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

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 IFN[gamma], IL-1[beta], IL-2, IL-4, IL-6, IL-8, IL-10, IL-12[alpha], IL-17[alpha], SAA1, and TNF[alpha] in whole blood were measured. Peripheral blood mononuclear cells were isolated, stimulated with PMA/ionomycin, and stained for IFN[gamma] and TNF[alpha] 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-12[alpha], IL-17[alpha], change ([DELTA]) in the % and mean fluorescence intensity (MFI) of IFN[gamma].sup.+ lymphocytes after stimulation, or [DELTA] in the % and MFI of TNF[alpha].sup.+ lymphocytes after stimulation. Supplementation decreased IL-1[beta] and SAA1 expression. Transport increased total cortisol concentration, body temperature, and IL-2, IL-6, and IL-10 expression but decreased IL-1[beta], TNF[alpha], and IFN[gamma] 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.