At 21 d of age BW of chicks did not differ (P >0.05) between the dietary treatments, although BW of broiler supplemented with 30 g onion/kg was higher than other groups. At the end of the trial (d 42), birds supple- mented with the 30 g onion/kg had a greater BW com- pared with other groups (P < 0.05). The average daily feed intake (from d 1 to 21) was increased (P < 0.05) for bird supplemented with 30 g onion/ kg of diet. The av- erage daily feed intake (ADFI) during grower and the entire experimental period was higher for broilers sup- plemented with 30 g onion/kg compared with control birds and birds supplemented with antibiotic (P < 0.05). Broilers receiving 10 or 30 g onion/ kg had a lower feed conversion ratio (FCR) compared to broilers receiving antibiotic during the starter period (P < 0.05), but FCR of broilers in other periods was not affected. No differences because of treatment effects were observed on mortality.