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Effects of racing on lymphocyte proliferation in horses
Live L Nesse1, Grete Irene Johansen, Anne K Blom
1Department of Bacteriology, National Veterinary Institute, Oslo, Norway.
Objective:
To measure the lymphocyte proliferation response in horses 12 to 16 hours after completion of a race.
Animals:
8 Thoroughbreds that competed in 14 races and 3 control Thoroughbreds that did not race.
Procedure:
Horses participated in races during the late afternoon or evening. Venous blood samples were collected on a morning before a race (1 or 2 days before the race or on the day of the race), on the afternoon of a race (40 to 60 minutes after the race), and on the morning of the day after a race (12 to 16 hours after the race). Lymphocyte proliferation responses and WBC count were measured in samples obtained in the mornings. Plasma cortisol was measured in all samples.
Results:
Lymphocyte proliferation responses were significantly reduced and WBC counts significantly increased 12 to 16 hours after a race. Plasma cortisol concentrations were significantly increased 40 to 60 minutes after a race. In samples from the control horses, lymphocyte proliferation responses, WBC counts, or plasma cortisol concentrations did not differ significantly among time periods.
Conclusions And Clinical Relevance:
A decrease in proliferative responses of circulating lymphocytes can be found as late as 12 to 16 hours after a horse participates in a race. Although the clinical consequences of these exercise-related alterations of the immune response are not yet known, managers of horses should take into account that the immune system of a horse may be affected by racing.