Hydration and electrolyte balance in horses during an endurance season.

This study investigated the effects of endurance training and racing on the hydration and electrolyte balance of horse. It found that several aspects of horse’s blood composition and urine altered significantly during training and long distance endurance races.

Methodology

• The researchers gathered blood and urine samples from eight endurance horses during periods of rest, before any training had started. They then took additional samples after two different 11-week training periods, labelled T1 and T2.
• Following each training period, they had the horses participate in a 120 km endurance ride, sampling before, during and 2 hours after each ride.

Testing Process

• They analysed the blood samples for packed cell volume (PCV), total protein (TP), urea, creatinine, and electrolyte concentrations.
• The urine samples were tested for pH, specific gravity, creatinine, and electrolyte concentrations. This information allowed the team to calculate the fractional excretion of electrolytes (FE), a measure of how well the kidneys are regulating electrolyte concentrations.
• Any changes that could be linked to the training or endurance rides were statistically analysed using a Student paired t test.

Results

• The study found that the horses’ blood concentration of total protein, urea, creatinine and sodium increased during the T1, while the PCV, a measure of the concentration of red blood cells in the blood, decreased significantly in T2.
• The fractional excretion of chloride (FE(Cl)) in urine increased during the first training block and then fell afterwards. The fractional excretion of potassium (FE(K)) however, increased significantly during both training periods.
• During the endurance rides, an increase was noted in PCV, plasma total protein, urea, creatinine and total Calcium concentrations while plasma Sodium and Chloride concentrations decreased.
• There were also changes in the horses’ urine with decreases in Sodium, Potassium and Chloride concentrations, as well as the fractional excretion of these electrolytes. On the other hand, urinary creatinine increased.

Conclusion

• This study offers new insights into how endurance training and prolonged exercise can alter levels of hydration and electrolyte balance in horses.
• The conclusions derived from this study could contribute to the strategies used to prepare and care for horses in endurance training and racing, particularly in terms of managing their hydration and electrolyte balance.