Effect of varying the dose of corn syrup on the insulin and glucose response to the oral sugar test.
Authors: Jocelyn N A, Harris P A, Menzies-Gow N J
Journal: Equine veterinary journal
Summary
# Editorial Summary Whilst the oral sugar test has become established as a screening tool for equine insulin dysregulation, previous validation work examined only the lowest dose of corn syrup (0.15 mL/kg bodyweight). Jocelyn and colleagues conducted a randomised crossover study in eight ponies—five with a history of laminitis and three without—administering three different doses of corn syrup (0.15, 0.3 and 0.45 mL/kg) with seven-day washout periods between tests, measuring serum insulin and glucose responses over two hours using validated laboratory methods. The 0.15 and 0.3 mL/kg doses produced comparable insulin responses, but the higher 0.45 mL/kg dose elicited significantly greater insulin elevation at most timepoints; critically, only the highest dose reliably distinguished between laminitis-prone and non-laminitis-prone ponies (mean serum insulin 146 versus 86 μiu/mL at 60 minutes, P<0.01). Using the area-under-the-curve calculation for insulin improved the test's repeatability from 0.51 to 0.83, and results remained consistent whether ponies were fasted or had continued pasture access. For practitioners, these findings suggest increasing the corn syrup dose to 0.45 mL/kg and calculating insulin AUC rather than relying on single timepoint measurements may improve the diagnostic utility of the oral sugar test for identifying insulin dysregulation—though the authors acknowledge their small sample size and limited testing occasions warrant cautious interpretation.
Read the full abstract on PubMed
Practical Takeaways
- •If using the oral sugar test to screen for insulin dysregulation in ponies, consider adopting the 0.45 mL/kg bwt corn syrup dose rather than the standard 0.15 mL/kg, as it better identifies insulin-dysregulated animals at risk of laminitis.
- •Using area under the curve (AUC) rather than single time-point insulin values improves test reliability and repeatability.
- •The test does not require strict fasting protocols—ponies can be tested while on pasture, making clinical application more practical.
Key Findings
- •A 0.45 mL/kg bwt corn syrup dose produced significantly different serum insulin responses compared to 0.15 and 0.3 mL/kg bwt doses at most time points (P<0.01).
- •Only the 0.45 mL/kg bwt dose significantly differentiated insulin concentrations between laminitis-affected ponies (146 μiu/mL) and non-laminitic ponies (86 μiu/mL) at 60 minutes (P<0.01).
- •Repeatability of serum insulin at 60 min with 0.45 mL/kg bwt improved from 0.51 to 0.83 when using area under the curve (AUC) analysis.
- •Fasted and pasture-access conditions produced no significant difference in results, suggesting the test can be performed without strict pre-test management.