Cortisol and haematochemical variables of horses during a two days trekking event: effects of preliminary transport

REASONS FOR PERFORMING STUDY: Trekking is a noncompetitive sport, involving maximal skeletal muscle effort. Exercise and transport may involve significant energy expenditure and give rise to substantial stress. Few studies have examined the combined effect of exercise and additional preliminary transport on adrenocortical and haematochemical responses in horses during trekking. OBJECTIVES: To ascertain whether exercise and additional preliminary transport before trekking would affect the circulating cortisol levels and haematochemical variables of horses during a 2 day trekking event. MATERIALS AND METHODS: Twenty-nine healthy horses were used. Twenty-four horses were transported over distances of 70 km the day before trekking and 5 horses were stabled at the starting place. Blood samples were taken from horses at 16.00 h the day before trekking; and at 08.30 h and 17.30 h before and after the first day of trekking; at 08.30 h and at 13.30 h before and after the second day of trekking. Serum cortisol and haematochemical variables were determined in duplicate by using commercial test kits. One-way analysis of variance for repeated measures (RM-ANOVA) was applied to determine whether trekking and transport had any effects. RESULTS: Trekking significantly (P < 0.01) affected total protein, albumin, urea, aspartate aminotransferase (AST), alanine aminotransferase (ALT), PCV and cortisol changes in transported horses and only urea and PCV (P < 0.01) changes in untransported horses. Untransported horses showed lower basal total protein (P < 0.05) and albumin (P < 0.01) concentrations, higher urea concentrations (P < 0.001) at the second day and lower cortisol levels after the first and the second (P < 0.05) day of trekking than transported horses. CONCLUSION: These data show that the preliminary transport stress induced additional significant changes of cortisol and haematochemical patterns in horses after trekking.