If you had 10 cows instead of 5, and weaned 5 of the calves at 4 months, and fed them to 7-8 months, and left the other 5 on their mommas for 7-8 months, those still nursing will grow just as well, if not better. And there would be zero difference in what they'd sell for at a barn here in GA. You'd just have a lot more in the calves that you weaned too early and fed. You'd come out better feeding the cows, if they needed it. Time your calving for early April when the bermuda takes off, and wean them end of Sept, 1st of Oct when bermuda starts going dormant. But, if you weaned at about 6 mos or at about 450-500 lbs, with no feed, I think you'd come out better. Check the reports from barns down there. See what the 400-499 steers sold for, and what the 650 lb steer sold for. Figure the cost of feeding a 4 month old weaned calf for 4 months to get him to 650 lbs. Which sale do you carry yours to?