Immunological response to long-term transport stress in mature horses and effects of adaptogenic dietary supplementation as an immunomodulator.
Authors: Stull C L, Spier S J, Aldridge B M, Blanchard M, Stott J L
Journal: Equine veterinary journal
Summary
# Editorial Summary Prolonged horse transport triggers a significant immunosuppressive response characterised by elevated cortisol and neutrophilia alongside suppression of key lymphocyte populations (CD3+, CD4+, CD8+ and CD21+ subsets), though these parameters normalise within 24 hours of unloading. Researchers administered either an adaptogenic supplement or placebo to 19 mature horses over 28 days of stabling, then transported six horses from each group for 24 hours whilst monitoring blood immunophenotype and functional markers at baseline, during transport and recovery. Whilst the supplement demonstrated modest immunomodulatory effects on CD21+ and CD8+ lymphocyte populations in stabled horses, these benefits did not translate to protection during the transport challenge itself, suggesting adaptogenic supplementation may have limited capacity to buffer the acute physiological stress response. The findings reveal a critical post-transport window of immunological vulnerability lasting approximately 24 hours—a period during which transported horses face heightened susceptibility to infectious disease—making rigorous biosecurity protocols and careful observation essential following long journeys. For practitioners managing horses in high-risk scenarios (competition, sales, long-distance haulage), these results underscore the importance of minimising transport duration where possible and implementing prophylactic management strategies that extend beyond dietary supplementation alone.
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Practical Takeaways
- •Long-distance transport creates a 24-hour window of immunological vulnerability when horses are at increased risk of infectious disease; implement biosecurity protocols during and immediately after transport
- •Transported horses show predictable stress hormone and immune cell changes that resolve quickly, but individual susceptibility varies; monitor high-risk horses closely post-transport
- •Adaptogenic supplements may have minor immunomodulatory benefits in stabled conditions but do not appear to protect against transport-induced immunosuppression
Key Findings
- •24-hour transport caused significant elevations in cortisol, neutrophil count, and white blood cell counts (P<0.05)
- •Lymphocyte subpopulations (CD3+, CD4+, CD8+, CD21+) decreased significantly during transport (P<0.05)
- •Normal lymphocyte phenotypic profiles returned within 24 hours of recovery
- •Adaptogenic supplement showed immunomodulatory effects on CD21+ and CD8+ in stabled horses but not in transported horses