Purina Flock raiser has been fine here for decades! I always check the mill date on each bag, and only buy fresh. Feed stores will sell old stuff if they can, so watch every bag of whatever you buy every time. I much prefer there open dating too, and resent companies who use 'code' so the actual mill date isn't obvious. I don't remember who they are, sorry.
Purina Mills livestock feed is Not closely connected to the pet food branch, by the way.
Many companies got nailed years ago over the melamine from China disaster, and that problem seems to be over.
If you check the FDA or CDC or veterinary organization websites, or google 'pet food recalls' or 'pet food problems' there are ongoing issues with multiply companies over food safety.
Livestock feed is better regulated than pet food, as far as I can see...
Mary