Travel causes a stress response in horses, according to multiple research studies. But do senior horses experience a different level of stress than younger horses?

Researchers attempted to answer that question in one study published in late 2023, which focused on short-duration transportation stress in senior horses.1

About the Research

Age-associated changes in components of immune function and markers of inflammation occur in older horses following transport, according to previous research.

This study compared 11 mares in two age groups: aged (five mares, 21-23 years old) and young (six mares, 1-3 years old). Researchers transported the horses for 1 hour and 20 minutes. 

Blood and saliva collected 2-3 weeks before transport established a baseline. Researchers took additional samples at 24 hours pre-transport and 1 hour before loading. They took samples 15 minutes, 30 minutes, 1-3 hours, 24 hours, and 8 days post-transport. 

Serum cortisol, plasma ACTH, serum insulin, salivary cortisol, and salivary IL-6 were analyzed from blood samples. Whole blood gene expression of the cytokines IL-1b, IL-2, IL-6, IL-10, IFNγ, and TNFα were determined through qPCR, and peripheral blood mononuclear cells were isolated, stimulated, and stained to determine IFNγ and TNFα production. 

Other sampling that could indicate stress included heart rate, rectal temperature, and temperature under the tail.

Research Results

Serum cortisol, salivary cortisol, and heart rate increased in response to transportation; this did not differ between the age categories.

Aged horses had decreased rectal and under-the-tail temperatures compared to young horses, but these measurements stayed within normal limits.

ACTH was higher in aged horses. It increased 15 minutes post-transportation in two-fifths of the aged horses.

Aged horses showed a greater increase in insulin compared with young horses following short-duration transport. While age does not seem to impact cortisol responses in short-term transportation in horses, it did influence the post-transportation insulin response to stress in aged horses.

Final Words

“Short-term transportation causes acute stress in horses regardless of age,” noted the researchers.

They said that the research proved that aged horses have different endocrine and immune responses post-transportation.

“In particular, the increase in serum insulin and plasma ACTH in aged horses post-transportation should be considered,” the research stated.

Owners should keep this in mind when transporting horses with metabolic disorders, or when trailering a senior horse to a veterinary clinic for endocrine disorder diagnostic testing.

They recommended that future research be conducted using horses with indulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID, formerly called Cushing’s disease). 

Reference

Age-Related Differences in Short-Term Transportation Stress Responses of Horses. Erica T. Jacquay, Patricia A. Harris, Amanda A. Adams. Journal of Equine Veterinary Science. 2023.

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  • Kimberly S. Brown and Jewell

    Kimberly S. Brown is an award-winning writer and publisher. She founded My Senior Horse for Equine Network and Linda Mars in her retirement, and now she is an editor of the brand. Brown previously had spent 10 years at Equine Network. Prior to that she worked for three years in equine nutrition after she retired from nearly 30 years working at The Blood-Horse. Brown spent the last 15 years of her time at that organization creating and developing the award-winning The Horse and TheHorse.com.

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