Nutrition, Prebiotics, Probiotics, and Postbiotics for Canine and Feline Gut Health and Behaviour: A Critical Review and Research Agenda

The gut microbiome is integral to the health of both dogs and cats, influencing nutrient metabolism, immune function, and even behaviour through the gut-brain axis (GBA). This critical review synthesizes current data on microbiota-targeted interventions—including prebiotics, probiotics, and emerging postbiotics—for managing common conditions in companion animals. We systematically evaluate the evidence, highlighting strong support for gastrointestinal applications, such as acute diarrhea, while also examining the reasons for inconclusive findings in obesity, allergic skin disease, and behavioral outcomes. A significant barrier to progress is the marked heterogeneity in study designs, strains, and outcome measures, compounded by a critical scarcity of feline-specific data. Standardized trials and stricter product quality regulation are strongly warranted. To advance from promising to proven therapies, the field must embrace rigorous, evidence-based, and potentially personalized approaches. The take-home message for clinicians is to confidently use probiotics for diarrhea, while remaining cautious about their use for other chronic conditions until more robust, species-specific data emerge.