Exogenous lactobacilli mitigate microbial changes associated with grain fermentation (corn, oats, and wheat) by equine fecal microflora ex vivo.
Authors: Harlow Brittany E, Lawrence Laurie M, Harris Patricia A, Aiken Glen E, Flythe Michael D
Journal: PloS one
Summary
# Editorial Summary When horses consume grain-based feeds that exceed their foregut digestive capacity, undigested starch reaches the hindgut where it undergoes rapid bacterial fermentation, potentially disrupting microbial balance and precipitating metabolic disturbances. Harlow and colleagues investigated whether supplemental lactobacilli could modulate this process using an ex vivo model, incubating faecal material from three geldings with ground corn, wheat, or oats (1.6% w/v starch) alongside one of three Lactobacillus species or a combination, measuring pH, amylolytic bacteria, lactate-utilising bacteria, and Group D Gram-positive cocci after 24 hours. Across all three grain types, exogenous lactobacilli—particularly *L. reuteri* and *L. acidophilus*—successfully inhibited pH decline (P < 0.0001), reduced populations of starch-fermenting bacteria, and increased lactate-utilising bacteria, effects that were most pronounced during corn and wheat fermentations. Remarkably, even autoclaved (dead) lactobacilli produced similar effects, suggesting the mechanism involves more than direct competition for resources, possibly including production of antimicrobial metabolites or modulation of bacterial adhesion. For practitioners managing horses on grain-supplemented diets, particularly those at risk of hindgut acidosis, these findings suggest potential benefit from targeted lactobacillus supplementation, though further in vivo research is warranted to establish clinical efficacy and optimal dosing protocols.
Read the full abstract on PubMed
Practical Takeaways
- •Probiotic supplementation with L. reuteri or L. acidophilus may help stabilize hindgut pH when high-grain diets are fed, particularly with corn or wheat-based concentrates
- •The mechanism appears to involve bacterial metabolites rather than live-cell competition, suggesting formulation flexibility for commercial probiotic products
- •While ex vivo results are promising, in vivo efficacy in live horses consuming grain must be confirmed before changing feeding protocols
Key Findings
- •Exogenous lactobacilli (L. reuteri and L. acidophilus) inhibited pH decline in corn and wheat fermentations, with greatest effects on highest-acidification substrates (P < 0.0001)
- •Lactobacilli additions decreased amylolytic bacteria populations while increasing lactate-utilizing bacteria across corn and wheat fermentations (P < 0.0001)
- •L. reuteri was most effective, producing lowest Group D Gram-positive cocci counts and highest lactobacilli and lactate-utilizer populations regardless of bacterial viability (P < 0.05)
- •Dead (autoclaved) lactobacilli produced similar fermentation effects as live cells, indicating mechanism involves metabolite signaling rather than simple nutrient competition