Pigs Can Detect Multiple Amino Acid Deficiencies in a Choice Feeding Setting

Background: It is unknown whether pigs can detect deficiencies in multiple amino acids (AA) and consequently change their feed choice. Objectives: We 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. Methods: Pair-housed 5-wk-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^–; and 4) Four-choice between LP^– and three diets supplemented with Thr, Trp, Val at +40% (n = 12 pens/treatment) from d0 to d21 (phase 1). From d21 to d28, AA concentration of supplemented diets increased to +60% (phase 2). Average daily feed intake (ADFI) and gain (ADG) were recorded. Results: Dietary 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). Conclusions: Pigs 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.