FWIW, I think I see two little bubbles there, so I think it did start fermenting.
There's no sign of mould so I too would let your chickens decide if they want to eat it or not, and if you try it again, try with just grains; you'll find it quite a different experience - and a lot less smelly! :D
the feed part is probably making it smell 'funky'; the corn and oats would produce the yeasty smell. Stirring isn't necessary. Have you seen any bubbles? Can you post a photo of it?