leave a healthy portion behind) a bit of the FF into our new batches. It gives you a good starter to ferment your next batches much faster(for some only overnight after adding new grains/feed). In other words, just keep it going.

In fact I NEVER clean my container other than rinsing down the sides. The sides of the container can grow mold (not desirable), but the FF itself should not.
The amount of time it is OK to feed out your FF will vary with your weather. When it's hot it ferments much faster. I try to keep mine at about the 4 day level of ferment because it seems like a sweet spot to me.
Good luck, and don't forget that SOME chickens will require more than 1 introduction before they start really enjoying it because they are creatures of habit and this is something new to them.
