The objective of the research project is to develop a mechanistic, dynamic growth model to estimate the partitioning of nutrients in the body and with which the slaughter performance of fattening pigs can be predicted. By integrating the existing knowledge on the physiological processes within the fattening pigs the model is to estimate anatomical body composition from nutrient intake on biological bases. It focuses on the rate of protein and lipid deposition in anatomical body parts during fattening period (25-110 kg) and on some qualitative parameters of the meat like fat content and fat to protein ratio in the muscle fraction at slaughter time. another aim is to demeonstrate the variations in body composition among sexes and genotypes at an identical nutrient intake. Different sexes and genetical backgrounds are varied regarding to partitioning of protein and fat deposition. An in vivo trial will be carried out to study the preference of different energy source on fat distribution in fattening pigs. Data from this experiment will be integrated to the models to verify the assumption and improve the weak points ot it. By the model the amount and chemical composition of different body parts like lean meat, backfat, organs etc. will be predicted upon various nutrient intake. This new model will also simulate the effects of difference in energy sources upon energy utilisation in the body and the fat to protein ratio in the meat. Consequently the model can be applied to develop feeding strategies to optimise pig production in different sexes and genotypes.