Essential oils alleviate coccidiosis impact in broiler chickens: a meta-analysis

Objective: This meta-analysis aims to examine the efficacy of essential oils (EO) as an anticoccidial alternative on broiler chickens under coccidia challenged trials, focusing on performance indicators including average daily gain (ADG), feed intake (FI), feed conversion ratio (FCR), final body weight (BW), mortality, and intestinal lesion. Methods: A random-effects model was performed using the metafor package in R software. In a subgroup meta-analysis, treatment groups including coccidia-infected birds [C+], C+ group treated with EO [C+EO] or antibiotics [C+AB], and a non-infected control group treated with EO or AB, were compared against the control group [CON]. Results: As expected, C+ birds had lower (p<0.001) final BW and ADG as well as higher (p<0.001) FCR. Administration of either EO or AB on birds with coccidiosis infection resulted in similar final BW, ADG, FI, and FCR with CON birds, suggesting the comparable effectiveness of EO and AB to alleviate the adverse effects of coccidiosis. Broilers on the C+ group exhibited increased small intestine damage as shown by the greater (p<0.001) lesion score, but the mortality was not different from CON and other treatment groups. The Eimeria oocyst count was lower on birds treated with EO than on the infected birds, with an average suppression of 42.11%. Meta-regression demonstrated that C+ birds had inferior FI and ADG than CON and C+EO birds. However, high heterogeneity between studies was identified in all measured outcomes as shown by I²>75%, suggesting wide variability among study conditions. Conclusion: EO may serve as an alternative antibiotic to mitigate the negative impacts of coccidiosis infection in broiler chickens.