feed rations?

I'm sure this isn't a new subject but what I'm feeding may be. I get my feed in bulk from a local COOP. I am feeding my calves currently after weaning until late Septembers. Most will sell and keep 4-6heifers for replacements. I currently feed a generic COOP mix with Ruminsen, corn, soybean meal, molasses, etc. in it. The question being should I change my mix once I am only feeding cows and heifers? Granted my heifers are separate from cows until spring. I hear alot of people using cotton seed hulls. We did for show calves, not sure why. My dad was a genius Ag teacher and I just fed. Wish I had paid more attention. My neighbor feeds soybean meal, chopped corn, and molasses to cut dust and sweeten it.