This thesis was made to create a new version of the Edinburgh Model Pig computer program, to build a factorial computer model of nutrient utilisation by the breeding sow, to validate the Model Pig and the Model Sow, to expand the modelling function to economic aspects and to link with other packages relating to the feeding and management of pigs, and thereby to build a bio-economic model package of pig production systems. Chapter 1 describes the background of the use of models in pig science and production and indicates the purpose of the present work. Chapter 2 introduces the concepts of compensatory growth theory, heat production and the Gompertz growth function. The use of the Gompertz function and ash contents of the food to predict daily protein retention and water retention was also introduced into the model to test whether these concepts can be used in the new version of the Edinburgh Model Pig. The result shows that the trend of response is consistent with published experiments. Chapter 3 uses those concepts described in the Chapter 2 to create a version 2 of the Edinburgh Model Pig. This model has been extended to include the important weaning period (5 to 20 kg) by improving the prediction of voluntary food intake through the effect of ambient temperature, bulk of the diet, and stocking density. The model provides a graphic function to plot comparative daily biological data. The model indicates the limiting factors in terms of diet (protein, lipid or ash), environment (cold or hot), the situation of food intake control (bulk, allowance or refusal) and compensation of protein growth.