I noticed when I set eggs this time I had a few with bacterial rings. Now some of these were my own and some were shipped eggs I bought. The last bag of shavings I bought were cedar. I buy busted bags at half price at work so it's kinda you get what you get, so to say. Has anyone used cedar and noticed more bacterial rings during incubation? It might have been something else, I just wondered. My coops are open on the front so ventilation for the birds is fine and I have never had any problems. I also sterilize the incubator.