Immunophysiological responses of horses to a 12-hour rest during 24 hours of road transport.
Authors: Stull C L, Morrow J, Aldridge B A, Stott J L, McGlone J J
Journal: The Veterinary record
Summary
# Editorial Summary: Rest Periods During Long-Distance Transport Preserve Immune Function in Horses Road transport triggers a significant physiological stress response in horses, characterised by elevated cortisol and a shift towards neutrophilia with relative lymphopenia—changes that could compromise immune competence during and after journey. Researchers compared 38 horses undergoing either 24 hours of continuous transport or two 12-hour transport periods separated by 12 hours of off-loading, rest and feeding, collecting blood samples before loading, immediately after transport and following 24 hours' recovery. Whilst both groups showed transport-induced increases in cortisol and neutrophil counts with decreased lymphocyte populations, the critical finding was that a single 12-hour rest-stop significantly attenuated the decline in specific lymphocyte subpopulations (CD3+, CD4+ and CD8b+ cells), allowing these immune cells to recover towards baseline levels rather than reaching the nadir seen in continuously transported horses. For practitioners managing long-distance transport, particularly during competition seasons or breeding stock movements, this evidence supports the strategic use of rest periods to preserve immune function and potentially reduce the risk of transport-related illness during the vulnerable post-journey period.
Read the full abstract on PubMed
Practical Takeaways
- •Including a 12-hour rest-stop during 24-hour road transport helps preserve immune function by allowing lymphocyte subpopulations to recover, particularly CD3+, CD4+, and CD8b+ cells
- •Transport stress significantly elevates cortisol and alters immune cell populations; rest intervals provide measurable physiological benefit even if some markers (total leucocytes, overall neutrophil counts) show similar responses between split and continuous transport
- •For long-distance transport operations, implementing mandatory rest periods with off-loading, feeding, and recovery time is supported as a welfare and health optimization strategy
Key Findings
- •Continuous 24-hour transport significantly increased cortisol concentrations, neutrophil counts, and neutrophil:lymphocyte ratios while decreasing all lymphocyte subpopulation cell types
- •A 12-hour rest-stop during 24 hours of transport interrupted transport-related decline in CD3+, CD4+, and CD8b+ lymphocyte subpopulations, allowing recovery toward resting levels
- •No significant differences between continuous transport and split transport (12/12) groups for cortisol, total leucocyte counts, and neutrophil:lymphocyte ratios overall
- •Rest-stop intervention during transport promoted partial immunological recovery in specific lymphocyte subpopulations