A feeding trial was conducted to evaluate the influence of live yeast culture (Saccharomyces cerevisiae) on milk production, composition, and some blood metabolites of Ossimi ewes during the milking period. The control group(G1) was fed a concentrate mixture (CFM) and hay (H) and grazed twice daily, while the second group (G2) and third group (G3) were fed the same diet supplemented with 3 or 6g of live yeast culture (Yea Sacc1026), respectively. The treated groups had significantly higher values (p<0.05) for fat corrected milk (FCM) (740, 605, 571 g/day, for G3, G2 and G1 vs, respectively), while the values for milk yield, fat yield and lactose yield were higher (p<0.05) only in G3 compared with G1. Milk yield values were constantly higher in G3 than in G1 while the values for the G3 were more variable during
 milking. Milk composition was not significantly affected by yeast supplementation
with the exception of urea values which were significantly (p< 0.05) lower in G3. Yeast administration influenced β-hydroxy-butyrate (BHB) values, which were significantly (p<0.05) higher in the treated groups; and non-esterified fatty acids (NEFA) values, which were significantly (p<0.05) higher only in the G3 compared with the G1. Other blood metabolites values were not influenced by the treatments. It was concluded that supplementation with live yeast culture, under the conditions of this experiment, had a significant effect on the performance and metabolism of Ossimi ewes during the milking period. Based on more constant results, it is recommend to include live yeast culture (Yea Sacc1026) at 6g/animal/day as appropriate level for field conditions