Background: This study aims to determine the effects of supplementary diets with date waste and Saccharomyces cerevisiae on biochemical parameters in Ouled Djellel ewes at early and late lactation. Methods: Thirty pregnant ewes, were divided into 5 groups. All ewes received wheat straw (1Kg),in addition to wheat straw, the control group (33CON) received 500 g of concentrate. The other groups (8.33REB,25REB, 16REB,16REBsc) were fed with a mixture of date waste and concentrate in different proportions,and Saccharomyces cerevisiae at a rate of 2 gr/ewe for the 5th group. Blood samples were collected at the beginning and at the end of lactation to determine biochemical profile by spectrophotometry.Feed analyses were performed according to AOAC standards. Results: Ewes fed the 8.33REB,25REB,16.6REB,16.6REBsc rations had lower serum levels for the majority of biochemical parameters compared to the 33CON control group.The results indicated that serum glucose, aspartate aminotransferase and urea decreased slightly in the groups supplemented with date waste and Saccharomyces cervicea (P and lt;0.05)whereas,albumin and cholesterol were marginally significant.Therefore,date waste could be distributed, partially to ewes as an alternative to concentrate.