Dietary Oregano Essential Oil Supplementation Combined with Cinnamaldehyde Improves Production Performance and Alters Gut Microbiota in Late-Phase Laying Hens

Background: Essential oils (EO) have the characteristics of antibacterial and anti-inflammatory, and are called natural antibiotics. This study was aimed to investigate the potential effects of EO on production performance, egg quality, fatty acid composition in yolk and cecum microbiota of hens in the late phase of production. A total of 350 58-week-old Jing Tint 6 laying hens were randomly divided into 5 groups: 1) a basal diet (control); 2) a basal diet + 5 mg/kg flavomycin (AGP); 3) a basal diet + 100 mg/kg oregano essential oil (OEO) + 20 mg/kg cinnamaldehyde (EO1); 4) a basal diet + 200 mg/kg oregano essential oil + 20 mg/kg cinnamaldehyde (EO2); 5) a basal diet + 300 mg/kg oregano essential oil + 20 mg/kg cinnamaldehyde (EO3). Results: Compared to the control group, EO2 group resulted in a higher (P < 0.05) egg production during weeks 5-8 and 1-8. EO2 group had a lower feed conversion ratio than control group during weeks 1-8. The content of monounsaturated fatty acid (MUFA) in EO2 group is higher (P < 0.05) than that of control and AGP groups. EO2 group increased (P < 0.05) the abundance of Actinobacteriota and decreased the abundance of Desulfovibri in cecum. The abundances of Anaerofilum, Fournierella , Fusobacterium and Sutterella were positively correlated with egg production, feed conversion ratio, and average daily feed intake, while the abundances of Bacteroides , Desulfovibrio , Lactobacillus , Methanobrevibacter , and Rikenellaceae_RC9_gut_group were negative correlated with egg production, feed conversion ratio, and average daily feed intake. Conclusions: Dietary OEO at 200 mg/kg and cinnamaldehyde at 20 mg/kg addition could improve the egg production performance, decrease feed conversion ratio and alter the egg fatty acid and microbial composition of late-phase laying hens.