Effect of dietary oregano (Origanum vulgare L.) essential oil on growth performance, cecal microflora and serum antioxidant activity of broiler chickens

A feeding trial was conducted to investigate the effects of dietary oregano (Origanum vulgare L.) essential oil (OEO) on broiler performance, cecal microflora and serum antioxidant activity. One hundred and eighty (180) 1-day old broiler chicks were randomly divided into four groups. Group I was kept as normal control and received basal diet. Birds of groups II, III and IV were treated with basal diet supplemented with 300, 600 and 1200 mg/kg of OEO. Inclusion of 600 mg/kg of OEO in grower diet significantly increased body weight gain when compared with the control group (P < 0.05). Supplementation of 600 and 1200 mg/kg of OEO significantly improved feed conversion ratio compared with the control group in grower and overall experimental periods (P < 0.05). Although, populations of lactic acid bacteria remained unaffected (P > 0.05), populations of cecal Escherichia coli were significantly lower in 300 and 600 mg/kg OEO supplemented groups in comparison with the control and 1200 mg/kg OEO supplemented groups (P < 0.05). Although, serum antioxidant activity was not significantly affected by the treatments (P > 0.05), antioxidant activity of serum was higher in OEO supplemented groups. In conclusion, OEO exerted growth promoting effects and also displayed potent antibacterial effects against cecal E. coli.Key words: Oregano essential oil, performance, cecal microflora, antioxidant activity