Effect of racing on blood variables in Standardbred horses

Blood is collected for hematologic and biochemical analyses when racehorses perform poorly. However, racing affects most analyte levels; therefore, the timing of blood sampling can affect analyte levels and interpretations.

This study aimed to determine if the blood variable levels returned to pre-racing levels 2 and 3 days post-racing.

Blood was sampled from 17 healthy racehorses pre- and post-racing. The variables measured from plasma were albumin, cholesterol, creatinine, calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), creatine phosphokinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT), and cortisol. Hematocrit (HCT), hemoglobin (HGB), white blood cell (WBC), red blood cell (RBC), granulocyte, and lymphocyte counts were analyzed from blood collected in EDTA-coated vials.

Calcium was lower 3 days post-racing compared with 2 days pre-racing (P < 0.01), P and GGT were higher 2 and 3 days post-racing compared with those at the pre-racing timepoints (P ≤ 0.01), and RBC, HCT, and HGB were higher 2 days post-racing compared with those at the pre-racing and 3-day post-racing time points (P < 0.01, all).

A few blood biochemical and hematologic variables were significantly altered 2 and 3 days post-racing. The level of these changes did not affect the clinicopathologic interpretation of the values.