Resilience of Faecal Microbiota in Stabled Thoroughbred Horses Following Abrupt Dietary Transition between Freshly Cut Pasture and Three Forage-Based Diets.
Authors: Fernandes Karlette A, Rogers Chris W, Gee Erica K, Kittelmann Sandra, Bolwell Charlotte F, Bermingham Emma N, Biggs Patrick J, Thomas David G
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Abrupt dietary changes present a significant management challenge in competition horse systems, particularly when horses rotate between pasture and stabled feeding regimens, yet the microbial consequences of these transitions remain poorly characterised. Researchers tracked faecal microbiota composition in six stabled Thoroughbred mares across six weeks using high-throughput 16S rRNA sequencing, cycling them between fresh pasture and three conserved forage-based diets (chopped ensiled forage alone, ensiled forage with whole oats, and ryegrass hay with whole oats), whilst simultaneously measuring digesta transit time to correlate microbial shifts with dietary passage through the tract. Alpha diversity differed significantly between diets (p < 0.001), with distinct bacterial profiles emerging for each forage type: ensiled forages favoured Firmicutes dominance (62–64%), pasture diets elevated Bacteroidetes (32–38%), and hay promoted Spirochaetes (17%), and critically, faecal microbiota stabilised within 96 hours of transition to ensiled forage-based diets, suggesting faster adaptation than previously anticipated. These findings demonstrate that equine faecal microbiota are more resilient to abrupt dietary transition than the documented risk of gastrointestinal upset might suggest, though the practical implication remains that forage-predominant diets—whether fresh, conserved, or ensiled—support more stable and diverse microbial communities than concentrate-heavy systems, supporting current best-practice recommendations for pasture-based or high-forage management in competition horses.
Read the full abstract on PubMed
Practical Takeaways
- •Horses demonstrate rapid microbiota adaptation to forage-based diet changes within 4 days, supporting the feasibility of rotational feeding systems used in competition horse management
- •Incorporating high proportions of forage (particularly ensiled or hay-based diets) maintains a more stable and resilient faecal microbiota compared to pasture-only systems, potentially reducing GI disturbance risk
- •When unavoidable abrupt dietary transitions occur in stabled competition horses, use of conserved forage-based diets allows for quicker microbiota stabilisation than alternative feeding strategies
Key Findings
- •Faecal microbiota composition was diet-specific with significant differences in alpha diversity (p < 0.001) and beta diversity (ANOSIM, p = 0.001) across diets
- •Stable microbiota profiles were established within 96 hours of transition to ensiled forage-based diets, demonstrating microbial resilience
- •Bacterial phyla differed significantly across diets (p < 0.003), with Firmicutes (62-64%) dominating ensiled forage diets, Bacteroidetes (32-38%) in pasture, and Spirochaetes (17%) in hay diets
- •Changes in faecal bacterial composition corresponded with cumulative intestinal marker transit, linking microbial shifts to digesta passage rates