The requirements of a weaned piglet are expected to change systematically over the period 6kg-25kg. Commonly during this time animals will be offered two diets. However, initially on each diet the animal may be restricted because it's protein requirements are in excess of that supplied by the diet. Then latterly, amino acids may be oversupplied requiring deamination of the excess by the pig. This is a costly process, in terms of the energy required by the pig and commercially, in terms of food protein costs. This system also does not take into account differing individual requirements within a group of pigs due to genotype, sex, maturity and stage of growth. As a result potential benefits are to be obtained if weaned piglets can be shown to choose an adequate diet, meeting their individual requirements, when given a choice of feeds.