Here, molecular pathways and genes involved in the feed efficiency (FE) and thigh-meat quality of slow-growing Korat chickens were investigated. Individual feed intake values and body weights were collected weekly to the calculate feed conversion ratios (FCR) and residual feed intake. The biochemical composition and meat quality parameters were also measured. On the basis of extreme FCR values at 10 weeks of age, 9 and 12 birds from the high and the low FCR groups, respectively, were selected, and their transcriptomes were investigated using the 8 × 60 K Agilent chicken microarray. A weighted gene co-expression network analysis was performed to determine the correlations between co-expressed gene modules and FE, thigh-meat quality, or both. Groups of birds with different FE values also had different nucleotide, lipid, and protein contents in their thigh muscles. In total, 38 modules of co-expressed genes were identified, and 12 were correlated with FE and some meat quality traits. A functional analysis highlighted several enriched functions, such as biological processes, metabolic processes, nucleotide metabolism, and immune responses. Several molecular factors were involved in the interactions between FE and meat quality, including the assembly competence domain, baculoviral IAP repeat containing 5, cytochrome c oxidase assembly factor 3, and myosin light chain 9 genes.

The aim of this study was to investigate the expression of mitochondrial oxidative phosphorylation (OXPHOS) genes, oxidative stress, and antioxidant responses in the duodenum, involved in differential residual feed intake (RFI), an indicator of feed efficiency. The study was conducted on two groups of 15 male slow-growing Korat chickens (KRC), the low RFI (LRFI) group and the high RFI (HRFI) group, with mean values of -197.8 ± 12.1 g and 200.8 ± 15.1 g, respectively. The results indicated that differences in RFI did not negatively affect growth performance (P>0.05). The LRFI group had a significantly lower feed intake than the HRFI group (P<0.05). Expression profiles of mitochondrial OXPHOS genes showed that COX1, COX2, COX3, CYTB, ND2, ND5, ATP6, and ATP8 were upregulated in HRFI chickens (P<0.05), indicating a higher mitochondrial activity related to cellular respiration for energy production. This was consistent with the higher oxidative stress indicated by increased reactive oxygen species (ROS) production observed in HRFI chickens. Moreover, the antioxidant enzyme activities in HRFI were significantly higher than those in LRFI, suggesting that HRFI birds have the capacity to cope with elevated levels of ROS. Principal component analysis (PCA), which integrated phenotypic characterization, mitochondrial oxidative status, and gene expression levels, revealed a clear separation between LRFI and HRFI chickens, with PC-1 explaining 47% of the variance. Mitochondrial OXPHOS genes and oxidative stress-related traits clustered toward the HRFI group, indicating a positive correlation between reduced feed efficiency, oxidative metabolism to produce energy, and elevated oxidative stress. This study demonstrates that differences in feed efficiency in KRC were associated with differences in mitochondrial function related to cellular respiration and antioxidant enzyme mechanisms, which eliminate ROS produced during cellular respiration. The findings suggested that HRFI chickens had greater energy demands compared to LRFI chickens.

Improving feed efficiency (FE) in slow-growing Korat chickens (KRC) is crucial for enhancing productivity and reducing production costs for sustainability. This study aimed to investigate the expression of genes and proteins involved in glycolysis and oxidative stress pathways and to identify potential metabolic biomarkers associated with residual feed intake (RFI). A total of 30 male KRCs were selected based on extreme RFI values at 10 weeks of age, forming low-RFI and high-RFI groups (n = 15/group). Duodenal samples were collected to extract total RNA and protein. Gene expression levels of Aldolase C (ALDOC), Lactate Dehydrogenase B (LDHB), Phosphoglycerate Mutase 1 (PGAM1), Triphosphate Isomerase (TPI1), Superoxide Dismutase 1 (SOD1), and Peroxiredoxin-1 (PRDX1) were analyzed using real-time quantitative PCR, while protein levels of LDHB and SOD1 were analyzed by Western blot. Plasma glucose, pyruvate, and protein carbonyl content were also measured. Low-RFI chickens exhibited significantly higher mRNA and protein expression of LDHB, as well as elevated TPI1 mRNA levels (P < 0.05). Conversely, HRFI chickens showed increased expression of SOD1 at both mRNA and protein levels, along with significantly higher plasma glucose and protein carbonyls and lower pyruvate concentrations (P < 0.05). Principal Component Analysis (PCA) revealed a clear separation between RFI groups, with the LDHB gene associated with the low-RFI group. Whereas the SOD1 gene and SOD1 protein, along with plasma glucose and protein carbonyl content, were positively correlated with the high-RFI group. These findings suggest that LDHB and SOD1 genes may serve as potential biomarkers for FE, reflecting differences in energy metabolism and oxidative stress response in slow-growing chickens. This highlights the potential application of these markers in genetic selection and nutritional strategies to improve FE in poultry.

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.

Korat chicken (KRC), a slow-growing chicken known for its unique meat flavor and nutritional value, exhibits variation in feed efficiency (FE). Since the hypothalamus acts as a convergent and integrative center for multiple nutrient-related signals, this study aims to compare transcriptomic profiles and neuronal pathways in hypothalamus between two groups of male KRCs differing in residual feed intake (RFI). RNA was extracted from hypothalamic tissues of males KRC either in the low-RFI (n = 10) or in the high-RFI (n = 10) group. The results showed 257 DEGs, including 138 upregulated and 119 downregulated genes in the low RFI compared to the high-RFI groups. Gene Ontology analysis of the DEGs revealed that they were mainly related to metabolic processes and transporter activity. Kyoto Encyclopedia of Genes and Genomes pathway analysis identified 3 significant pathways, including the folate biosynthesis (3 genes including GCH1, TPH2, and TH), tyrosine metabolism (3 genes including DDC, TH and FAH), and tryptophan metabolism (3 genes including DDC, TPH2, and TDO2) pathways. The upregulated genes in the low-RFI group (TPH2, DDC, and TH) were enriched in the folate biosynthesis, tyrosine metabolism, and tryptophan metabolism pathways, which is consistent with the observed plasma concentrations of dopamine (DA) and serotonin/5-hydroxytryptamine (ST/5-HT). These findings suggest that differences in DA and ST/5-HT levels among the chicken groups may be associated with variation in FE. Furthermore, genes such as GCH1, TPH2, DDC, TH, and FAH could be candidate genes supporting the role of hypothalamus in regulating FE of slow-growing KRC.