Diagram of the beef cow-calf herd dynamics over a year. Each box represents the between-group transitions at a given time in the year. A diamond symbolizes a selection process. Groups are the following: calves from birth until weaning, male and female weaned calves for sale (grassers), heifers younger than 2 years kept for breeding, bred heifers, cows from the first pregnancy diagnosis until fattening decision, cows from fattening decision until culling, and bulls. Calving, breeding, grazing, and purchasing/selling periods are indicated and correspond to the reference scenario as described in section Initial conditions, reference scenario, and simulations.