The main possibility would be to keep and expose cows to rebreeding for spring/fall calving. The 2nd solution can be to put bodyweight on and market as cull cows later. Bob Birdell, who farms and it has a cow-calf herd around Stanberry, Missouri, reported he attempts to look at age, https://lostcalfhatco46790.yomoblog.com/34326443/lost-calf-shirts-fundamentals-explained