Plasma aldosterone concentration and cardiovascular response to low sodium intake in horses in training.

The research study investigates how low sodium intake impacts athletic horses’ cardiovascular system and also discovers potential indicators of low sodium intake. The study’s main finding indicates that five weeks of low sodium intake led to elevated plasma aldosterone concentration and packed cell volume (PCV), with no heart function changes observed.

Research Methodology

The researchers conducted this study with seven Standardbred geldings, or castrated male horses, in training. These horses were fed a standard diet either supplemented with sodium chloride (NaCl) or not. The horses were examined over five weeks, and the diet was provided in a changeover design — an active form of controlling and eliminating potential lurking variables.

• A variety of data was collected for the study. Blood samples were taken weekly and before and after a workout in the final week to analyze various parameters such as blood sodium levels, total plasma protein, plasma aldosterone, troponin I, and packed cell volume.
• Blood pressure and pulse wave were recorded at rest using a high-definition oscillometric technique. Furthermore, an ECG and echocardiography were recorded to monitor the heart’s activity and structure.
• Other measurements included the water intake before and on the exercise day, along with voluntary saline intake for two days following each period. Moreover, the faecal matter was sampled weekly for sodium and potassium content analysis.

Findings and Conclusion

• The results proved that plasma aldosterone and packed cell volume were higher in the group that did not receive additional sodium supplementation. These outcomes indicate changes in hormone levels and blood composition due to low sodium intake.
• Interestingly, there were no significant variations in blood pressure, ECG readings, plasma troponin I levels, and echocardiogram data between the two diets. However, a slight tendency towards a smaller high-definition oscillometric pulse amplitude was observed on the low sodium diet.
• This study illustrates that a water intake reduction and increased saline intake occurred on the low sodium diet. Additionally, the response to exercise in terms of blood sodium, plasma aldosterone, PCV, and total plasma protein varied under the two different diets.
• The faecal potassium/sodium ratio was higher on the low sodium diet, suggesting that this ratio could be a potential marker for assessing a horse’s sodium status.

In conclusion, the study indicates that a low sodium intake over five weeks can increase plasma aldosterone concentration and PCV in horses without affecting heart function. The research brings light to a new potential way of assessing sodium status in horses through the faecal potassium/sodium ratio.