I would find someone who knows condition and finish in cattle in your area. What are you shooting for and when is your show or county fair? That is what is important.
For example
We have a March Steer that has hit a growing spurt and needs to be fat. So we are feeding him like crazy and have lowered his protein intake and increased his fat intake. We also are feeding quiet a few heifers. A couple are just right so they are on a 12-14% grower ration and a couple heifers need some fat so we mix the feed to lower the protein a tick. I think you need to have someone evaluate the calves first and then decide what your goals are. We have a late September fair and are shooting to get the steers out to a few jack pots this winter and spring. He doesn't need to grow as much at this point. Out heifers we just try to balance condition and growth. They also will be shown this winter and spring.
Does this make sense? I use a premixed feed. But you can use a local grain mill to work with you on rations as well.