Dietary encapsulated fennel seed (Foeniculum vulgare Mill.) essential oil supplementation improves performance, modifies the intestinal microflora, morphology, and transcriptome profile of broiler chickens

Global antimicrobial resistance has led to a ban on the use of antibiotics as growth promoters (AGPs) in poultry farming, encouraging the use of natural phytogenic feed additives that provide similar effects to AGPs without causing resistance. The aim of this study was to determine the effects of the addition of encapsulated fennel seed (Foeniculum vulgare Mill.) essential oil (FEO) into the diets on the performance, intestinal microflora, morphology, and transcriptomic profiling of broiler chickens. In the study, 400 one-d-old male chicks of the Ross-308 genotype were randomly distributed into five groups, each with 16 replicates of five birds. The experiment included a control group fed on basal diets without the addition of FEO and treatment groups supplemented with 50 (FEO50), 100 (FEO100), 200 (FEO200), or 400 (FEO400) mg of encapsulated FEO/kg. Body weight and the European Production Efficiency Factor values were higher in the FEO100, FEO200, and FEO400 groups (P