The Potential Role of Training Sessions on the Temporal and Spatial Physiological Patterns in Young Friesian Horses

Circulating ACTH and Cortisol Investigations in Standardbred Racehorses Under Training and Racing Sessions

The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system involved in the coping response to stressful challenges during exercise stimuli. Exercise represents a significant disruptor of homeostasis, inducing an ACTH-cortisol co-secretion, based on different characteristics of exercise in sport horses. Based on this statement, the aim of this study is to evaluate the circulating adrenocorticotropin and cortisol changes in Standardbred trotters, after training and racing sessions, considering the different age and sex. In particular, the aim is to determine to what extent the level of ACTH and cortisol increases during maximum effort in competition conditions (racing), and to compare two exercise conditions of different intensity, training and racing sessions, and effects on ACTH and cortisol responses. Ten Standardbreds, three females and seven males, clinically healthy, were enrolled and subjected to two exercise conditions: a non-competitive session (training) and then a competitive event (racing). Four of them were 2-year-olds and a further six were 3-year-olds. Training and racing effects on both ACTH (p < 0.01) and cortisol (p < 0.01) values were obtained. Compared to the training session, horses showed greater ACTH concentrations at rest (p < 0.001), at 5 (p < 0.01) and 30 min (p < 0.001), and lower cortisol concentrations only at rest (p < 0.01) after racing; 2- and 3-year-old horses showed the greater ACTH concentrations at 5 and 30 min (p < 0.01) post-racing; males showed the greater ACTH concentrations at 5 min and 30 min (p < 0.01) post-racing. The different stimuli of the two contexts, and differences in exercise intensity, such as training and competitive event, may have affected the direction of hypothalamic-pituitary-adrenal (HPA) axis response, both as an ability to adapt to physical stress of different intensity and as a preparatory activity for coping with stimuli. In conclusion, training and racing events induced a different HPA axis response in which both emotional experience and physical maturity could induce a significant adaptive response. As ACTH and cortisol concentrations in adult equids are extremely heterogeneous, further investigation is required to explore how different variables can influence the hormonal dynamics and their role as expressions of adaptive strategies to stress in horses.

Does Experience Make Hucul Horses More Resistant to Stress? A Pilot Study

The aim of the study was to determine whether experience related to horse age and number of starts in championships influences stress level, measured by salivary cortisol concentration. The study involved 18 clinically healthy Hucul mares who participated in the Polish Championships for Hucul Horses. Evaluation of performance value was carried out in accordance with the guidelines specified in the breeding and genetic resources conservation program for this breed. The championship lasted two days, consisting of conformation evaluation, endurance, and Hucul path. Saliva was collected at baseline (T1), after arena assessment (T2), after endurance (T3), and on the second day after the Hucul path (T4). Cortisol levels increased from an average of 2.73 ± 1.18 ng/mL (T1) to 10.46 ± 8.03 ng/mL after T3. Significantly lower levels of free cortisol were detected in the saliva of the younger mares, up to 9 years old, and mares who participated in only one qualifying path after each element of the championship. The highest levels of cortisol (T3) were found in mares competing repeatedly on the qualifying path. No correlation was found between cortisol levels and the championship results. Participation of mares in the championship was associated with stress, which was reflected in the increase in cortisol levels in saliva.