The oral glucose test predicts laminitis risk in ponies fed a diet high in nonstructural carbohydrates.
Authors: Meier, de Laat, Reiche, Pollitt, Walsh, McGree, Sillence
Journal: Domestic animal endocrinology
Summary
# Editorial Summary: Oral Glucose Testing as a Laminitis Predictor in Ponies Researchers investigated whether insulin and glucose responses to oral carbohydrate challenges could identify ponies at risk of developing laminitis. Thirty-seven ponies underwent an oral glucose test (1 g dextrose/kg bodyweight) followed by an 18-day dietary challenge of 12 g nonstructural carbohydrates per kilogramme per day; blood samples were analysed for insulin and glucose responses, and clinical laminitis was assessed blindly and confirmed radiographically. Of the cohort, 38% (14 ponies) developed Obel grade 1 or 2 laminitis, with affected animals showing significantly higher maximum glucose concentrations (14.9 versus 10.7 mM; P = 0.04) and serum insulin levels (396 versus 216 μIU/mL; P = 0.02) in response to the high-carbohydrate diet. Critically, laminitis incidence increased sharply with post-glucose insulin thresholds: zero cases occurred when insulin remained below 50 μIU/mL, rising to 35% incidence at 50–195 μIU/mL and 86% when exceeding 195 μIU/mL—a finding that provides quantifiable risk stratification for practitioners. Ponies with concurrent pituitary pars intermedia dysfunction showed particularly high laminitis rates (50% of those with elevated basal ACTH, 100% of those with clinical PPID signs), suggesting that metabolic and endocrine dysfunction interact to amplify laminitis susceptibility. For equine practitioners, these results support using oral glucose testing as a practical, cost-effective screening tool to identify high-
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Practical Takeaways
- •The oral glucose test with insulin measurement effectively identifies high-risk ponies: insulin >195 μIU/mL post-dextrose indicates 86% laminitis risk on high-NSC diets
- •Restrict nonstructural carbohydrate intake (below 12 g/kg BW/d) in ponies showing hyperinsulinemic responses, especially those with elevated ACTH or clinical PPID signs
- •Combine OGT results with basal ACTH assessment and clinical evaluation—ponies with both PPID clinical signs and hyperinsulinemia warrant aggressive dietary management to prevent laminitis
Key Findings
- •Ponies with post-dextrose insulin >195 μIU/mL had 86% laminitis incidence vs 0% when <50 μIU/mL during oral glucose test
- •Diet challenge high in nonstructural carbohydrates (12 g NSC/kg BW/d) induced Obel grade 1-2 laminitis in 38% of ponies (14/37)
- •Laminitis cases showed significantly higher maximum glucose (14.9 vs 10.7 mM, P=0.04) and insulin responses (396 vs 216 μIU/mL, P=0.02) to dietary challenge
- •All 5 ponies with clinical PPID signs developed laminitis (100%), versus 27% in elevated ACTH cases without clinical PPID signs (P=0.009)