One thousand two hundred and fifty sexed day-old broiler chicks obtained from a commercial hatchery were randomly divided into five treatment groups of 250 birds each (negative control, antibiotic and essential oil combination at three levels). Each treatment group was further sub-divided in to five replicates of 50 birds (25 male and 25 female) per replicate. Commercial essential oil combination at three different levels (24 mg, 48 mg and 72 mg) and antibiotic (10 mg avilamycin) per kg were added to the basal diet. There were significant effects of dietary treatments on body weight, feed intake (except at day 42), feed conversion ratio and carcass yield at 21 and 42 days. Body weights were significantly different between the treatments. Birds fed on diet containing 48 mg essential oil/kg being the highest, followed by chicks fed the diet containing 72 mg essential oil/kg, antibiotic, negative control and 24 mg essential oil/kg at day 42, respectively. From 1 to 21 and 1 to 42 days age, feed conversion ratio was significantly improved by the supplementation with 48 and 72 mg essential oil/kg diet. The feed intakes were significantly different between the treatments at 21 days, but there were no significant differences at 42 days. Supplementation of essential oil combination to broiler diet in excess of 48 mg/kg had no additional beneficial effect on body weight, feed intake, feed conversion ratio and carcass yield. Essential oil combination, a feed additive of natural origin, may be considered as a potential growth promoter in broiler production.
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