Fecal Microbiome Responses to Sudden Diet Change in Mangalarga Marchador horses.
Authors: Franzan Bruna Caroline, Coelho Irene da Silva, de Souza Marina Torres, Santos Marina Monteiro de Moraes, de Almeida Fernando Queiroz, Silva Vinicius Pimentel
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Fecal Microbiome Responses to Sudden Diet Change in Mangalarga Marchador horses Sudden dietary transitions in horses risk triggering gastrointestinal upset, yet the underlying microbial mechanisms remain incompletely characterised. Franzan and colleagues used a crossover design with eight horses, establishing them on either Coastcross hay alone or complete extruded diet for 34 days before abruptly switching groups and sampling faeces at 24 and 96 hours post-change. Horses switched to extruded feed showed rapid microbiome disruption—alpha diversity dropped within 24 hours alongside decreased Firmicutes and increased Bacteroidetes, with further shifts by 96 hours including reduced pH and Verrucomicrobia expansion. Conversely, horses returning to hay-only feeding demonstrated more resilience, with only transient changes at 24 hours that largely resolved by 96 hours. The asymmetrical response between diet transitions underscores that extruded concentrates provoke more pronounced dysbiosis than forage, information that should inform gradual introduction protocols and help clinicians anticipate which dietary changes carry highest colic or acidosis risk in practice.
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Practical Takeaways
- •Sudden diet changes cause measurable microbiome disruption within 24-96 hours; allow gradual transition periods when possible to minimize GI upset risk
- •Horses transitioning from hay-based to complete extruded diets show greater microbiome shifts than the reverse, suggesting different digestive resilience depending on diet direction
- •Monitor fecal pH and clinical signs for at least 96 hours after any abrupt diet change, as peak microbiome alterations occur at this timepoint
Key Findings
- •Changing from hay-only to complete extruded diet reduced alpha diversity at 24 hours with decreased Firmicutes and increased Bacteroidetes
- •Fecal pH decreased and Verrucomicrobia increased 96 hours after diet change from hay to extruded diet
- •Community structure differed significantly 96 hours post-diet change but not at 24 hours for hay-to-extruded transitions
- •Diet composition influences the magnitude and timing of microbiome response to sudden dietary changes in horses