The Influence of Diet Change and Oral Metformin on Blood Glucose Regulation and the Fecal Microbiota of Healthy Horses.
Authors: Ericsson Aaron C, Johnson Philip J, Gieche Lyndsy M, Zobrist Chelsea, Bucy Katie, Townsend Kile S, Martin Lynn M, LaCarrubba Alison M
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Dietary management and metformin are established cornerstones of equine metabolic syndrome treatment, yet their mechanisms of action—particularly via the gut microbiota—remain poorly characterised in horses. This study examined how pasture removal with an all-hay diet, with or without oral metformin supplementation for seven days, altered the faecal microbiota composition in six treated horses compared to 24 pasture-dwelling controls, using 16S rRNA sequencing and oral sugar testing. The most notable finding was a significant expansion of the phylum Kiritimatiellaeota in horses switched to hay-only feeding; because this taxon is phylogenetically related to Verrucomicrobia—which expands in rodents and humans receiving metformin—it may represent the functional equivalent driving metabolic improvements in equine patients. These results suggest that dietary restriction and metformin may exert their therapeutic effects through shared microbiotal pathways, offering a mechanistic framework for understanding why pasture removal and pharmacological intervention both improve insulin sensitivity in susceptible horses. For practitioners managing EMS cases, this work implies that dietary change alone may trigger beneficial microbiota shifts similar to those associated with metformin, potentially explaining why many horses respond well to conservative management before pharmacological intervention becomes necessary.
Read the full abstract on PubMed
Practical Takeaways
- •Removing horses from pasture and switching to all-hay diet triggers predictable microbiota changes that may contribute to improved glucose tolerance, supporting this as a foundation treatment for EMS
- •The microbiota response to diet modification alone appears substantial; longer-term studies needed to determine if metformin adds additional microbiota-mediated benefits
- •Understanding that gut microbiota shifts occur with dietary intervention provides mechanistic insight into why pasture restriction is effective for metabolic syndrome management
Key Findings
- •Diet change from pasture to all-hay resulted in significant expansion of the phylum Kiritimatiellaeota in the fecal microbiota of healthy horses
- •Metformin administration did not produce measurably different microbiota changes compared to diet change alone in this 7-day study period
- •Kiritimatiellaeota expansion mirrors Verrucomicrobia expansion observed in mice and humans treated with metformin, suggesting a cognate microbial response in equine hosts
- •Oral sugar tests were administered to diet-changed horses at one-week intervals to assess glucose regulation changes