When using a premix, use what the premix says to use, usually boneless meats from the store. The only thing I would worry about adding to a premix that it might not sat is omega 3s, everything else should be in there, and the omega 3s might be, but they are very sensitive to degradation.
Fresh from the store should be parasite free, I still freeze pork, just in case. Also, if you know any hunters and get meat from them, that needs to be frozen first.
As long as the expired stuff has not defrosted and been refrozen, I would feed it. Just be aware that some of the vitamins may have degraded and don’t feed solely it for a long period.
