Changes in Salivary Cortisol Concentration in Horses during Different Types of Exercise

This study aimed to estimate the change of stress level in horses based on cortisol concentration levels in their saliva. A total of 61 horses were divided into the following three groups: i) tourist riding experience (TR, n = 23); ii) resting group (RR, n = 14); and iii) horse-riding education (ER, n = 24). The saliva samples of TR and ER groups were taken using plain cotton Salivettes four times a day: at 07:00 (basal), 11:00 (Exercise 1, after 1-hour exercise in the morning), 14:00 (Exercise 2, after 1-hour exercise in the afternoon), and 16:00 (Exercise 3, after 1-hour exercise in the afternoon). The saliva samples of RR were measured at the same time. The samples were analyzed using the SAS program general linear model procedure. In a percentage relative to the base value, cortisol levels in Exercise 3 were confirmed to decrease in all groups as compared to the basal value percentage in the following sequence: ER>TR>RR. The highest peak was confirmed in Exercise 2 (approximately 131%) of RR group and the lowest peak appeared in Exercise 3 (approximately 52%) of ER group. Therefore, resting without any particular exercise can also increase the stress level of horses. Thus, it is better to exercise, as exercise can reduce the stress level, even in cases when riders are clumsy or lack appropriate horse-riding experience. The results of the present study are useful to equestrian center owners and educational riding instructors in that they provide a meaningful insight into a better horse management.