Effects of oregano extracts, alone or in combination with other biomolecules, on growth performances and parasitological parameters of broiler chickens challenged with Eimeria spp.: a meta-analysis.

Avian coccidiosis, caused by Eimeria protozoa, remains a major constraint in poultry production, prompting the search for alternatives to conventional anticoccidial drugs. Phytogenic feed additives, particularly oregano (Origanum vulgare) extracts rich in carvacrol and thymol, have emerged as promising candidates. This meta-analysis assessed the effects of dietary oregano supplementation, used alone or combined with other additives, on performance and parasitological outcomes in broiler chickens experimentally infected with Eimeria species. A systematic search identified eight studies published between 2003 and 2023, providing 16 independent comparisons. Four outcomes were analyzed: body weight (BW), feed conversion ratio (FCR), oocyst output per gram of faeces (OPG), and intestinal lesion scores (LS). Pooled estimates were generated using a random-effects model. Heterogeneity was evaluated using the I² statistic and Q-test, while publication bias was assessed with funnel plots and Egger's regression. Oregano supplementation significantly improved all parameters, with pooled effects of +19.9% for BW, -9.2% for FCR, -27.1% for OPG, and -31.0% for LS. Although heterogeneity was high (I² >90%, P < 0.0001), no significant publication bias was detected (Egger's P > 0.05). Sensitivity analyses confirmed result robustness. Overall, oregano extract supplementation (100-300 mg/kg) enhances growth performance and reduces parasitological burden in Eimeria-challenged broilers, supporting its use as a natural alternative, though further studies are needed to optimize dosage and confirm efficacy under commercial conditions. These findings highlight the potential integration of phytogenic additives into sustainable poultry health strategies and encourage large-scale field trials to validate consistency, economic benefits, and long-term impacts on resistance development and animal welfare.