This experiment was conducted to determine apparent and true amino acid digestibilities of untreated (BPS), heat-treated (HBPS) and thermal-ammoniated (NH3BPS) high-tannin sorghum with pigs both intact and with an ileo-rectal anastomosis (IRA). The mean endogenous protein secretion for the surgically modified (12,1 g CP /d) and normal pigs (5,8 g CP / d) differed significantly (P ≤0,01). A net synthesis of isoleucine, lysine and methionine was observed in the large intestines of normal pigs fed the sorghum diets. In general, the mean apparent and true faecal and ileal digestibilities of amino acids (AA) were the highest for NH3BPS, followed by HBPS and BPS. Thermal ammoniation improved the true ileal digestibility (as measured with IRA pigs) of arginine (28,3%), methionine (22,9%), valine (42,8%), histidine (22,9%), isoleucine (8,8%), lysine (27,3%), phenylalanine (27,3%), threonine (24,6%), serine (17,0%) and tyrosine (6,9%). Although ammoniation improved AA digestibility, the improvements were too small to be of practical importance.