Comparison of the effects of four commercially available prescription diet regimens on the fecal microbiome in healthy cats.

Diet significantly influences the gut microbiota, with variations in macronutrient content (proteins, fats, and carbohydrates) and the presence of non-digestible carbohydrates, such as fiber, playing crucial roles in shaping microbial composition. This study investigated the effects of four commercial prescription diets (low-carbohydrate, weight-loss, high soluble fiber, and renal) on the fecal microbiome of five healthy domestic cats using a 4 × 4 Latin square design. Fecal samples were analyzed using Illumina sequencing of the bacterial 16S rRNA gene to assess bacterial community structure and diversity. Results showed that cats fed the renal diet (low protein, high carbohydrate, high fat) were associated with higher relative abundances of the class Actinobacteria, particularly Bifidobacterium. The low-carbohydrate diet was associated with higher relative abundances of Adlercreutzia, Collinsella, and Slackia. The high-soluble fiber diet was associated with a higher relative proportion of Streptococcaceae. In contrast, the renal diet was associated with lower relative abundances of Blautia and Erysipelotrichales. No significant differences were observed in alpha-diversity indices among diets, whereas beta-diversity analysis showed significant differences in microbial community composition among dietary groups. These findings suggest that dietary composition may influence the fecal microbiome in healthy cats. However, given the exploratory design and compositional nature of the sequencing data, these findings should be interpreted cautiously and considered hypothesis-generating.