Data input is restricted to protein concentration (g/kg) and dry matter digestibility (%) of the forage, with annual pasture and forage residue biomass, nitrogen content and date of harvest sourced from the database of APSIM output. The digestibility and calculated intake determines the digestible and metabolisable energy intake which is partitioned into energy for maintenance, growth and lactation. The animal growth rates predicted by the model are in reasonable agreement with observed values (Fig. 3).