Effects of breaking, starting and training sessions on adrenocortical responses of Arab horses

Breaking and starting represent critical phases of human-horse interaction. Aim of this study was to evaluate whether breaking, starting and training sessions had different effects on post-exercise circulating cortisol changes of eight healthy Arab horses (3 males, 5 females), 1-3 years old. Group I: (2 males, 2 female horses) submitted during two consecutive weeks on alternate days to breaking sessions, represented by 60 min exercise performed with rope on a round track (10 min walk, 10 min trot in a clockwise direction; 10 min walk, 10 min trot in an anti-clockwise direction; 10 min walk, 10 min trot in a clockwise direction). After a week, they were submitted during two consecutive weeks on alternate days to starting sessions, represented by 60 min exercise performed with rope and thorax belt, as described before. Group II: (1 male, 3 female saddled horses) submitted during two consecutive weeks to daily training sessions, represented by 60 min exercise performed with the same rider on a round track (10 min warm-up with rope, 10 min walk, 10 min trot, 5 min gallop, 10 min trot and gallop and 15 min winding-down exercises). Blood samples were drawn three times a week before and 5 and 30 minutes after sessions. Circulating cortisol levels were determined in duplicate using a commercially available immunoenzymatic kit supplied by RADIM (Pomezia, Italy). Statistical analysis were carried out by 1-way RM-ANOVA and Student’s paired and unpaired t-test. Compared to basal, higher not significant cortisol levels were observed both at 5 (+7.00 %) and 30 (+5.80%) min after breaking sessions; lower not significant cortisol levels were observed both at 5 (-10.80 %) and 30 (-16.40%) min after the starting sessions; significant higher cortisol levels were observed both at 5 (+68.60 %; p<.001) and 30 (+139.40%; p<.001) min after the training sessions. RM-ANOVA showed a significant effect of training on circulating cortisol changes (F=96.67; p<.0001). No significant differences in basal values were observed. Circulating cortisol levels were significantly lower at 5 (p<.001) and 30 (p<.005) min after the breaking and starting sessions than after the training session. No significant differences were observed according to different age and gender. LP Data showed that workload stress of breaking and starting sessions was the same, without significant changes on cortisol levels; the workload stress of training sessions resulted the highest, in according to daily exercise, with significant post-exercise increases of cortisol levels. The psychophysic reactivity during breaking and starting sessions was lower than during training sessions.