The experiment was conducted to assess the ileal digestibility values for the purpose of evaluating the ability of 14-day-old broilers to utilize the amino acids (AA) from different plant feeds. The feeds included two cereals: maize and wheat; full-fat seeds of rape (FRS); four local by-product: cold-pressed rapeseed cake (RC1), rapeseed cake from precooked (90°C) seeds (RC2), solvent-extracted rapeseed meal (RSM), maize distillers dried grains with solubles (DDGS), and soyabean meal (SBM), used as the model protein feed. The standardized ileal digestibilities of AA (SID) were measured using the assay diets containing Cr₂O₃ as an indigestible marker. A protein-free diet was formulated to estimate the basal ileal endogenous AA losses. Dietary protein in the assay diets was supplied solely by the test ingredients. Each diet was offered for 5 days to 4 replicate cages of 12 birds. For wheat the SID coefficients of most AA were significantly or numerically greater compared with maize. The numerical superiority of the SBM over all the other protein sources tested was found for SID of most AA, with statistically confirmed differences for threonine, tryptophan, serine and tyrosine. Among protein feeds examined DDGS had the lowest digestibility of lysine, methionine, threonine, tryptophan and cystine. Of the four rapeseed feeds, RSM had the lowest digestibility of lysine, histidine, alanine, glycine and serine. Considering the SID of the 18 amino acids, protein-rich feeds tested in this study were ranked as follows: SBM > RC1 > RC2 > FRS > RSM > DDGS. However, the SID values of lysine and methionine in both rapeseed cakes (RC1 and RC2) were comparable to those obtained for SBM.