A comparison of grain, oil and beet pulp as energy sources for the exercised horse.

This research investigates the impact of three different diets on the exercising horse, focusing on high-grain diets, diets with 15% intake from vegetable oil, and diets with 15% intake from beet pulp – a highly fermentable fibre source. The results show that substituting 15% of digestible energy (DE) in the horse’s diet with vegetable oil had a more significant effect on the horse’s metabolic response to exercise than a 15% substitution with beet pulp.

Methodology

• Six 3-year-old Thoroughbreds were picked for the study and fed one of the three specific diets over a period of 5 weeks. The experiment was based on a replicated 3 x 3 Latin square model, a statistical method widely used in scientific trials.
• The CONTROL diet consisted of 3.65 kg of sweet feed (SF), 0.9 kg of a protein/vitamin/mineral pellet, and 5.45 kg of hay cubes.
• The FAT diet replaced 1.15 kg of SF with 0.45 kg of soybean oil, and the FIBRE diet replaced 1.15 kg of SF with 1.36 kg of beet pulp.
• The horses were exercised 3 times a week on a high-speed treadmill and a standardised exercise test (SET) was carried out in the final week of each period.
• A series of blood samples were taken before feeding and every 30 minutes for 3 hours post-feeding, throughout the exercise bout, and 30 minutes after exercise.

Findings

• Levels of lactate, glucose, cortisol, insulin, packed cell volume, total protein and triglycerides in the horse’s plasma were analysed.
• Post feeding, horses in the FAT-fed group showed lower blood glucose compared to the CONTROL and FIBRE-fed horses and lower insulin post feeding and throughout exercises.
• Cortisol levels were lower in the FAT-fed horses during exercise compared to the CONTROL-fed horses.
• Post-exercise water intake was significantly higher in the FAT-fed horses creditable to faster rehydration.

Conclusion

• The results indicate that substituting 15% of DE in the diet with vegetable oil had a more noticeable impact on the metabolic response to exercise in horses than a similar substitution with beet pulp.
• This may potentially suggest that the source of energy in a horse’s diet can have substantial effects on its performance and metabolism during and after exercise.