Thirty weaned Barki lambs with average body weight 27.56±0.57 kg were blocked by weight and randomly distributed into three equal groups to investigate the impact of feeding trimming waste of mandarin trees (TWMT) on productive performance of lambs. The first group of animals was fed with Berseem hay (BH) plus concentrate feed mixture (CFM) without any additives and kept as a control ration (CR). The second group was fed TWMT plus CFM as untreated ration (UR), where, the animals in group three received TWMT plus CFM supplemented with Bio-Magic with level 10kg fresh matter/ton CFM and kept as a treated ration (TR). Feed was offered as 70% CFM of the total requirements for growing lambs and the roughage was offered ad lib. The results were summarized as follows:- CR group had higher digestibility than other groups. Sheep fed TR ration revealed lower TDN compared to the other groups. The DCP was significantly higher for UR and TR than CR-The CR group recorded the lowest value of N-retained however no significant differences were recorded between UR and TR groups. -The ADG for TR group increased by 4% and 15.9% compared to CR and UR, respectively.- Feed conversion was the best for lambs fed TR, while UR recorded the worst value.- The best economic efficiency recorded by TR. -It may be concluded that, TWMThas the potential solve to reduce shortage of roughage feeds for animals in Egypt; furthermore reducing feed cost under desert conditions.