Trot asymmetry in relation to physical performance and metabolism in equine endurance rides.

This research article explores how trot asymmetry in endurance horses changes throughout a competition, its potential connection to the horse’s metabolism, and if it can be used to distinguish between different performance levels of horses.

Background and Objective

• This study investigates trot asymmetry, which is an irregular gait that may occur or intensify in horses during endurance races due to factors like pain, lameness, or extreme fatigue.
• The research aims to determine if trot asymmetry increases during endurance competitions, to see if it can differentiate between horses with varying performance levels, and if it relates to metabolism.

Methods

• Fifty-eight horses were filmed walking at a trot during the lameness exams in the vet-gates, before the competition and after specific phases (at 29 km, 59 km, and the end at 80 km).
• The stride duration (SD) of all four limbs was measured, and a Locomotion Symmetry Index (LSI) was calculated by comparing the stride duration in the diagonal pairs of limbs. Horses were classified as symmetric (SyH) or asymmetric (ASyH) based on this index, relative to before the competition.
• Venous samples were taken from the horses at the vet-gates and various parameters such as White Blood Cell (WBC) count, creatinine, Total Plasma Protein (TPP), uric acid, Creatine Kinase (CK), LDH, Sodium (Na), Potassium (K), Chloride (Cl), and PCV were measured.
• The horses were divided into groups based on their performance: successful (SH), lame (LH), and metabolic (MH). The successful group was further divided into faster finishers (FF) and slower finishers (SF).

Results

• Most of the horses remained symmetric in their trot (>80%), with little variation between different performance groups.
• Asymmetry increased at the vet gates, particularly in the lame and metabolic horse groups.
• Negative correlations were observed between LSI and velocities during the rides, in the vet gates, and CK levels.
• Horses exhibiting asymmetry had higher velocities during the rides and plasma CK levels, and lower speeds at the vet-gates and plasma uric acid concentrations.

Conclusion

• Despite the increase in trot asymmetry during endurance events, the Locomotion Symmetry Index, calculated by comparing stride duration in the two diagonal pairs of limbs, was not effective in distinguishing horses with different performance levels.