Cross-sectional analysis of feline gut microbiota reveals differences across age-defined groups under varying environments

The gut microbiome plays a critical role in host health; however, its variation across age groups in domestic cats ( Felis catus ) remains unclear. This study characterized differences in the feline gut microbiota using 16S rRNA gene sequencing in 83 cats across five age-defined groups under varying environments: Pre-weaning (1.5 months, n = 16), Early kitten (3 months, n = 16), Late kitten (6–10 months, n = 15), Young adult (2 years, n = 20), and Mature adult (7–10 years, n = 16). Significant differences in microbial diversity and composition were observed across groups. Alpha-diversity was lowest in Pre-weaning kittens, peaking in Young adults, and declining in Mature adults. Beta-diversity revealed distinct clustering among groups (PERMANOVA, R 2 = 0.33, p = 0.001). Sensitivity analysis excluding the heterogeneous Mature adult group showed consistent patterns and increased the explanatory power of age ( R 2 = 0.48). At the taxonomic level, Pre-weaning microbiota were enriched in Proteobacteria, particularly Escherichia-Shigella . Following weaning, the relative abundance of Negativibacillus increased, whereas Lactobacillus decreased. Bifidobacterium was more abundant in kitten stages, while Faecalibacterium exhibited higher abundance in Young adults. These patterns were generally consistent in sensitivity analyses. In contrast, the Mature adult group exhibited reduced Prevotella and increased Escherichia-Shigella relative to Young adults. Overall, this cross-sectional study identified compositional differences in the feline gut microbiota across age-defined groups under varying environments. These findings should be interpreted as group-level associations rather than independent age effects. Further controlled and longitudinal studies are needed to disentangle these effects.