Effect of fitness on glucose, insulin and cortisol responses to diets varying in starch and fat content in Thoroughbred horses with recurrent exertional rhabdomyolysis.

The research focuses on the effect of different diets and fitness levels on blood glucose, insulin, and cortisol levels in Thoroughbred horses suffering from a condition known as Recurrent Exertional Rhabdomyolysis (RER). The study reveals that fit horses fed on high carbohydrate diets show increased post-meal blood glucose, insulin, and cortisol levels, which could potentially trigger their disease condition.

Research Methodology

• The research was conducted on four Thoroughbred mares suffering from RER who underwent a fitness regimen of 10 weeks of treadmill training.
• Three distinct diets were administered to these horses: two high Nonstructural Carbohydrate (NSC) feeds – Sweet Feed (SF) and Processed Pelleted Feed (PL), and a low starch, high fat diet (FAT).
• Each of these diets, providing equal amounts of energy (121 MJ/day), was given in a block pattern for 5 days straight.
• Blood samples were collected before and after feeding as well as at regular intervals of 30-60 minutes for a total duration of 420 minutes post-feeding. The aim was to measure levels of glucose, insulin, and cortisol in the blood.
• After the horses had gone through a detraining period of 3-6 months, they were subjected to the same procedure again to understand the difference in responses due to fitness levels.

Findings of the Research

• The results for the two high NSC diets (SF and PL) were found to be similar.
• Regardless of the type of diet, the cortisol level was higher in fit horses as compared to unfit ones.
• Fit horses fed with SF and PL exhibited higher post-meal insulin levels and insulin to glucose ratios than their unfit counterparts.
• The FAT diet led to lower post-meal glucose and insulin levels compared to SF and PL.
• The higher insulin level in fit horses, noticed while on the SF and PL diets, was absent when these horses were fed the FAT diet.

Conclusion

• The study asserts that high NSC diets but not high fat diets contribute to elevated post-meal glucose, insulin and cortisol levels in fit Thoroughbred horses suffering from RER.
• The combination of these raised levels and the horse’s fitness status may lead to increased excitability, potentially triggering rhabdomyolysis in Thoroughbred horses suffering from RER.