Effects of novelty stress on neuroendocrine activities and running performance in thoroughbred horses.

This research article describes a study that looked into how stress from new experiences affects the hormone activity and running performance of thoroughbred horses. The research discovered that novel stimuli reduced certain stress responses and improved performance during high-intensity exercise.

Overview of the Study and Its Methods

The researchers investigated how novelty stress, or stress from new experiences, affects the hormones and running performance in thoroughbred horses. To do this, they exposed the horses to two types of new experiences: novel audiovisual stimuli and novel field stimuli. After exposure to the new stimuli, they observed changes in the plasma concentrations of several hormones and in heart rates.

• The hormones they monitored included vasopressin, catecholamines, and adrenocorticotropin (ACTH).
• They also conducted experiments to observe the neuroendocrine activities during incremental exercise and during supra-maximal exercise, which involves working at 110% of their maximum heart rate.

Findings of the Study

The study found several notable results related to how novelty stress affects hormone levels and running performance in horses:

• The researchers found that after exposure to new experiences, the plasma concentrations of vasopressin, catecholamines, ACTH, and the heart rates of the horses all significantly increased.
• During both types of exercises, it was found that plasma concentrations of vasopressin, catecholamines, ACTH, and also blood lactate, increased as the exercise load increased.
• However, when horses were presented with new stimuli during supra-maximal exercise, the increases in plasma vasopressin and catecholamines were significantly smaller compared to controls. Blood lactate was also significantly lower and total running time until exhaustion was longer than control experiments.

Interpretation of the Study

Based on their results, the researchers proposed that exposure to new stimuli can activate the release of vasopressin from the posterior pituitary gland, in addition to activating the sympatho-adrenomedullary and the hypothalamic-pituitary-adrenocortical axes in thoroughbred horses. This seems to result in an increased exercise capacity and improvement in running performance during high-intensity, or supra-maximal, exercise. Their findings suggest that new stimuli, or novelty stress, may potentially be used as a tool to improve the performance of racehorses.