anything bruised has a limited shelf life.
if u mix it yourself apparently u need a license (!!!). but u can layer or put in separate conatiners.
barley apparently tends to fatten animals which for pigs isnt too good.
our harbro pig nuts are barley based, another brand we had (allen & page i think)was wheat based and they claimed to be for slower growing traditional breeds. find a book on horse nutrition, they will give u all the knowledge on grain values.
i remember when coarse mixes first came out (20 yrs ago) our boss made us separate every single pea, bean oat, barley, maize etc and weigh them etc so she could recreate her own mixes...took ages...lol