I have an opportunity to get countryside organics feed for my flock, they deliver once a month. I already have 3 twenty week pullets on layena. I will be getting chicks first week of march, 15 of them. I already have a 50 lb bag of the purina Medicaid starter which I would prefer to use over non medicated (my friend is a vet tech and raises her hens this way). Anyway how long will that bag last them and then how many more 50 lb bags will I need for the pullets until age 18 weeks? I would like to feed the first bag of medicated then switch to the countryside grower. I don't want to have too much extra feed hanging around and would want to switch to layer once all the young pullets are 18 weeks. Thanks for the help.