Effect of age and the individual on the gastrointestinal bacteriome of ponies fed a high-starch diet.
Authors: Morrison Philippa K, Newbold Charles J, Jones Eleanor, Worgan Hilary J, Grove-White Dai H, Dugdale Alexandra H, Barfoot Clare, Harris Patricia A, Argo Caroline McG
Journal: PloS one
Summary
# Editorial Summary: Gastrointestinal Bacterial Response to High-Starch Feeding in Ponies Morrison and colleagues tracked changes in faecal bacterial communities across 23 Welsh Section A pony mares (aged 5–15 years and ≥19 years) as they transitioned from maintenance hay feeding to a high-starch diet incorporating 2g micronized steam-flaked barley per kg body mass over a 5-week period. Using 16S rRNA sequencing, the researchers identified consistent shifts in bacterial phyla—notably increased Candidatus Saccharibacteria and Firmicutes with reduced Fibrobacteres—though age had minimal influence on these compositional changes. At the genus level, Streptococcus abundance increased during high-starch feeding, but critically, this response varied substantially between individual animals; in ponies classified as Streptococcus 'responders', bacterial diversity actually declined during the dietary transition, whilst faecal pH and volatile fatty acid concentrations showed considerable inter-individual variation. These findings underscore that whilst high-starch feeding triggers predictable microbial shifts in pony hindguts, the magnitude and functional consequences differ markedly between individuals, suggesting that standardised feeding recommendations may not account for individual susceptibility to dysbiosis-related complications such as colic or laminitis. Practitioners should recognise that monitoring faecal indicators and clinical signs during dietary transitions may be more informative than assuming uniform bacterial responses across a group.
Read the full abstract on PubMed
Practical Takeaways
- •Older ponies (≥19 years) show similar gastrointestinal adaptation to high-starch diets as younger animals, so age alone should not restrict dietary management decisions
- •Individual ponies respond very differently to the same high-starch feed in terms of bacterial composition and fermentation patterns—monitor individual animals rather than assuming group-wide responses
- •High-starch dietary transitions shift the hindgut microbiota toward starch-fermenting bacteria; consider gradual introductions and monitor for signs of digestive upset, particularly in ponies with large Streptococcus responses
Key Findings
- •Age had minimal effect on faecal bacteriome response to high-starch diet transition in ponies aged 5-15 years versus ≥19 years
- •Dietary transition from hay to high-starch barley increased Candidatus Saccharibacteria and Firmicutes phyla while reducing Fibrobacteres abundance
- •Streptococcus abundance increased during high-starch feeding but responses were inconsistent across individual animals, with bacterial diversity reduced in 'responders'
- •Considerable inter-individual variation in faecal pH, volatile fatty acid concentrations, and bacterial population responses to the same diet suggests functionally different hindgut bacterial populations among ponies