Biochemical changes in three-day-event horses at the beginning, middle and end of Phase C and after Phase D.

The research studies the biochemical changes in horses undertaking a three-day endurance event. Blood samples were collected from the horses at various points and studied to understand how strenuous activity impacts the horses’ health.

Methodology

• The study involved 36 horses that participated in a three-day event at the CCI* (n = 19) or CCI** (n = 17) level.
• Blood samples were extracted at various phases – 12-16 hours before the speed and endurance test, immediately after the steeplechase, midway and at the end of Phase C, and immediately after cross-country.
• These blood samples were then analyzed for a range of chemical levels – including Packed Cell Volume (PCV), sodium, potassium, chloride, ionized calcium, pH and lactate, plus certain serum concentrations such as protein (TP), albumin, calcium, alkaline phosphatase (AP), gamma glutamyl transferase (GGT), creatine kinase (CK), aspartate aminotransferase (AST), glucose, and creatinine.

Results

• The analysis showed no significant difference between the biochemical measurements between the CCI* and CCI** horses at any sampling time. This was surprising given the differences in speed and length of various phases of the speed and endurace test.
• There was, however, a significant change over time across all horses (n = 36) in the biochemical parameters.
• The levels of PCV, calcium, potassium, lactate, total protein and albumin concentrations significantly increased after Phase B, then decreased towards pre-exercise levels during Phase C, thus supporting the belief that Phase C is a recovery phase.
• Contrarily, chloride levels decreased, while creatinine and CK levels increased from the end of Phase B to the end of Phase C. This change most likely resulted from fluid loss through sweat, reduced blood flow to the kidneys, and continued muscle activity.

Conclusion

• Many of the biochemical parameters remained mostly static between the midway point and the end of Phase C.
• However, there were some exceptions. Potassium, chloride, lactate, and glucose levels decreased, while pH and creatinine levels increased significantly from the midway point to the end of Phase C.
• The most notable advantage of the additional distance from the midway point to the end of Phase C was a further reduction in lactate concentrations before the commencement of Phase D.

This study’s results provide a valuable insight into the physiological demands on horses during strenuous three-day events and could contribute to improving care and management of these animals during such activities.