Metabolomic investigation of exercise-induced response to moderate and high intensities training sessions in Thoroughbred flat racehorses

The training program of Thoroughbred (TB) flat racehorses includes exercise sessions of low to high intensities, short to long distances and rest periods. This field study aimed at assessing the metabolic responses induced by two training sessions of different intensity, widely used in the training of TB.
Blood samples were collected in two groups of six and five TB at rest and 30 minutes after a high-intensity (gallop, 1.400m) and a moderate intensity (canter, 2.500m) exercise, respectively. Plasma samples were analyzed using an untargeted metabolomic approach based on liquid chromatography coupled with mass spectrometry. Exercise intensity was evaluated by monitoring heart rate and speed as well as exercise-induced changes of targeted biochemical parameters (e.g. lactatemia, hematocrit, etc.). Unsupervised principal component analysis performed on all detected features revealed changes in metabolome from pre- to post-exercise plasma samples with a greater extent following high-intensity exercise. In addition, supervised analyses revealed changes of 172 features by high-intensity exercise, among them 35 metabolites were identified using standard metabolites comparisons. These metabolites were mainly related to the chemical class of amino acids, nucleic acids and vitamins. Moderate intensity exercise induced changes of only a few metabolites, related to lipids and amino acids. In conclusion, TB training sessions induce differential changes in energy pathways depending on the intensity and the distance of the exercise.