El objetivo del presente trabajó de investigación fue evaluar el efecto de un ácido orgánico (Acido fumárico) y un prebiótico comercial (Fortifeed®), y la combinación de éstos frente a un antibiótico promotor de crecimiento (Bacitracina de Zn) y un control, en el alimento de pollos de engorde, determinando los parámetros productivos y salud intestinal.//Abstract: The objective of this experiment was to study effect of a organic acid (Fumaric acid) and a commercial prebiotic ( Fruto-oligosaccharides Fortifeed®) alone and combined, compared with antibiotic (Zn Bacitracin) in the productive performance, cost, the digestive tract morphology (intestinal villus morphometry), allometric growth of the digestive system, and bacterial analysis of the ileum (E. coli, coliform and aerobic mesophilic bacteria). The five dietary treatments were: a basal diet (negative control), antibiotic (Zn Bacitracin 0,3 g/kg), 5 g/kg Fumaric acid (organic acid), 0,6 g/kg fructooligosaccharides FOS (prebiotic) and 5 g/kg fumaric acid + 0,6 g/kg FOS. Each treatment consisted of four pens. The data were analysed using InfoStat software program (by one-way analysis of variance, and significant differences between treatments were determined by Tukey test). Three bioassays were designed: A with male Hybro broiler chickens measurements productive performance and cost, another with male Cobb broilers chickens measurements productive performance, cost and allometric growth of the digestive system with controlated feed from 1 to 42 days of age. The birds give antibiotic, prebiotic and combinations of the prebiotic with either organic acid had better daily live weight and feed conversion ratio (FCR) compared to treatment control and organic acid beening better to the prebiotic in broilers cobb. The mortality was not different in two broilers (Hybro and Cobb).