Age-Related Differences in Short-Term Transportation Stress Responses of Horses

Transportation of horses on short journeys can lead to an increase in stress. There are known ageassociated changes in immune and metabolic responses in horses; however, no research exists evaluating how age may influence these responses to transportation stress. Eleven mares within two age groups, aged (n = 5, 22 & PLUSMN; 1 year) or young (n = 6, 2 & PLUSMN; 1 year), were transported 1 hour and 20 minutes. Peripheral blood and saliva were collected before and after transportation at baseline (2 to 3 weeks prior to transportation), 24 hours pre-transport, 1 hour before loading, 15 minutes, 30 minutes, 1 to 3 hours, 24 hours and 8 days post-transport. Heart rates, rectal temperatures, under the tail temperatures, serum cortisol, plasma ACTH, serum insulin, salivary cortisol and salivary IL-6 were measured. Whole blood gene expression of the cytokines IL-1b, IL-2, IL-6, IL-10, IFN & gamma; , and TNF & alpha; were determined through qPCR, and peripheral blood mononuclear cells were isolated, stimulated, and stained to determine IFN & gamma; and TNF & alpha; production. Serum cortisol ( P < .0 0 01), salivary cortisol ( P < .0 0 01) and heart rate ( P = .0 0 02) increased in response to transportation with no age differences. Rectal ( P = .03) and under the tail temperatures ( P = .02) were increased in young versus aged horses. ACTH was higher in aged horses ( P = .007) and post-transportation ( P = .0 0 01). Aged horses showed a greater increase in insulin compared with young horses ( P < .0 0 01). While age does not seem to impact cortisol responses to short-term transportation in horses, it did influence the post transportation insulin response to stress in aged horses. Published by Elsevier Inc.