Alterations in blood viscosity in horses competing in cross country jumping

Packed cell volume and plasma total protein (TP), serum albumin (Alb) and globulin (Glb), and plasma ionized calcium (PCa) concentrations, blood viscosity (BV), and plasma viscosity (PV) were measured in 42 horses at rest and after the cross country jumping phase of a horse trial competition. The BV and PV were determined at 6 shear rates (230, 115, 46, 23, 11.5, 5.75 s-1), using a digital rotational cone and plate microviscometer. A paired t-test was used to determine differences between PCV, TP, Alb, Glb and PCa values at rest and after exercise. The PCV, TP, Alb, and Glb values increased (P < 0.05) in horses after exercise. The PCa concentration decreased (P < 0.05) in horses after exercise. Mean BV and PV in the 42 horses at rest and after exercise were fitted to an asymptotic function. Significant (P < 0.05) correlation at all shear rates was seen between BV at rest and PCV, TP, Alb, Glb, and PCa values at rest; and between BV after exercise and PCV, TP, Alb, Glb, and PCa values after exercise. Significant correlation was not seen between PV at rest and TP, Alb, Glb, and PCa at rest, or between PV after exercise and TP, Alb, Glb, and PCa concentrations after exercise at any shear rate.