This study used the multi-nutrient roughage blocks (MRB), including different replacement levels of sugar cane bagasse with orange pulp (OP), 0% for MRB1, 25% for MRB2, and 50% for MRB3. Three experimental rations were formulated using concentrate feed mixture (CFM) and MRB at 60:40%, respectively, as follows: ration1 (R1): CFM+ MRB1; ration2 (R2): CFM+ MRB2; ration3 (R3): CFM+ MRB3. Fifteen Barki lambs, with an average of 31.26 ± 1.70 kg of body weight, were assigned to three groups (5 lambs per group). Lambs were fed the experimental rations according to the nutrient requirements of the NRC (1985) for 84 days in a growth trial, followed by a digestibility trial. Rumen and blood parameters were also investigated. The results showed a significant increase in the final body weight (FBW), body weight gain (WG), average daily gain (ADG), and digestible organic matter fermented in the rumen (DOMFR) for lambs fed R3. The feed conversion ratio (FCR) and microbial nitrogen yield were significantly (p≤0.05) improved for R2 and R3 compared to R1. OP substitution did not affect the digestibility of all nutrients except for crude protein (CP) and crude fiber (CF). The concentration of total volatile fatty acids (VFA) increased linearly (p≤0.01), with the substitution levels being 12.81, 13.45, and 13.88 meq/100 ml for R1, R2, and R3, respectively. However, a linear decrease was observed for the population of total fungi in the rumen as the substitution level increased. No adverse effects on liver and kidney function were observed.