Performance of acclimatized European horses in a modified one star (*) three-day event in heat and humidity

The physiological and biochemical responses of previously acclimatized European three-day event horses to competition in hot humid conditions were investigated. Four Thoroughbred (TB) and four non-Thoroughbred (NTB) horses were flown from Europe to Georgia (USA), underwent a three-week period of acclimatization, and then took part in a modified FEI One star Three-Day Event. The speed and endurance test was modified in an attempt to compensate for the environmental conditions to reduce thermal stress; these alterations included reduction of Phase A, a 10 min
cooling stop on Phase C and extension of the 10 min box to 12 min to permit a test to be performed in order to obtain a cardiac recovery index (CRI). Non-Thoroughbred horses were significantly heavier than Thoroughbred horses (591 ± 31 versus 522 ± 17 kg; P<0.02). There were no significant differences in any other characteristics between TB and NTB and only minor differences in variables measured or recorded at rest or during competition. Final competition placings of TB were not significantly different from NTB. None of the horses suffered any heat-related condition at any time before, during or following the field trial. All horses returned to Europe and no medical consequences were reported to occur subsequently in relation acclimatization or competition.