Impact of residual feed intake on jejunal tight junction morphology and gene expression in slow-growing Korat chickens.

Improving feed efficiency (FE) in Korat chickens (KRC), a Thai slow-growing breed, is essential for reducing production costs. This study aimed to investigate gene and protein expression related to oxidative phosphorylation and tight junction pathways, as well as jejunal tight junction morphology in KRC with divergent residual feed intake (RFI). A total of 115 male KRC was raised individually and fed in three phases (starter, grower, and finisher). At 10 wk, RFI was calculated and used to select low-RFI (LRFI) and high-RFI (HRFI) groups (n = 15/group). Gene and protein expression were analyzed by real-time quantitative PCR and Western blot, respectively. Tight junction morphology was examined by Transmission Electron Microscope technique. LRFI chickens showed significantly lower RFI and FCR than HRFI chickens (P < 0.05) and exhibited upregulated expression of tight junction-related genes: Actinin Alpha 1 (ACTN1), Tubulin Alpha 3E (P < 0.05), while oxidative phosphorylation-related genes showed no significant differences. Additionally, the LRFI group demonstrated significantly higher ACTN1 protein expression (P < 0.05). Morphological analysis revealed that the LRFI group exhibited more compact and structurally intact tight junctions. These results indicate that improved intestinal barrier function and nutrient absorption in LRFI chickens may contribute to enhanced FE, highlighting their potential for genetic improvement in slow-growing chickens.