The objective of this experiment was to evaluate the addition of an α amylase to the diet on the performance (average daily gain (ADG), dry matter intake (DMI) and feed conversion (FC), apparent dry matter digestibility (DMD), intake pattern and net income of lambs fed with a high grain diets. The experiment was conducted using 20 male lambs (BW 24.36 ± 2.3 kg), allocated in a completely randomized design: Control (C) = 70% commercial concentrate and 30% alfalfa hay, Enzyme (ENZ) = C + α amylase. Lambs were housed in individual cages where performance and intake pattern were determined for 56 days; DMD was determined at the end of the experiment. Furthermore, the number of days and animals with reduced feed intake was estimated and economic analysis of the entire experiment was made. The addition of enzyme to the diet tended to reduce the DMI (C, 1.21 kg/d and ENZ 1.13 kg/d; P < 0.07) during the finishing period, the ADG and the FC were similar between treatments (P = 0.32, P= 0.095). The number of animals with a reduced feed intake more than 35% was higher in ENZ than in the control group (Fisher: p = 1, R 2 = 1). Feed costs with ENZ were higher than those of C group (P < 0.05). The increase in feed costs reduced net economic benefit with the α amylase.