Effect of dietary supplementation with onion (Allium cepa L.) on performance, carcass traits and intestinal microflora composition in broiler chickens

To examine the effect of onion (Allium cepa L.) as an antibiotic growth promoter substitute on growth performance, carcass traits, and microflora composition in broiler chickens. A total of 192 one-day old mixed sex broiler chicks (Ross 308) were weighed and randomly allocated to four treatment groups, each with 4 replicate pens of 12 chicks. The dietary treatments consisted of the basal diet (control), antibiotic (15 mg virginiamycin/kg), and control+10 or 30 g fresh onions bulb/kg diet. Body weights of broilers were determined at Day 1, 21, and 42, feed intake was determined at the same periods, and feed conversion ratio was calculated accordingly. At Day 42, two birds per replicate were slaughtered for determination of carcass and organ weights. The populations of Lactobacilli spp. and Escherichia coli were enumerated in ileum by conventional microbiological techniques using selective agar media. Dietary supplementation of 30 g/kg onion increased final body weight of broilers at 42 d of age compared to that of the other treatments (P<0.05). Birds fed 30 g onion/kg in the diet had the highest feed intake than other treatments at different growth periods (P<0.05). Feed conversion ratio, carcass yield and internal organ weights were not affected by the dietary treatments at Day 42. The Lactobacilli spp. population in birds supplemented with onion at the level of 30 g/kg significantly was higher than other groups at 42 d of age (P<0.05). The lowest Escherichia coli loads were detected in broilers fed diets containing 15 mg virginiamycin/kg. The Escherichia coli loads significantly decreased in broilers fed diets containing 10 or 30 g onion/kg (P<0.05). In conclusion, the results of the current study indicated that supplementing broiler diet with 30 g onion/kg could induce favorable influences on performance and ileum microflora composition.