Is it a good idea to train fillies and colts separately?

This study compared the physiological response to novel situations in sex-separated and sex-mixed groups of horses, as measured by heart rate (HR). The study evaluated the possibility of training horses in a mixed-sex system. The study included 41 Purebred Arabian 2½-year-olds during their first walk on an automated horse walker. Four groups, divided by manner of care and training, consisted of 10 colts and 10 fillies kept in separate stables and trained in separate male or female groups and 12 colts and 9 fillies kept in the same stable and trained together. The study measured HR when horses were at rest before exercise, while moving from stable to walker, during 30 min of exercise on walker, while moving from walker to stable, and at rest after exercise. Mean HR scores recorded from training on the walker were higher in sex-mixed groups. Results obtained while horses were moving from stable to walker, then from walker to stable, were significantly higher in the sex-mixed groups. The study did not recommend training young horses in sex-mixed groups.