Abstract: Two experiments were carried out to evaluate the effects of cellulases supplementation on in vitro degradation of date kernels (the first trial) and in vivo (rumen fermentation and nutrients digestibility) by lactating Zaraibi goats (the second trial). In the in vitro experiment, dry matter and organic matter disappearance (IVDMD and IVOMD) were determined for date kernels supplemented separately with (Asperozym) and commercial cellulolytic enzyme source (Veta-Zyme Plus®) at 3 levels (15, 30 and 45 U kg–1 DM) compared with the control. The highest values (p<0.05) of IVDMD and IVOMD were observed with Asperozym supplementation level at 45 U kg–1 DM compared to control. While, Veta - Zyme Plus® gave the highest (p<0.05) IVDMD and IVOMD values at 15 U kg–1 DM compared to control. In the in vivo experiment, nine lactating Zaraibi goats after 7 days of parturition were divided into three groups, three animals each, using 3×3 Latin square designs. The first group was fed 37.5% Concentrate Feed Mixture (CFM), 12.5% date kernel and 50% berseem hay (control diet). The second group was fed control diet supplemented with Veta-Zyme Plus® at level 15 U kg–1 DM (T1). The third group was fed control diet supplemented with Asperozyme at level 45 U kg–1 DM (T2). The results indicated that Asperozym and Veta-Zyme Plus® supplementation significantly (p<0.05) increased nutrients digestibility, nutritive values, ruminal Total Volatile Fatty Acids (TVFA’s) and ruminal ammonia nitrogen (NH3-N) for treated groups compared with the control group.