ObjectiveThis study was conducted to investigate the effect of dietary onion (Allium cepa) extract (OE) supplementation on growth performance, apparent total tract retention (ATTR), blood profile, carcass characteristics and meat quality in broilers.MethodsFour hundred male broiler chicks (Ross 308, 3-d old) were randomly allocated to four dietary treatments for 28 d feeding trial. Each treatment has five replications with 20 birds each. Four dietary treatments were designated according to the OE supplementation levels (0 as control, 5, 7.5, and 10 g of OE per kg of basal diet respectively). On d 28, a total of 20 birds from each treatment were subjected for ATTR, serum biochemical assay, carcass characteristic and organ weight measurement.ResultsOverall weight gain of OE 7.5 g/kg group was higher (p = 0.04) than control group. The ATTRs of dietary energy (p<0.01) and ether extract (p = 0.04) linearly increased with increasing levels of dietary OE. However, no difference in ATTR of dry matter and crude protein was evident. Furthermore, serum IgG concentration increased linearly (p<0.01) and quadratically (p = 0.03) with increasing OE supplementation. No differences in carcass dressing weight and amount of abdominal fat by treatments were observed. Also, the weight of organ including immune organ was not different among the treatments. The TBARS values of 10 d stored breast meat decreased linearly (p<0.01) and quadratically (p<0.01) with increasing dietary OE levels. The meat color was also affected, with lower (p<0.01) redness score in meats from OE supplemented groups. This study showed that dietary OE improved broiler weight gain presumably by increasing feed intake and ATTR of both energy and ether extract. The dietary OE increased serum IgG level and meat anti-oxidation capacity.ConclusionThis study implies that the recommended level of dietary OE supplementation could be beneficial for improving broiler performance and meat quality.