Faecal microbiota of forage-fed horses in New Zealand and the population dynamics of microbial communities following dietary change.
Authors: Fernandes Karlette A, Kittelmann Sandra, Rogers Christopher W, Gee Erica K, Bolwell Charlotte F, Bermingham Emma N, Thomas David G
Journal: PloS one
Summary
# Editorial Summary Dietary transitions in horses trigger rapid restructuring of faecal bacterial communities, but the magnitude and timeframe of these changes remained poorly characterised until Fernandes and colleagues examined yearling Thoroughbreds abruptly switched from ensiled forage-grain diets to pasture. Using 16S and 18S rRNA gene pyrosequencing, researchers tracked microbial populations over three weeks in horses previously maintained on either conserved forage or pasture, collecting samples at four-day intervals to capture community dynamics. Bacterial composition shifted markedly within four days of dietary change, with significant differences in four key genera (BF311, CF231, unclassified Clostridiales and Lachnospiraceae members) resolving as the diet-switched group converged towards the pasture-fed baseline, whilst archaeal and protozoan populations remained remarkably stable throughout. These findings underscore that whilst abrupt transitions provoke substantial bacterial restructuring, this adaptation occurs faster than previously expected—a reassuring observation for practitioners managing emergency dietary changes, yet a reminder that the four-day stabilisation period may still entail increased risk of digestive upset as populations rebalance, warranting closer monitoring and potentially graduated transitions where possible.
Read the full abstract on PubMed
Practical Takeaways
- •Abrupt dietary transitions cause rapid bacterial shifts in the hindgut within days rather than weeks; bacterial adaptation is faster than often assumed in field practice
- •While bacterial populations adjust quickly, the overall microbial ecosystem remains stable enough that horses tolerate abrupt pasture transitions better than traditional gradual transition protocols might suggest
- •Individual dietary history (grain-based vs pasture-based) creates distinct microbial profiles, but these differences are temporary and reversed quickly with dietary change
Key Findings
- •Faecal bacterial communities showed significant differences between pasture-fed and forage-grain-fed horses at baseline (P < 0.017), primarily in genera BF311, CF231, Clostridiales, and Lachnospiraceae
- •Bacterial community composition of grain-fed horses converged to pasture-fed horses within 4 days of abrupt dietary transition to pasture
- •Archaeal and ciliate protozoal communities remained stable despite dietary change, indicating selective responsiveness of different microbial groups
- •High bacterial diversity (Simpson's index > 0.8) was maintained in both dietary groups throughout the study period