Short-term transport stress and supplementation alter immune function in aged horses

Abstract

Long-distance transport is associated with stress-related changes in equine immune function, and shipping-associated illnesses are often reported. Horses are frequently transported short distances, yet the effects of short-term transport on immune function remain largely unknown. Twelve horses, aged 15–30 yr, were assigned to either the control (n = 6) or treatment (n = 6) groups; treatment horses received a daily antioxidant supplement 3 weeks before and after transport. All horses were transported for approximately 1.5–2 hr on Day 0. Blood was collected via jugular venipuncture at 15-min pre- and post-transport and on Days –21, 1, 3, 7, 14, and 21. Body temperature, heart rate, body weight, total cortisol, and gene expression of IFNγ, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12α, IL-17α, SAA1, and TNFα in whole blood were measured. Peripheral blood mononuclear cells were isolated, stimulated with PMA/ionomycin, and stained for IFNγ and TNFα before analysis via flow cytometry. Statistical analyses were performed with significance set at P < 0.05 (SAS 9.4). Transport and supplementation did not appear to affect body weight, heart rate, IL-4, IL-8, IL-12α, IL-17α, change (Δ) in the % and mean fluorescence intensity (MFI) of IFNγ+ lymphocytes after stimulation, or Δ in the % and MFI of TNFα+ lymphocytes after stimulation. Supplementation decreased IL-1β and SAA1 expression. Transport increased total cortisol concentration, body temperature, and IL-2, IL-6, and IL-10 expression but decreased IL-1β, TNFα, and IFNγ expression. Short-term transportation affected physiological, endocrine, and immune responses; supplementation may ameliorate inflammation in aged horses. Immune responses were most altered at 15-min post-transport and typically recovered by Day 1, suggesting that horses may be vulnerable to disease during and almost immediately after short-term transport.

Welfare of equidae during transport

“…Many studies, as exemplified in previous sections, have explored the influence of transport on the immune response and physiological parameters of transported horses, demonstrating an important role even in journeys as short as 1.5–2 h (Miller et al., 2021), and potentially in the development of transport pleuropneumonia, often called ‘shipping fever’. Raidal et al.…”

“Not All Who Wander Are Lost”: The Life Transitions and Associated Welfare of Pack Mules Walking the Trails in the Mountainous Gorkha Region, Nepal

“…To mitigate against these issues vehicle design needs to incorporate adequate ventilation and thermal insulation, be thoroughly cleaned and disinfected between uses, transportation of equids from different locations limited during the same journey and equids travelled in low densities, preferably during cooler conditions [ 46 ]. Stress from transportation causes the activation of hormones which in turn, raise heart and respiratory rates, sweating and defecation increasing the already hot and contaminated vehicle whilst also influencing the equid’s immune response leaving them more susceptible to disease [ 37 , 46 , 52 ].…”

Equine Influenza Virus: An Old Known Enemy in the Americas

“…In addition to physical contact between animals, travel conditions, mixing with other vaccinated and unvaccinated horses, and poor biosecurity could contribute to an increased risk of infection. Long- and short-term transportation affects physiological, endocrine, and immune responses as soon as 15 min post-transport, implying that horses may be vulnerable to disease during and almost immediately after short-term transport [ 90 ]. In mathematical modeling, mixing vaccinated and unvaccinated animals and the use of isolation could not only reduce disease burden in equine populations but also reduce disease transmission and decrease the cumulative incidence of EIV [ 91 , 92 ].…”