This research was conducted to investigate the effect of utilization mixture of some agricultural by - products silage (poultry manure, wheat straw, tomato fruits) on the visceral organ mass of Awassi lambs. A total of 20 Awassi lambs an average body weight of 21.5Kg. were used in this experiment. Lambs were divided into four groups of five lambs each. Lambs in the first group were fed a commercial concentrate feed mixture . Lambs in the second, third and fourth groups were with fed the commercial concentrate feed beside silage with rate of 15, 30 and 45%, respectively. Silage was fed instead of the same amounts of the concentrate feed. Lambs were fed their rations individually for 60 days. Type of diet had growth performance and variable effects on visceral organs. Lambs fed diet containing 15% silage appeared to heavier (P<0.05) trachea and lowest (P<0.05) weight of kidney compared to lambs in other groups. Also, they had the lowest (PO.05) weights of the omasum wet tissue, omasum and abomasums wet and dry contents. However lambs fed 45% silage diet had the heaviest (p<0.05) weights of the above items.