The impact of short-term transportation stress on insulin and oral sugar responses in insulin dysregulated and non-insulin dysregulated horses.
Authors: Jacquay Erica T, Harris Patricia A, Adams Amanda A
Journal: Equine veterinary journal
Summary
# Editorial Summary Transportation is a routine management practice for many horses, yet its effects on metabolic testing remain poorly characterised, particularly for insulin dysregulated (ID) individuals. Jacquay and colleagues investigated whether a standard 1.5-hour trailer journey altered insulin responses to an oral sugar test (OST) differently in ID versus non-ID mares, recruiting seven horses in each group and collecting blood samples at multiple timepoints before transport, immediately post-unloading, and up to 24 hours afterwards, with OST performed both 24 hours before and 3 hours after the journey. As expected, ID horses demonstrated substantially elevated baseline insulin (109.9 μU/mL versus 30.2 μU/mL in non-ID animals), yet the critical finding was the exaggerated post-OST insulin response observed following transport: ID horses showed insulin levels reaching 284.6 μU/mL at 60 minutes after the sugar challenge post-transport, compared with 154.6 μU/mL pre-transport. More concerning, non-ID horses tested 3 hours post-transportation produced a mean OST insulin of 56.6 μU/mL—exceeding the diagnostic threshold of 45 μU/mL that would typically indicate ID status. These results carry significant implications for practitioners: conducting diagnostic OSTs within a few hours of transport may yield false-positive results and misidentify metabolically normal horses as dysregulated. Clinicians should either postpone metabolic testing until 24 hours or more after transport, or acknowledge this timing limitation when interpreting results and counselling owners on dietary management and exercise restriction for recently transported horses.
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Practical Takeaways
- •Do not perform oral sugar tests within 3 hours of transportation for ID diagnosis, as stress-induced insulin elevation may yield false positive results in non-dysregulated horses
- •Allow minimum 24 hours recovery post-transport before conducting endocrine testing for accurate ID status assessment
- •Be aware that transportation stress significantly amplifies insulin response to oral sugar challenge, particularly in horses with pre-existing insulin dysregulation
Key Findings
- •Mean serum insulin was significantly higher in ID horses (109.9 μU/mL) compared to non-ID horses (30.2 μU/mL, p<0.001)
- •ID horses showed increased insulin response to oral sugar test post-transportation (284.6 μU/mL at T60) compared to pre-transportation (154.6 μU/mL)
- •Non-ID horses demonstrated mean OST insulin of 56.6 μU/mL post-transportation, exceeding the 45 μU/mL diagnostic threshold for ID
- •Performing oral sugar testing 3 hours post-transportation may result in inaccurate insulin dysregulation diagnosis due to stress-induced changes