The current study was conducted to examine the effects of an herbal compound, a probiotic and an antibiotic growth promoter (AGP) on the performance, intestinal bacterial population, antibody titers, and morphology of the jejunum and ileum of broilers. A number of 240 male Ross 308 broilers were distributed into four treatments, with five replicates of 12 bird each. The experimental period was 42 days. Treatments includes: 1) basal diet; 2) basal diet supplemented with an AGP (phospho-flavomycin at 450 mg/kg of diet); 3) basal diet supplemented with a Lactobacillus-containing probiotic (250 mg/kg of diet); and 4) basal diet supplemented with an herbal compound (containing thyme, oregano, chamomile, and peppermint essential oils at 1 g/kg of diet). Body weight (BW) and cumulative feed intake (CFI) were measured weekly. Blood parameters, intestinal morphology, vaccine immunity titers, and intestinal microbial population were measured on day 42. The results showed that probiotic and herbal compound supplementation significantly increased body weight (BW) and decreased feed conversion ratio (FCR) (p<0.05), in comparison with the basal diet. A significant increase in vaccine titers against Avian Influenza, Newcastle disease, and Infectious Bursal Disease were achieved with the treatment with herbal compound supplementation. Herbal compound significantly reduced triglycerides, cholesterol, LDL concentration and ALP, AST and ALT activities and increased the HDL levels in blood serum of chicks (p<0.05). The bacterial load of E. coli, Salmonella and coliforms of the AGP-fed group was significantly lower than those fed the control diet. Significant increases in villus height and decrease in crypt depth and goblet cells were seen in the ileum and jejunum of probiotic-fed broilers (p<0.05). In conclusion, better overall immune status and blood biochemical parameters were obtained with the herbal compound than with the probiotic; however, the performance of broilers fed the prob
