Serum immunoglobulin concentrations in horses racing a multiday endurance event

Abstract

Chronic exercise can alter immune function. The objective of this study was to determine the effect of training and racing on serum immunoglobulin fractions (sIg) in horses participating in a multiday endurance event. Blood was obtained from 54 horses the day before a multiday race event with distance categories of 40 km (n=10) or 80 km (n=44) per day; from all available horses after completing each day; and once from 15 sedentary control horses. sIgGa, IgGb, sIgG(T), sIgA, and sIgM concentrations were measured via equine-specific ELISA, and data were analysed via repeated measures ANOVA (P<0.05, mean ± standard error). Ten horses completed 40 km once, and 44, 18 and 9 horses completed one, two and three 80 km days, respectively. Distance category and number of days raced had no effect on any immunoglobulin subtype. For horses in the 80 km category, sIgA before racing (1.97±0.14 mg/dl) was similar to controls (1.48±0.19) and after one, two or three days of racing (1.98±0.13, 1.80±0.15 and 1.76±0.26, respectively). Similarly, sIgM before racing (1.02±0.05 mg/dl) was not different to controls (1.08±0.12) and after one, two or three days of racing (1.03±0.06, 0.91±0.08 and 0.89±0.11). Similar findings were observed for sIgG(T) and sIgGa. For horses in the 40 km category, immunoglobulin subtype concentrations did not differ from before to after one day of racing, or from control horses, with the exception that sIgGb before racing (7.00±0.57), similarly to horses racing 80 km days (7.65±0.41), was significantly higher than in sedentary horses (5.71±0.54 mg/dl). This study identified higher sIgGb concentrations in trained endurance horses compared to sedentary horses, perhaps reflecting immune stimulation from disease exposure or more frequent vaccination.