High quality protein sources are important for both animals and humans and to limit theircompetition, animals can be fed with alternative protein sources that are not-intended forhuman consumption is needed. The acid hydrolysis of feathers (EHFM) produces a product with a very high protein digestibility but the amino acid (AA) profile is unbalanced for pigs. Although unbalanced dietary AA profile can negatively affect the overall metabolism of pigs, it can be corrected by supplementing the diet with synthetic AA. The objective of the experiment was to compare the postprandial plasma profiles of AA, glucose, free fatty acids, urea, lactate, and insulin of pigs with contrasting protein deposition (adult vs growing pigs) potential after feeding diets either unbalanced (UNB) or balanced (BAL) in AA using EHFMas a protein source. The UNB diet for both sets of pigs had low levels of certain essential AA like Lys, Met, Tyr, and His while having high levels of branched-chain AA except for Ile. Therefore, their BAL diet was supplemented with these AA to attain a more favourable AA profile for pigs. All diets were formulated to provide the same amount of total AA. Four adult and four growing pigs were fitted with a jugular catheter for serial blood collection. After an overnight fast,pigs were fed 75% of their meal allowance, then blood was collected during 6h after the meal. Each pig received each diet three times. In both stages, feeding either diet didnot affect (P > 0.05) the average concentrations of total plasma AA. Supplementation with essential AA inBAL resulted in greater (P > 0.05) average plasma concentrations of Lys, Met, Ile and His, and of Tyr in growing pigs. However, supplementation of non-essential AA to both diets resulted in lower (P < 0.05) plasma concentrations of Ala, Glu, and Gly (and Ser, which was not supplemented) in BAL compared to UNB. Lower Ser and Gly may be due to the use of these AA for Cys synthesis. The concentrations of Thr, Trp, and Val did not differ between diets (P > 0.05). With the exception of Arg, Asp, and Tyr, growing and adult pigs responded in a similar way to balancing of the diet. Average postprandial plasma concentrations of the other metabolites and insulin were unaffected (P > 0.10) by the diet. In conclusion, AA supplementation to balance a diet results in changes in plasma AA profile in growing and adult pigs. Changes in non-essential AA may be due to their roles in carbon and nitrogen metabolism.