Effects of Starch Overload and Cecal Buffering on Fecal Microbiota of Horses.
Authors: Bustamante Caio C, de Paula Vanessa B, Rabelo Isabela P, Fernandes Camila C, Kishi Luciano T, Canola Paulo A, Lemos Eliana Gertrudes de M, Valadão Carlos Augusto A
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Corn starch overload is known to disrupt the equine hindgut microbiota and precipitate metabolic disorders, yet interventions to mitigate these effects remain poorly defined. Bustamante and colleagues investigated whether intracecal infusion of an alkaline buffer solution (magnesium and aluminium hydroxide) could stabilise the microbiota and clinical signs in ten horses experimentally overloaded with corn starch, monitoring faecal composition and microbial communities over 72 hours using molecular analysis. Starch overload significantly reduced microbial richness and diversity overall (p < 0.001 and p = 0.001 respectively); however, buffered horses paradoxically showed exaggerated shifts toward amylolytic dominance (Bifidobacterium increased from 0.0% to 5.6%; Lactobacillus from 0.1% to 7.4%) paired with suppression of protective fibrolytic taxa (Lachnospiraceae and Ruminococcaceae each declining by ~50%, p < 0.05), whereas saline-treated controls showed more modest changes. Critically, buffered animals exhibited greater abdominal discomfort and lameness that correlated strongly with dysbiotic bacterial ratios (r > 0.5 for amylolytic bacteria; r < 0.1 for fibrolytic bacteria), indicating that alkali infusion not only failed to provide prophylaxis but actively intensified intestinal disturbance and laminitis risk. These findings suggest that pH manipulation alone is an ineffective—and potentially counterproductive—strategy for managing starch-induced dysbiosis, and practitioners should focus on preventing overload events and supporting fibre-digesting microbial populations rather than attempting to buffer the consequences after the fact.
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Practical Takeaways
- •Intracecal buffer injection does not mitigate starch overload effects and may worsen clinical outcomes including lameness and abdominal pain—avoid this intervention
- •Starch overload causes dysbiosis with reduced microbial richness and diversity; management should focus on prevention of starch overload rather than attempted treatment with buffers
- •Watch for increased laminitis risk following starch overload events; the dysbiotic shift toward amylolytic dominance correlates with lameness signs
Key Findings
- •Corn starch overload reduced fecal microbiota richness (p < 0.001) and diversity (p = 0.001) in horses
- •Starch-buffer treatment increased amylolytic bacteria (Bifidobacterium 0.0-5.6%, Lactobacillus 0.1-7.4%) more than starch-saline treatment
- •Starch-buffer treatment decreased fibrolytic bacteria (Lachnospiraceae 10.2-5.0%, Ruminococcaceae 11.7-4.2%) compared to starch-saline
- •Cecal buffer infusion intensified intestinal disturbances and increased laminitis risk rather than preventing them, with greater signs of abdominal discomfort and lameness