Specific dietary selection for lysine, tryptophan and threonine by the piglet

Dietary selection for lysine, tryptophan and threonine was studied in three separate experiments using 48 crossbred piglets each. In each trial two reference groups and two amino acid choice groups were built. The reference groups were fed a diet containing either 0.70 or 1.25 % lysine in experiment I, 0.11 or 0.20 % tryptophan in experiment II and 0.57 or 0.67 % threonine in experiment III. The two other groups had the possibility to choose from pairs of diets containing 0.70 / 1.15 % or 0.70 / 1.25 % lysine in experiment I, 0.11 / 0.16 % or 0.11 / 0.20 % trp in experiment II and 0.57 / 0.62 % or 0.57 / 0.67 % threonine in experiment III. When offered pairs of diets with concentrations of 0.70 / 1.15 % or 0.70 / 1.25 % lysine, 0.11 / 0.16 % or 0.11 / 0.20 % tryptophan and 0.57 / 0.62 % or 0.57 / 0.67 % threonine, the preference for the diet higher in the concentration of lysine, tryptophan or threonine was 61 or 71 %, 87 or 93 % and 57 or 47 %, respectively. Results of growth performance and the preference for the different amino acids suggest, that dietary selection for amino acids in piglets is highly related to the piglet’s amino acid requirement.