BackgroundIt is unknown whether pigs can detect deficiencies in multiple amino acids (AA) and consequently change their feed choice. ObjectivesWe investigated whether pigs compensate for a diet deficient in three AA (Thr, Trp, and Val) by selecting multiple diets and whether this compensation is affected by the supplemented AA concentration. MethodsPair-housed 5-week old pigs (n= 96) were exposed to one of four treatments: (1) AA-adequate: offered a low protein (LP) diet adequate in AA for growth (LP+); (2) AA-deficient: offered LP diet deficient in Thr, Trp and Val by 20% (LP-); (3) Two-choice between LP+ and LP- (4) Four-choice between LP- and three diets supplemented with Thr, Trp, Val at +40% (n=12 pens/treatment) from d0-d21 (phase 1). From d21-d28, AA concentration of supplemented diets increased to +60% (phase 2). Average daily feed intake (ADFI) and gain (ADG) were recorded. ResultsDietary treatment did not affect ADFI and ADG in phase 1 (P>0.05). In phase 2, ADFI and ADG were higher in AA-adequate and Two-choice treatments than in AA deficient treatment with Four-choice in between (P<0.05). In both phases, Thr, Trp and Val intake was lower in AA-deficient treatment than in other treatments. For the Two-choice treatment consumption of LP- was higher than LP+ in both phases (P<0.05 and P<0.001). Four-choice treatment consumed more LP- and Trp-supplemented than Thr- and Val-supplemented diets in phase 1 (P<0.001); in phase 2 consumption of the Trp-supplemented diet was the highest (P<0.01). ConclusionsPigs can detect multiple AA deficiencies and compensate by consuming AA-supplemented diets. In a two-choice setting, pigs proportionally decrease consumption of a supplemented diet with increased dietary AA concentration. However, when given the choice between individual AA supplemented diets, pigs proportionally decrease consumption of a highly concentrated Val diet and increase preference for a highly concentrated Trp diet.