Providing Horse Transport Breaks

Horses are shipped long distances for various reasons, including breeding, competitions, and sales ... but at what toll?

According to lead author Carolyn Stull, MS, PhD, Dipl. ACVN (nutrition), from the School of Veterinary Medicine at the University of California, Davis, "previous studies have reported that long-term road transport increases the stress parameters of cortisol, total white blood cell counts, and alters various ratios of white blood cell subpopulations."

Stull explained that these changes are indicative of stress and have been implicated as causing stress-related immune suppression.

"Since transport is known to be stressful and few studies have examined the effect of a mid-journey rest, the purpose of this study was to examine if a 12-hour rest and feeding stop during a long journey would impact the horses' immune response," explained Stull.


A mid-journey rest and feeding might interrupt the decline in cell numbers associated with immune responses.

In this study, 38 horses of various breeds were randomly divided into one of two groups: the continuous 24 hour transport group or the rest group which was subjected to two 12 hour transport sessions separated by a 12 hour offloaded rest period.

Overall results showed no significant differences in various "stress" parameters including cortisol concentrations, total white blood cell counts, counts of individual types of white blood cells (neutrophils and lymphocytes), or the specific subpopulations of lymphocytes including CD8a+ and CD21+.

"What we did find is that the CD3+, CD4+, and CD8b+ subpopulations of T lymphocytes did recover toward normal resting levels in the group of horses that were permitted a 12 hour rest," said Stull. "These results suggest that horses undergoing a long journey (24 hours in this study) experience a cortisol-mediated response to stress that result in a redistribution of certain white blood cell types."

Together this data supports the hypothesis that a mid-journey rest and feeding will interrupt the decline in cell numbers associated with immune responses and allow these populations to recover towards normal, resting levels in long-term traveling equids.

The study, "Immunophysiological responses of horses to a 12-hour rest during 24 hours of road transport," was published in the May 10, 2008, edition of The Veterinary Record.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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