Combination of Cinnamaldehyde with Carvacrol or Thymol Improves the Mechanical Properties of Tibia in Post-Peak Laying Hens

SIMPLE SUMMARY: In the current study, the roles of dietary cinnamaldehyde, carvacrol, and thymol blend in the tibia characteristics in post-peak laying hens were evaluated. We firstly analyzed the tibia bone properties and demonstrated that a diet supplemented with a 100 mg/kg combination of cinnamaldehyde with carvacrol or thymol could increase the strength of tibia in layers. We also found that the role of dietary essential oils enhanced intestinal barrier, decreased systemic inflammation, and reduced bone resorption marker in serum. These data indicated that a diet with a blend of cinnamaldehyde and carvacrol or thymol could improve the mechanical properties of tibiae for laying hens, in which enhancing intestinal barrier and decreasing systemic inflammation might be a key mediator. ABSTRACT: Roles of plant-derived cinnamaldehyde, carvacrol, and thymol in the gut and bone health of laying hens was evaluated in the present study. After acclimation for 2 weeks, a total 384 of 52-week-old laying hens were allocated into three groups for 6 weeks: (1) basal diet group (Ctrl), (2) combination of cinnamaldehyde with carvacrol group (CAR+CIN), and (3) blend of cinnamaldehyde with thymol (THY+CIN). The dietary essential oil level was 100 mg/kg. Each treatment group had eight replicate pens (16 birds/pen). The stiffness and ultimate load of the tibiae from both the CAR+CIN and THY+CIN groups were higher than that of the Ctrl group (p < 0.05), along with comparable tibia ash, calcium, and phosphorus content among groups. At the same time, the manipulation of essential oils upregulated the transcription abundances of intestinal barrier proteins to varying degrees, whereas the experimental treatment failed to affect the composition in phyla of cecal microbiota. When compared to the Ctrl group, birds fed the CAR+CIN and THY+CIN diet displayed decreased bone resorption markers, reduced interleukin-1 concentrations, and increased transforming growth factor beta levels in serum. These findings suggest that cinnamaldehyde with carvacrol or thymol in feed of hens could enhance intestinal barrier and improve the mechanical properties of tibiae through structural modelling but not increase the mineral density, which might be involved in suppressing inflammation-mediated bone resorption.