Abstract
OBJECTIVE: This study aimed to characterize the fecal microbiome of highly productive laying hens to identify microbial signatures linked with enhanced egg production performance. METHODS: Six commercial layer farms were enrolled in the study. Farms with an average monthly egg production rate (amEPR) above 80% over six consecutive months were classified as the high-production group (D group; n = 3), while those with amEPR below 60% were designated as the low-production group (P group; n = 3). All hens were raised in open-type housing systems without a history of forced molting. From each farm, 36 fecal samples were randomly collected and subjected to full-length 16S ribosomal RNA gene sequencing to characterize the microbiome. RESULTS: The D group showed significantly higher Firmicutes-to-Bacteroidetes ratios (p<0.001) and lower species richness (Menhinick index, p<0.05) compared with the P group. Multivariate analyses (Adonis, ANOSIM, and MRPP; all p<0.001) revealed distinct microbial community structures between the groups. Taxonomic profiling indicated that the D group harbored higher relative abundances of Enterococcus cecorum and Lactobacillus kitasatonis (both p<0.05). In contrast, the P group had elevated levels of Bacteroides eggerthii and Bacteroides coprosuis (p<0.001 and p<0.05, respectively). Principal component analysis and linear discriminant analysis effect size further identified Enterococcus cecorum and Lactobacillus kitasatonis as biomarkers associated with superior egg production. In Hy-Line hens, Lactobacillus gallinarum and Lactobacillus salivarius were also identified as biomarkers linked to high productivity. CONCLUSION: The fecal microbiome of highly productive laying hens is characterized by an enrichment of Enterococcus cecorum and lactic acid bacteria, particularly Lactobacillus kitasatonis, Lactobacillus gallinarum, and Lactobacillus salivarius. Their targeted supplementation may represent a promising probiotic strategy to improve egg production efficiency in commercial laying hens.