Abstract
This study assessed the impacts of essential oils (EOs) consisting of 4.5 g cinnamaldehyde and 13.5 g thymol per 100 g of EOs as phytogenic growth promoters in broiler diet. A total of 216, one-day-old male Arbor Acres broiler chickens were randomly allotted into six groups, each with six replicates. The 1st group was fed a basal diet (Control) without supplementation; the 2nd group was fed the basal diet including zinc bacitracin (ZnB); the 3rd, 4th, 5th and 6th groups were fed the basal diet including EOs at 25 (EOs_25), 50 (EOs_50), 100 (EOs_100) and 150 (EOs_150) mg/kg diet, respectively. The group EOs_150 showed significantly increased (p < .05) body weight gain (BWG), enhanced feed conversion rate (FCR) and production efficiency index (PEI) compared to the other groups, except for EOs_100. Increasing concentrations of EOs above 25 mg/kg significantly (p < .05) increased protein, lipid and fibre digestibility; the addition of EOs also increased the amount of edible parts and dressing percentage of carcases. Diets EOs_100 and EOs_150 resulted in significantly increased plasma total protein and globulin levels, while EOs_150 led to higher plasma glucose concentrations. From the findings, supplementation with 100 mg/kg EOs in encapsulated, heat-stable forms could be used as an alternative growth promoter to ZnB in broiler chickens.
Highlight
* Essential oils can replace antibiotic in broiler nutrition with no adverse effects on growth performance.
* Essential oils improved total edible parts and dressing percentage.
* Essential oils enhanced digestibility of protein, lipid and fibre. Thus essential oils contained of 4.5 g cinnamaldehyde and 13.5 g thymol per 100 g can be used at 100 mg/kg feed as alternative growth promoter for broilers chickens.