Electrocardiography, Heart Score, and Hematology of Horses Competing in an Endurance Ride.

The study examines the physiological changes in horses competing in a 100-kilometer endurance ride, focusing specifically on heart activity, heart scores, and the levels of dehydration reflected in the packed cell volume (PCV) and total plasma protein (TPP).

Study Design and Methodology

The research involved thirty-one horses which participated in an endurance ride spanning 100 kilometers. To understand the effect of the ride on the horses, their physiological data was collected at different stages:

• Electrocardiograms (ECG) were recorded before the start of the ride and at the finish to measure the cardiac activity of each horse.
• The heart score, an index of cardiac output or the heart’s efficiency, was calculated based on the ECG data,
• Blood samples were taken prior to the start, at the 60-kilometer mark (mid-ride), and at the completion of the ride to determine the PCV and the TPP levels. PCV reveals the proportion of blood volume occupied by red blood cells, where higher values often indicate dehydration, while TPP provides insight into levels of proteins in the blood plasma.

Findings and Interpretation

Two key observations emerged from the analysis of the collected data:

• Horses which completed the ride at a faster pace had significantly higher heart scores when compared to the slower group or those eliminated due to insufficient recovery of heart rate. This suggests that higher heart efficiency or output was associated with faster completion of the endurance ride. However, it should be noted that no horses developed any abnormalities in their ECG as a direct result of participating in the ride.
• Analysis of the PCV levels suggested that all horses experienced levels of dehydration during the ride. The faster group of horses had notably higher PCV values and heart rates both mid-ride and at the end of the ride. This implies that faster paced horses may experience more dehydration. But, when examining TPP values, no significant differences were found between the different groups of horses. This indicates that while faster speeds may contribute to higher dehydration levels, it does not significantly affect protein levels in the blood.

This study offers significant insights into the physiological changes that occur in horses during endurance rides and can be a valuable resource for optimizing their training and racing performance while ensuring their welfare.