The use of ammoniated maize residue as a replacement for maize meal in the diet for fattening lambs, was investigated. Ammoniation of maize residue increased average daily DMI and ADG at the 0 and 20% concentrate levels. The feed conversions to carcass in lambs fed untreated maize residue with 40,60 or 80% concentrate were 14,0; 10,1 and 8,1, respectively, and for the ammoniated residue with 0, 20, 40, 60 or 80% concentrate were 14,6; 11,6;9,9; 9,4; and 8.5, respectively. Concentrate levels significantly affected digestibility in both untreated and ammoniated diets. Ruminal ammonia-N levels were between 180 – 250 mg/L and were significantly higher on ammoniated maize residue at the 40 and 80% concentrate levels. Ammoniation of maize residue increased lamb performance at low concentrate levels.