This paper reports the results of the work of the “Nutrient requirements of heavy pigs” ASPA Commission. The Commissionwork was mainly focused on the problem of identifying a good and flexible methodology for establishing nutrient requirements of heavy pigs in Italy, in a situation where the major part of the pigs are used for ham and other typical products. Nutrient allowance was considered to be a variable open to manipulation, since its optimal definition depends on the specific circumstances of each single production unit. It appeared that the most logical way to account for the many interactions involved was to integrate available information using computer simulation techniques. A methodology based on the following steps was proposed and analyzed: i) selection of a mathematical model to describe the chemical growth of pigsover time as result of the interactions of genotype, feed and climate; ii) developing suitable equations to predict the qualityparameters of the carcass and, if possible, of the single cuts from the body’s chemical status and implementation ofthese equations in the model; iii) identification of production targets and use of the model as a tool to simulate the effectof different genotypes, feed and climate on the productive and the economic results. A model strongly rooted in a theoreticalframework, simple enough to be applied in practice and requiring a limited number inputs was selected from literature.From a preliminary evaluation, performed by using experimental calorimetric data, it was concluded that the modelwas potentially able to accurately predict the chemical growth of pigs under different conditions of feeding and climate.The major lack of knowledge regarded the values of genotypic descriptors of the national pig populations, the evaluationfor which some simple experimental protocols are described in literature. Other lack of knowledge involved relationshipsto predict the anatomical growth and the evolution of quality parameters of carcass and cuts from the chemical compositionof the body. If a correlation between the chemical composition of the pig’s body and production targets is confirmed,then a link between the farmer and the industry can be established and the model could be used to identify more convenientfeeding strategies. The conceptual basis and the way to assess nutrient requirements of heavy pigs have beenclearly identified.