Improving egg quality is one of the main objectives of the poultry industry. The objective of this study was to investigate the effects of dietary oregano oil supplementation with different concentrations on the egg quality, intestinal morphology and cecal microbiome of late-phase laying hens. A total of 300 55-week-old Snowy white laying hens were randomly divided into five groups and fed a basal diet (control) or basal diets supplemented with oregano oil at 25, 50, 75 and 100 mg/kg (O25, O50, O75 and O100) over a 100-day period. Compared with the control group, eggshell thickness and eggshell weight were increased significantly in eggs when oregano oil was added (p < 0.05). The highest content of polyunsaturated fatty acids (PUFAs) and C18:2n6c was observed in yolks with 25 mg/kg supplement among 5 groups (p < 0.05). The highest average content of riboflavin in egg yolk and thiamine in egg white was observed in the O25 group (p < 0.05). When the supplemental levels of oregano oil were 25 mg/kg and 50 mg/kg, the selenium and phosphorus content in the egg was significantly increased (p < 0.05). The ratio of villus height to crypt depth (V/C) and villus height of the small intestine was significantly increased compared with the chickens fed the basal diet (p < 0.05). Compared with the control group, the abundance of Megamonas was increased in the O50 group (p < 0.05). The unclassified_o__Bacteroidales in the O25 group were significantly higher than those in the other four groups (p < 0.05). These differential microorganisms were significantly correlated with egg quality characteristics. Dietary supplementation of oregano oil can significantly improve egg quality via gut microbiota alteration in laying hens.

Background: The Tibetan chicken has adapted well to high altitudes genetically after its long-term habitation in the plateau. In this study, we analyzed the selection signal of Tibetan black chickens (TBCs) and discovered genes associated with the characteristics of germplasm. Methods: Whole-genome sequencing (WGS) was used to identify the single-nucleotide polymorphism (SNP) markers and genetic structures in the genome of Tibetan black chickens. Further, we performed a comparative population genomics analysis between the genomic data obtained in this present study and the genomic data for five wild red jungle fowls (RJFs) accessed from the NCBI database (GenBank accession number PRJNA241474). Thereafter, the Fst and Pi selections were used to identify genes under positive selection in the Tibetan black chicken genome. Results: A total of 9,490,690 SNPs were identified in the Tibetan black chickens. In addition, the results from the gene ontology (GO) analysis showed that 732 genes of TBCs were enriched in a total of 210 GO terms with specific molecular functions such as regulation of cellular catabolic process, the MAPK signaling pathway, regulation of ion transport, growth, morphogenesis and lung alveolus development which may provide a better mechanism to facilitate oxygen transport and utilization in TBCs. Moreover, the results from the KEGG analysis showed that 732 genes of the TBCs were significantly enriched in the calcium signaling pathway, circadian entrainment (ADCY1, GNG7 and PER3), oxytocin signaling pathway and pathways of multiple neurodegeneration diseases. In addition, the CD86 antigen (CD86) was identified as a gene associated with the immune response in chickens. It was also revealed that genes such as TRIT1, HPCAL4, NT5C1A and HEYL were discovered under selection in Tibetan black chickens on chromosome 23. These genes may be related to the local adaptive characteristics of Tibetan black chickens, for instance, NT5C1A and HEYL may be involved in the high-altitude adaption of oxygen delivery in Tibetan black chickens. Conclusions: In summary, we found that selection mainly affects the disease resistance and cold acclimatization of Tibetan black chickens. Hence, these results may provide important genetic information for the evolution and breeding of Tibetan black chickens.

This study comprehensively investigated the effects of different dietary energy levels—low energy (LE, 10.62 MJ/kg), medium energy (ME, 11.87 MJ/kg), and high energy (HE, 13.06 MJ/kg)—on growth performance, meat quality, muscle metabolite profiles, and cecal microbiota in a local Chinese chicken breed (Guangyuan gray chicken). Growth and carcass traits, including interpubic width and liver weight, responded positively to increasing dietary energy. Compared to the ME control, the HE diet significantly increased drip loss, whereas the LE diet reduced both intramuscular fat and protein content ( P <0.05). Untargeted metabolomic analysis identified 188 differentially abundant muscle metabolites across the dietary groups, revealing distinct metabolic profiles. The biosynthesis of the amino acids pathway was significantly affected by different dietary energy levels. Targeted metabolomics further demonstrated the differences in muscle amino acid composition: essential, sweet-taste, and umami-taste amino acids increased progressively with dietary energy, with the HE group achieving the most favorable profile for flavor and nutrition. Cecal microbiota analysis indicated that dietary energy levels significantly altered microbial community structure. Specific bacterial taxa, including Spirochaetota and Bacteroides , were positively correlated with muscle amino acid concentrations. Our findings demonstrate that dietary energy level modulated the cecal microbiota, which in turn influenced muscle amino acid deposition and overall meat quality. This study provides a comparative multi-omics perspective for optimizing dietary energy strategies in local chicken production to meet varying market demands for meat quality and nutritional value. IMPORTANCE: This comparative study established a crucial link between dietary energy intake and the final quality of poultry meat through a multi-omics lens. We demonstrate that low, medium, and high dietary energy levels elicit distinct phenotypic, metabolic, and microbial profiles in a local chicken breed. The findings provide a scientific framework for selecting dietary energy strategies tailored to specific market demands: HE for premium quality segments, LE for lean or cost-driven production, and ME for efficient conventional production. We identified specific correlations between the cecal bacteria ( Spirochaetota , Bacteroides ) and muscle metabolites (key amino acids). Thus, this work offered the scientific data to optimize meat quality through targeted feeding interventions.