when changing the feed depends on what protein level you want for more meat on the chickens body weight
and always change feed by adding 1/2 new feed and 1/2 old feed till old feed is used up so they don't get like not eating new feed
actually I always left mine on grower til 8 months old
that gives them more protein level in the feed
especially if you are feeding grains as treats
the grains apprx are
corn 9-10% protein
wheat 11-13% protein
oats 11-13% protein
so say you are feeding 18% protein in crumbles
this is how you figure protein amts
say using
a large ceeal bowl of each of the above
that would total 54% protein divided by 4 bowls full and it would be 13-1/2 % protein they would be eating
so you have to remember when feeding treats it deminishing the amount of body protein it is giving the birds
always give granite grit if feeding grains