An in vitro model of the horse gut microbiome enables identification of lactate-utilizing bacteria that differentially respond to starch induction.
Authors: Biddle Amy S, Black Samuel J, Blanchard Jeffrey L
Journal: PloS one
Summary
# Editorial Summary The development of laminitis following sudden starch intake involves a well-documented cascade: undigested starch reaches the hindgut, stimulates lactic acid-producing bacteria, and causes lactate and acid accumulation that compromises gut barrier function and triggers systemic inflammation. Biddle and colleagues used an in vitro fermentation model with fecal inocula from three horses to investigate why lactate-clearing mechanisms fail acutely and why recovery varies between individuals, employing 16S rRNA sequencing to track microbial community shifts and measuring short-chain fatty acid (SCFA) production, pH, and gases over 12-hour periods following starch and/or lactate supplementation. Their findings revealed distinct microbial profiles associated with successful lactate clearance: communities that recovered lactate levels showed corresponding increases in propionate and acetate, with Megasphaera elsdenii reaching >70% relative abundance, whilst Veillonella montpellierensis dominated in cultures where lactate fell more gradually. This work suggests that individual horses possess different baseline microbial compositions and lactate-utilising capacities, potentially explaining variable susceptibility to starch-induced acidosis and laminitis. For practitioners, these results imply that strategies targeting enrichment of specific lactate-utilising taxa—through dietary management, prebiotics, or targeted probiotics—could theoretically mitigate acidosis risk, though translating in vitro findings to effective in vivo interventions remains a significant challenge requiring further investigation.
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Practical Takeaways
- •Promoting growth of Megasphaera elsdenii and Veillonella montpellierensis through management strategies may help prevent hindgut acidosis during starch challenges.
- •Some horses' microbiomes are inherently better at clearing excess lactate; understanding what enables this resilience could inform probiotic or dietary interventions.
- •This mechanistic understanding of lactate-utilizing bacteria may eventually enable targeted interventions to prevent laminitis in starch-sensitive horses.
Key Findings
- •In vitro fecal microcosms exposed to starch showed pH and short-chain fatty acid patterns similar to in vivo laminitis models.
- •Megasphaera elsdenii reached >70% relative abundance in microcosms that successfully cleared excess lactate following starch induction.
- •Veillonella montpellierensis was enriched in cultures where lactate levels fell, suggesting a secondary lactate-utilizing role.
- •Disparate lactate-clearing abilities between microbial communities suggest specific bacterial profiles confer resistance to starch-induced acidosis.