Metabolic response to standardised exercise test in standardbred trotters with red cell hypervolaemia.

The research investigates how Standardbred trotters with red cell hypervolaemia (an above-normal volume of red blood cells) respond to a standard exercise test. It was found that these horses display very similar behaviours to those with a normal volume of red blood cells, although there were distinctions in certain metabolic responses, suggesting a higher rate of amino acid use in energy production.

Objective of Study

• The researchers aimed to understand the metabolic response of Standardbred trotters, particularly those with a condition known as red cell hypervolaemia, to standardised exercise tests. This condition is characterized by an above-normal volume of red blood cells.

Research Methodology

• The study involved 29 Standardbred trotters that were subjected to a standardized incremental exercise test.
• The horses were categorized into two groups based on their red blood cell volume – those with normal volume (normovolaemic) and those with higher than normal volume (hypervolaemic or polycythaemic).
• Various plasma concentrations including lactate, amino acids, ammonia, and products of purine catabolism were tested before, during, and after the exercise.

Findings and Conclusion

• The researchers found that the exercise-response curve for taurine, an amino acid, was significantly different between the two groups. The rest of the amino acids, however, exhibited similar behavior in both groups.
• The ratio between branched-chain amino acid and alanine, which is considered a marker for the use of amino acids in gluconeogenesis (the formation of glucose from non-carbohydrate sources), was significantly higher at rest in the polycythaemic horses.
• The concentrations of ammonia and allantoin, end products of ATP (the primary energy source for cellular functions) breakdown, were found to be lower in the horses with red cell hypervolaemia.
• However, other markers for lactate and heart rate responses, oxidative capacity of a certain muscle, enzyme activities, and post-exercise concentrations of lactate, uric acid, and hypoxanthine showed no significant differences between the two groups.
• Based on these results, the researchers concluded that horses with red cell hypervolaemia generally behave similarly to normovolaemic horses during a submaximal standardised exercise test.
• The findings suggest that polycythaemic horses may have an increased rate of utilizing amino acids in gluconeogenesis and a possibly heightened ability to produce energy aerobically.