From Diet to Disease: The Role of the Gut Microbiome and Microbial Metabolites in Horses.

Overview

• This article reviews how diet influences the gut microbiome and its metabolites in horses, impacting their health and diseases.
• It highlights the connection between different dietary components, microbial metabolite production, and equine gastrointestinal and metabolic disorders.

Introduction to the Equine Gut Microbiome

• The equine gastrointestinal microbiome is crucial for:
• Digesting feed and extracting energy.
• Regulating the immune system.
• Maintaining the balance and health of the intestinal environment (intestinal homeostasis).
• Microbial metabolites act as functional links between what horses eat, the gut microbes, and the horse’s physiological responses.

Scope and Methodology of the Review

• The review synthesized findings from publications up to June 2026.
• Databases searched included PubMed, Web of Science, Scopus, and Google Scholar.
• The literature was organized based on:
• Different dietary factors: structural carbohydrates, non-structural carbohydrates, proteins, and lipids.
• Microbial metabolite production.
• Associated diseases and possible nutritional interventions.

Key Microbial Metabolites and Their Roles

• Major microbial metabolites discussed include:
• Short-chain fatty acids (SCFAs): Important for gut health and immune modulation.
• Endotoxins: Potentially harmful compounds from bacterial cell walls that can trigger inflammation.
• Bile acid derivatives: Affect fat digestion and microbial composition.
• Tryptophan metabolites: Influence immune responses and gut barrier function.
• Nitrogenous fermentation products: Byproducts of protein breakdown that can have diverse effects.
• These metabolites collectively influence health and can contribute to disease when dysregulated.

Diet-Microbiome-Metabolite Axis and Equine Diseases

• The review outlines how this axis is central in several equine gastrointestinal disorders:
• Colic: A common and potentially serious abdominal condition linked with microbial imbalance.
• Colitis: Inflammation of the colon that can be influenced by microbial metabolites.
• Equine gastric ulcer syndrome: Ulcer formation potentially associated with microbial and metabolite changes.
• Carbohydrate-associated laminitis: A painful hoof disease triggered by rapid fermentation of carbohydrates and metabolite shifts.
• The role of this axis in equine metabolic syndrome and the gut-lung axis is less clear and requires further research.

Microbiome-Targeted Nutritional Interventions

• The review emphasizes innovative nutritional strategies aimed at modulating the gut microbiome to improve equine health such as:
• Adjusting fiber types and levels to promote beneficial microbial populations and metabolite profiles.
• Managing carbohydrate intake to prevent harmful metabolite production and disease onset.
• Incorporating prebiotics and possibly probiotics to enhance microbial balance.
• These interventions hold potential for disease prevention, improved welfare, and enhanced athletic performance through microbiome-informed feeding.

Emerging Multi-Omics Approaches

• The review highlights the use of advanced technologies combining genomics, metabolomics, and other “omics” data to:
• Gain a deeper understanding of microbial function in the equine gut.
• Identify novel metabolic pathways and microbial interactions influenced by diet.
• Develop personalized nutrition plans based on microbiome profiles.

Conclusion

• This narrative review synthesizes evidence supporting a pivotal role of diet in shaping the equine gut microbiome and its metabolites.
• There is strong linkage between dietary composition, microbial metabolism, and the development or prevention of several horses’ gastrointestinal diseases.
• Microbiome-focused nutritional strategies represent a promising approach for supporting horse health and performance.
• Continued advancements in multi-omics research will further enhance understanding and application in equine nutrition and medicine.