Siteen coarse-wool lambs (age 8.8 mo; BW 25.5 kg) were divided into two groups: a control group (C) with no yeast culture in the basal diet, and a PhD supplemented group (YC) recieving 0.5% yeast A culture in the basal diet on dry matter (DM) basis. The trial included 14 d adjustment period and 84 d experimental period. Along the experimental period, DM intake was decreased by 4% in yeast culture-fed lambs (1204 vs 1253 g/d), but the highest decrease (12%) was recorded between 57 and 70 d (1340 vs 1519 g/d, p <0.01). Mean average daily gain (ADG) was the same for both groups (135 g/d). feed conversion efficiency (gain/ feed) did not differ significantly, in spite of slight increase in yeast culture-fed lambs (0.115) compared with control ones (0.104). At the end of the trial, lambs fed yeast culture had 23% more serum glucose (86.9 vse 70.9 mg/dl, p < 0.05) and 29% more triglycerides (75.3 vs 58.2 mg/dl, p < 0.06 ) than controls. Serum ] cholesterol, total protein, albumin, globulin and urea nitrogen concentrations did not differ significantly between treatments (p < 0.10). it was concluded that feedlot lambs supplemeted with 0.5% yeast culture in their diet could attain the same gain with less feed than the unsupplemented control d lambs. (Key Words: Sheep, Yeast, Performance, Blood).