Dietary supplementation with blended essential oils improves meat quality of broilers through SCFA-mediated gut-muscle axis

This study aims to evaluate the effects of a commonly used blended essential oils (EOs, composed of thymol, carvacrol, and cinnamaldehyde) on the growth performance and meat quality of Pectoralis major (breast muscle) in broilers, as well as the role of the gut microbiota-muscle axis in this process. Sixty 7-day-old Arbor Acres male broilers were divided into two dietary treatment groups (6 replicate pens per group and 5 broilers per pen) and raised for 35 d. The control group (Con) of broilers was fed a basal diet, while the EOs group was provided with a basal diet supplemented with a complex EOs of cinnamaldehyde (200 mg/kg), carvacrol (200 mg/kg), and thymol (100 mg/kg). Hematoxylin and eosin staining was used for histomorphological evaluation. To analyze the composition of the gut microbiota, 16S rRNA sequencing was performed. Short-chain fatty acids (SCFA) were quantified via GC-MS-based targeted metabolomics. Gene and protein expression levels were analyzed by qRT-PCR, Western blotting, and immunofluorescence. The results indicated that EOs supplementation enhances the growth performance of broilers by increasing their feed intake (P < 0.01). Importantly, EOs promoted meat quality by improving the meat color (P < 0.01) and shear force (P < 0.001). Moreover, EOs facilitated the intestinal development, as evidenced by the increased ratio of villus height to crypt depth (P < 0.05). Further analysis revealed that EOs supplementation elevated serum levels of acetic acid and propionic acid (P < 0.001) by increasing the abundance of beneficial microbiota responsible for SCFA production. Acting as mediator of the gut-muscle axis, SCFA promoted breast muscle fiber development by activating the IGF-1/AKT/mTOR signaling pathway (P < 0.05); concurrently, microbiota-derived SCFA induced by EOs activated the Keap1/Nrf2/HO-1 antioxidant defense system (P < 0.05), thereby mitigating oxidative stress and ultimately improving the meat quality of broiler breast muscle. In summary, our findings provide the first evidence that dietary supplementation with blended EOs improves broiler meat quality via a SCFA-mediated gut-microbiota-muscle axis.