We send 15+ to the butcher each year (direct sale beef). Our local lockers are taking 2025 bookings (booked out 18+months). We just booked dates for the calves that are in utero. Genetics plays a huge role in both growth and marbling (we raise PB angus and angus/wagyu crosses). My dad sent truck loads of fats at 20 and 22 months for decades. This past year our first group went at 15 months and they were 1,400-1550 in weight (to big and one of those was an angus/wagyu cross (50% wagyu)). Most of the rest went at 16-17 months and were in the 1300 range. We are confident our beef would consistently grade prime.
My dad never used creep so neither do I. Weaned calves start on corn immediately after weaning (have used rolled, ground, and whole (WSC)). 2-3 lbs initially and step up monthly until we get to 12-15 lbs by finish (I used to feed a much higher corn ration but corn at $7/bu forced an adjustment in ration which we've stuck with). From weaning to finish they receive alfalfa baleage, dry hay, and corn stalk bales in free choice feeders (along with corn ration).