Hepatic blood flow in horses during the recuperative period from maximal exercise.

This research investigates the effects of walking or standing on horses’ liver blood flow after brief, intense exercise. The study found that after exercise, the hepatic blood flow and pharmacokinetics of BSP, a drug used to measure liver function, changed significantly in the horses. However, restricting the horse’s movement after exercise did not have any significant impact on the hepatic blood flow.

Objective and Methodology

The main goal of this research was to explore the impact of walking or standing still on hepatic (liver) blood flow in horses following brief, high intensity exercise. Six Thoroughbred horses were first conditioned on a treadmill to uniform fitness levels. Post this, each horse was asked to follow a specific treadmill speed that would cause it to exercise at 120% of maximal oxygen consumption. This was used in simulated races at 14-day intervals. These exercises lasted until the horses were fatigued, or for a maximum of 2 minutes.

• The horses then underwent three interventions: resting on the treadmill (REST), exercising before standing on the treadmill for 30 minutes (MS), and exercising then walking at 2 m/s for 30 minutes (MW).
• A minute after completion of each exercise, bromsulphalein (BSP), a compound often used in determining liver function, was infused intravenously into the horses.
• Blood samples were then taken every two minutes for half an hour to analyze BSP concentration, while hematocrit and plasma total solids concentration were measured.

Results

The study found that plasma BSP concentration increased following exercise. Correspondingly, median hepatic blood flow, represented as BSP clearance, experienced a significant drop from 23.8 (REST) to 20.7 (MS) and 18.7 (MW) ml/min/kg. Additionally, the median steady-state volume of distribution of BSP decreased from 47.6 (REST) to 42.7 (MW) and 40.2 (MS) ml/kg. Notably, whether the horses walked or stood after exercise, the differences between trials were not significant.

Conclusions

The research concludes that hepatic blood flow and the pharmacokinetics of bromsulphalein are significantly altered immediately after high-intensity exercise in horses. However, limiting the horse’s movement post-exercise, whether by standing or walking, did not appear to substantially impact hepatic blood flow. Further study could be beneficial to ascertain the overall effects of exercise on hepatic function, and how best to support recovery post-exercise.