Glycemic index of a meal fed before exercise alters substrate use and glucose flux in exercising horses.

The research article studies how the type of meal fed to horses prior to exercising impacts the use of different energy sources and glucose levels in the animals. It particularly compares the effects of feeding corn, alfalfa, and no feed.

Article Summary

The study conducted experimented on six adult horses in good health conditions. The horses were made to run on a treadmill at half of their maximum oxygen consumption rate for a duration of 60 minutes. This process was carried out after the horses were denied access to food for 18 hours and were then subject to one of the three different feeding interventions: fed with corn, fed with an isocaloric amount of alfalfa or were not fed anything prior to exercise. The test was randomly assigned in a balanced, crossover study.

• Outcomes showed that corn feeding, compared to fasting, led to higher levels of plasma glucose and serum insulin, and lower serum nonesterified fatty acid concentrations before the onset of exercise. During the workout, there was an increase in skeletal muscle utilization of blood-borne glucose with lower resulting plasma glucose, serum glycerol, and serum nonesterified fatty acid concentrations.
• When comparing corn feeding to alfalfa pre-exercise, findings indicate that corn resulted in higher carbohydrate oxidation and lesser fat oxidation during the exercise.
• The study concludes that feeding a soluble carbohydrate-rich meal (i.e., corn) prior to exercise enhances muscle utilization of glucose taken through the bloodstream and carbohydrate oxidation, as well as decreases fat oxidation in comparison to an insoluble carbohydrate meal (i.e., alfalfa) or no feeding before exercise.
• However, the carbohydrate feedings did not provide a muscle glycogen sparing effect in comparison to fasting.

Significance of Research

This research provides important insights into the dietary planning of horses, especially athletic ones. The kind of feed given pre-workout has significant effects on the energy sources used during the workout and the resultant glucose levels. Feeding soluble carbohydrate-rich meals boost muscle use of blood-borne glucose and carbohydrate oxidation at the expense of fat oxidation compared to not feeding or feeding insoluble carbohydrate meals. Further study can help shape dietary recommendations for athletic horses.