Research Project Manager Equine Pharmacology Lab, Penn Vet, New Bolton Center Kennett Square, Pennsylvania, United States
Abstract: Background Elevated plasma levels of gamma-glutamyl transferase (GGT) are frequently seen in Thoroughbred racehorses and are thought to be associated with increased training workload and poor performance.
Hypothesis: Recent training workload and current racing status influence plasma GGT levels in Thoroughbred racehorses.
Animals 181 venous blood samples were obtained from 60 Thoroughbred racehorses in training (28 females, 16 intact males and 16 geldings, aged 1-7 years, mean: 3.1 ±1.2 years).
Methods Samples were obtained 1-4 hours after morning workouts on a non-race day. Age, sex, whether the horse was racing (R) and number of days since last raced (DLR) was recorded. Maximum training workload on the morning of sampling (WLAM) and during the previous week (WLWK) was obtained for 131 and 90 samples respectively. Workload was categorized: none/walk/jog/gallop/breeze/race. Plasma was analyzed for GGT concentration using a Vitros XT 3400 chemistry system (Ortho Clinical Diagnostics, NJ, USA). Stepwise regression was used to identify which parameters significantly influenced GGT, then a multivariable mixed-effects regression model was used to analyze fixed effects at the level of horse nested within trainer.
Results Median plasma GGT was 47 U/L (range: 17-142). GGT was above laboratory reference range (45 U/L) in 100/180 samples and in at least one sample from 35/60 horses. Plasma GGT levels were significantly affected by DLR and WLWK (Table 1) but not age, sex, R or WLAM (Figure 1).
Conclusion Preliminary findings indicate further investigation of the effect of workload and performance metrics on plasma GGT levels in Thoroughbred racehorses is warranted.
