Thermo-ammoniated maize residues supplemented with 1% urea (Diet 2) or 4.5% fish-meal (Diet 3) and untreated maize residues supplemented with 2% urea (Diet 1), were compared on an isonitrogenous base. The in vitro dry matter digestibility for Diets I, 2 and 3 were 56.9, 62.5 and 63.1% respectively. Live mass changes for lambs receiving Diets 1, 2 and 3 respectively were -26.3, 19.9 and 94.0 g/d (P ≤ 0.05) while feed conversions for Diets 2 and 3 respectively were 33.8 and 9.5 kg dry matter required per kg live-mass gain.