Thirty Barki lambs aged 5 months (22.90 ± 0.15 kg) were divided to three experimental groups (10 per group). First group (R1) fed CFM plus maize silage (60:40%), as control. Second group (R2) fed 60% CFM + 20%maize silage + 20% onion veins and lemon pulp silage (50% to replace of all MS). Third group (R3) fed 60% CFM + 40% onion veins and lemon pulp silage (100% to replace all of MS). The experimental period was extended to 5 months. Lambs were fed the rations with two levels from silage of onion veins and lemon pulp mixture and the roughage concentrate ratio was 60:40%, respectively. Results showed that values of pH were in normal range but there were increase in NH₃-N content, while there was decrease in Acetic acid content. R1 was related to be the superiority over the other ration for their GP, CH4_, DOM, and MCP and in- situ degradability. All nutrients digestibility and all rumen parameters were decrease by increased level of OLS replacement. There was decreasing in Malondialdehyde while there was increasing in CAT, SOD and GSH for R2 and R3 compared to R1. ADG was decrease while FCR was increase by increasing level of replacement. It is possible to substitution onion and lemon pulp silage instead of MS silage by 50% to reduce feeding cost and to obtain a relatively reasonable return but reducing the replacement rates to less 50% may be more profitable and without adverse effect on animal production.