ABSTRACT A total of 350-one-day old chicks were placed in 70 cages, with 14 cages per treatment. The following five treatment diets were fed for 14 days: T1 = non-supplemented, control diet (CONT); T2 = diet with antimicrobial growth promoter (AGP); T3 = diet with a probiotic (PROB); T4 = diet with a prebiotic(PREB), and T5 = diet with the probiotic and the prebiotic (SYM). The growth experiment was carried out from 1 to 14 days of age. Feed and water were provided ad libitum and birds were maintained at 24-h light schedule. Diets were formulated to contain 3000 kcalME/kg and 21.5% crude protein, and the test materials were added on top. The cumulative results of1 to 14 days of age revealed that broiler fed the AGP and PREB diets presented the highest BWG (305.5 and 297.3 g, respectively), while those fed the CONT diet had the lowest BWG (273.2 g) (p<0.05). On the other hand, the best FCR was obtained in broilers AGP and PROB (1.296 and 1.299 g:g, respectively), while chicks on the CONT and SYM diet had the worst FCR (1.423 and 1.372 g:g, respectively) (p<0.01). The results showed broilers fed the non-supplemented diet consistently presented poor performance. It was concluded that PROB or PREB can serve as alternatives to antibiotic in broiler starter feeds, with no performance impairment.