The calves are recorded in D23 or D24 depending on their final use.
If the calves are to be slaughtered before 12 months to produce veal meat, they are recorded under the heading D 23 - Calves for fattening. When they are sold, it has to be recorded in table N, heading 23.
If the calves are not to be slaughtered to produce veal meat, they are to be registered under the heading D 24 - Other cattle less than 12 months. These calves will become breeding animals or adult fattened animals (heifers, bulls, steers). It does not matter if the calves are sold or kept on the farm.