Acid:base and serum biochemistry changes in horses competing at a modified 1 Star 3-day-event.

The research study explored the changes in hydration, acid-base status, and electrolyte balance in horses participating in different modifications of Day 2 of a 3-day event. The results indicated metabolic acidosis with a compensatory respiratory alkalosis, a reduction in total body water and cation content, and hypocalcaemia among all groups, with no significant differences detected across modifications.

Participation in Event Modifications and Its Effects

The study involved three groups of horses, including 8 European horses and two sets of 9 North American horses. These horses completed identical activities on Day 1 (dressage) and Day 3 (stadium jumping) of a 3-day event. The differences were on Day 2, where some horses performed modifications of a 1 Star 3-day event, while others participated in Horse Trials.

• The jugular venous blood of each horse was collected on the morning of Day 2, between 4 min 55 s and 5 min 15 s after Phase D, and the following morning.
• It turned out that eight European horses, five TD horses, and eight HT horses completed the trials.

Observations on Acid-Base and Serum Biochemistry Changes

The researchers found few significant differences in acid-base or serum biochemistry variables among horses performing either two variations of the Speed and Endurance day of a 1 Star 3-day event or a conventional Horse Trial:

• The lack of significant differences could have been due to low statistical power associated with the small number of horses (especially in the TD group), variation in horse quality among groups, and E horses competing at different times of the day.
• Despite these, there were common changes observed in all horse groups, such as metabolic acidosis coupled with a compensatory respiratory alkalosis, a reduction in total body water and cation content, and hypocalcaemia.
• Of note, all horse groups failed to replenish their deficits in cation, chloride, and calcium, even after 14-18 hours of recovery.

Implications

The study offers valuable insights into the physiological responses of endurance horses, indicating the need for appropriate interventions to support their hydration and electrolyte balance. However, the findings need to be treated with caution, given potential factors impacting the results, such as the small sample size and variable quality among horse groups.