Twenty one growing crossbred ram lambs with average body weight of 19.67±0.42 kg and 4 months of age were divided into 3 similar groups (7 in each). All animals were fed diets consisted of 50% concentrate feed mixture (CFM) plus 50% berseem hay (BH) in the 1st group (control, G1) or plus 50% conserved mixture {sugar beet pulp (SBP) + BH, 1:1} in the 2nd group (G2) or plus 50% conserved mixture (SBP+BH, 2:1) in the 3rd group (G3). Results showed that CP and CF contents decreased but NFE content increased in diets of G2 and G3 than in G1. Lambs in G2 showed the highest (P<0.05) digestibility coefficients of all nutrients and TDN value, while, G1 showed the highest (P<0.05) DCP value. Lambs in G3 recorded the highest (P<0.05) DM intake. The TDN intake was higher (P<0.05) by G2 and G3 than G1. Lambs in G1 revealed the highest (P<0.05) DCP intake. The highest (P<0.05) ruminal pH value and NH3-N concentration was recorded in G1, while, G2 showed the highest (P<0.05) ruminal TVFA's concentration. The highest (P<0.05) concentrations of total protein, albumin and T4, was found in blood plasma of G2, while G1 had the highest concentrations of globulin, T3, urea-N, AST and ALT. Glucose concentration was nearly similar in all groups. Lambs in G2 showed the heaviest (P<0.05) weight, the highest (P<0.05) total weight gain and average daily gain, followed by G3, while G1 had the lowest values (P<0.05) Amount of DM and DCP/ kg gain was higher (P<0.05) for G1than G2 and G3. Amount of TDN/kg gain was nearly similar in all groups. Economic feed efficiency was higher (P<0.05) for G2 and G3 than G1. Lambs in G2 revealed the earliest (P<0.05) age, the heaviest weight, the highest scrotal circumference and the highest testosterone concentration at age of puberty, followed by lambs in G3, while those in G1 had opposite trends. From these results it could be concluded that lambs fed diet containing conserved sugar beet pulp (50% sugar beet pulp + 50% berseem hay) showed the best results concerning feed intake, digestibility, nutritive value, rumen fermentation activity, growth rate, feed conversion, economic efficiency and earliest age at puberty