A complete diet (Total Mixed ration) with sorghum stover (40%) as sole roughage source was prepared and offered to animals under two forms: as mash or as expanded-extruded pellets (EEP). These two complete diets were compared with a conventional diet (ad libitum chopped sorghum stover fed separately with concentrate mixture to meet 80% of protein requirements). These three diets were randomly allotted to 30 male lambs for a period of 150 days. The lambs on conventional, mash and pelleted diet grew with an average daily gain of 62.5g, 78.5g and 101.3g, respectively, with superiority (P<0.01) of EEP diet in relation to the others. The lambs fed complete diets were more efficient in utilizing the dry matter (DM) than those fed conventional diet despite lower DMI. The haematological (total erythrocyte and leucocyte counts, and percentage of neutrophil and lymphocyte) and serum biochemical constituents (total protein, albumin, globulin and urea nitrogen concentration) at 0, 75 and 150 d of trial were not affected by diets, except haemoglobin concentration which was significantly higher in lambs fed EEP diet (P<0.001). The lipid peroxidase activity was lower (P<0.05) and the RBC catalase activity (P<0.01) was higher in both groups of lambs fed with complete diet. The humoral immune response against Brucella abortus was higher in lambs fed with EEP diet compared to the lambs fed with mash or conventional diets. The total Ig, IgM or IgG titres against 20% chicken red blood cells were higher in lambs fed complete diets and were not affected by expander extruder processing. The cell mediated immune response of lambs assessed as in vitro lymphocyte assay at 150 d of feeding was higher (P<0.05) in EEP diet followed by those in mash complete diet and lastly by those fed conventional diet. پرونده مقاله