This is definitely bothersome, but I have had the same bag since the beginning and have found nothing. But, next time I need some, I will look for another brand. I don't think I have many options though. Its tsc or a local feed mill. The feed mill has manna pro. 😬
I use the manna pro and have ever since I got chickens 5 yrs ago. My ducks nibble on it as well. The bag lasts quite a long time. I've never had any issues, but as with all things, inspect before giving it to your chickens or ducks.