Effects on exercise metabolism of varying dietary starch and sugar proportions.

The research is about the effects of diets with differing starch and sugar compositions on the exercise metabolism of horses. The finding suggests that horses consuming high sugar diets show an increased heart rate during low-intensity exercise, and their response in oxygen uptake and the ratio of carbon dioxide produced to oxygen consumed varies depending on the intensity of the exercise.

Methodology of the Study

• The test subjects of this study were 4 Standardbred horses. These horses were chosen to participate in a crossover experiment where their diets were manipulated to assess the metabolic effects during exercise.
• The horses were fed a basic diet of hay and oats, with the oats being gradually substituted with barley syrup (BS) at four different levels (0, 0.5, 1.0 and 1.5 kg). The increase in barley syrup represented an increase in the sugar content in their diet.
• Each specific diet was given to the horses for 21 days.
• After the 21-day period, the horses underwent two types of exercise tests: an incremental treadmill exercise test (IE) and a 40-minute submaximal exercise test (SE).

Results of the Study

• During the incremental exercise, there was a significant increase in mean VO2 (oxygen uptake) on the highest proportion of BS (1.5 kg). Additionally, the respiratory exchange ratio (RER), which is a marker for substrate utilization, was notably lower when the horses were on BS levels 1.0 and 1.5.
• In the case of submaximal exercise, both respiratory exchange ratio and heart rate were significantly higher when the horses fed BS levels 1.0 and 1.5.
• The diets had no significant effects on plasma levels of glucose, lactate, and insulin.
• After the submaximal exercise, the muscle glycogen content significantly decreased on the diet with no BS (BS 0). However, this decrease was not observed in the other diets with some proportions of BS.
• Trends suggested that glycogen utilization during submaximal exercise decreased as the daily sugar intake in the diet increased.

Conclusion and Further Research

• The study concludes that high sugar intake in horses’ diets might impact their metabolic response during exercise. Notably, it increases their heart rate during less intensive exercise.
• Metabolic responses including oxygen uptake and respiratory exchange ratio change depending on the intensity of the exercise and potentially the amount of sugar in the diet.
• The research suggests that sugar intake might have an influence on reducing glycogen utilization during submaximal exercise.
• Further research is required to evaluate if such a feeding strategy could be beneficial, particularly for horses competing in endurance distances where energy management and utilization are key.