A 42 day trial was conducted to investigate the effects of prebiotic (Fructomix) and organic acids (Orgacid), either singly or in combination, on morphological and physiological performance of broiler chickens. The studied characteristics were growth performance, lymphoid organs weight, antibody response against sheep red blood cell (SRBC) and cell-mediated response to phytohaemagglutinin-P (PHA-P). Two hundred one day old male broiler chicks were randomly divided into 20 experimental units. Birds were offered either a corn-soybean meal basal diet (control) or the basal diet supplemented with 1 gkg-1 Fructomix (FM), gkg-1 Orgacid (OA) or a mixture of 1 gkg-1 FM plus 2 gkg-1 OA (FM+OA). The results showed that body weight gain and feed conversion ratio were significantly improved by FM and FM+OA diets compared to control diet from 0 to 42 days of age. On day 35, the toe web swelling (cell-mediated response to phytohaemagglutinin-P) in the birds fed with OA or FM+OA diets was significantly higher (p<0.05) than the control birds which were fed with corn-soybean meal basal diet. The spleen relative weight and secondary anti-SRBC titers in the birds fed with OA and FM+OA diets were also significantly higher than in birds fed the control diet, where the birds received FM+OA diet had the highest secondary antibody titers. However, feed intake, relative weights of thymus and bursa and primary antibody response against SRBC were not significantly affected by dietary treatments. In conclusion, the addition of FM or FM+OA in the diet of broiler chickens improve various growth performance, besides improving birds immunity system
