This research was conducted to investigate the utilization of silage made from some agricultural by – products (poultry manure, wheat straw, tomato) for the growth and finishing of Awassi lambs. Silage was made by mixing of poultry manure, wheat straw, and damaged tomato fruit at rates of 50, 25 and 25% respectively. Sugar was added to the mixture at 3 percent to increase the rate of fermentation. Six months later, silage was analyzed for its chemical and physical characteristics. These examinations proved the quality of the silage and it was ready for use in fattening rations. Twenty Awassi lambs were used in the experiment. Lambs were divided into four equal groups. The first group were fed a commercial concentrate (80%) plus (20%) vetch hay. The second, third and fourth groups were fed the commercial concentrate and silage at rate of 15, 30 and 45%, for these groups, respectively. Silage was used to replace hay and partial amount of concentrate. Lambs were fed their rations for 60 days on group basis and their daily feed intake was recorded. Lambs were weighed individually on weekly basis. At the time of termination the trial, three lambs from each group were slaughtered and eviscerated, weight of carcass, visceral organ gastrointestinal tract component, and content were recorded. The performance of lambs fed the 30% silage diet showed more yield than that of other groups. Average daily gain in lambs was 0.34, 0.33, 0.37 and 0.31 kg for lambs fed the control diet to 45% silage, respectively. Similar trends were observed in feed conversion ratios which were 4.8, 4.5, 4.5 and 5.3 kg feed/kg gain for lambs fed the control diet to 45% silage, respectively. The cost of gain was significantly (P < 0.05) the highest in lambs fed the commercial diet and the lowest in lambs fed diet containing 45% silage. Lambs fed diet containing 30% silage had heavier gastrointestinal tract components and contents. They had heavier (P < 0.05) weights of head and legs and longest small intestine, compared to lambs in other groups. Lambs fed diet containing 15% silage had the lowest weights of the measured items. However, lambs fed the commercial diet had the heaviest (P < 0.05) weights of the items measured.