Biology

Feed conversion ratio

Animal science

Cecum

Endocrinology

Dry matter

Food science

Environmental health

Gizzard

Body weight

Feed additive

Population

Internal medicine

Medicine

Chemistry

Broiler

Animal Bioscience

Objective: The purpose of this meta-analysis was to evaluate the effect of dietary essential oils (EOs) on productive performance, nutrient digestibility, and serum metabolite profiles of broiler chickens and to compare their effectiveness as growth-promoting additives against antibiotics.Methods: Peer-reviewed articles were retrieved from Web of Science, Science Direct, PubMed, and Google scholar and selected based on pre-determined criteria. A total of 41 articles containing 55 experiments with 163 treatment units were eligible for analyses. Data were subjected to a meta-analysis based on mixed model methodology considering the doses of EOs as fixed effects and the different studies as random effects.Results: Results showed a linear increase (p&lt;0.001) on body weight gain (BWG) where Antibiotics (FCR) and average daily feed intake decreased (p&lt;0.001) linearly with an increasing dose of EOs. Positive effects were observed on the increased (p&lt;0.01) digestibility of dry matter, crude protein, ether extract, and cecal Lactobacillus while Escherichia coli (E. coli) population in the cecum decreased (p&lt;0.001) linearly. There was a quadratic effect on the weight of gizzard (p&lt;0.01), spleen (p&lt;0.05), bursa of fabricius (p&lt;0.001), and liver (p&lt; 0.10) while carcass, abdominal fat, and pancreas increased (p&lt;0.01) linearly. The dose of EOs linearly increased high density lipoprotein, glucose, protein, and globulin concentrations (p&lt;0.01). In comparison to control and antibiotics, all type of EOs significantly reduced (p&lt;0.001) FCR and tended to increase (p&lt;0.1) BWG and final body weight. Cinnamaldehyde-compound was the only EOs type showing a tendency to increase (p&lt;0.1) carcass weight, albumin, and protein of serum metabolites while this EOs together with EOs-Blend 1 decreased (p&lt;0.01) E. coli population. Low density lipoprotein concentration decreased (p&lt;0.05) with antibiotics and carvacrol-based compound when compared to the control group.Conclusion: This evidence confirms that EOs are suitable to be used as growth promoters and their economical benefit appears to be promising.

Essential oils as growth-promoting additives on performance, nutrient digestibility, cecal microbes, and serum metabolites of broiler chickens: a meta-analysis