The purpose of this study was to assess the stress responses associated with vaquejada simulating tests (VSTs). Ten clinically healthy 8.9 ± 4.3-year-old Quarter horses, weighing 441.3 ± 25.0 kg, performed two VSTs five days apart. In the first VST (M1), animals ran three times with a 5-min rest between races; and in the second (M2), they ran with a 15-min rest between races. Horses were examined before (T0) and immediately after the third run (T1) and at 4 h (T2) of recovery. Stress biomarkers included heart rate (HR), heart rate variability (HRV), cortisol, and white blood cell count. All variables were analyzed by ANOVA and Tukey tests, considering p p = 0.0463) and helper (p = 0.0349) horses when they had a 15-min rest between races. The rMSSD and mean R-R values for helper horses were also significantly lower in M2. In conclusion, the 15-min rest interval proved to be better than the 5-min period for both categories of equine athletes used in vaquejada mainly for helper horses. A longer rest time between races allowed the organic recovery necessary for these animals to impose a greater applied physical effort load, which is a fact that guarantees good performance and well-being.
