at any reputable grain goes through a dual cleaning process before being processed into feed. as far as the fertilizers they use for it most grain crops and hay are ghrown with a 16-6-12 blend. its a great blend for grains. the potash for it comes from a pit (out of the earth) in new mexico...
the only additives in the layer feed i get is lysine which last tiome i checked is just a mineral. the company i use is bryant grainand its just strictly texas grown grain straight from the panhandle