Effect of fitness on glucose, insulin and cortisol responses to diets varying in starch and fat content in Thoroughbred horses with recurrent exertional rhabdomyolysis
Article first published online: 8 NOV 2010
© 2010 EVJ Ltd
Equine Veterinary Journal
Special Issue: Proceedings of the 8th International Conference on Equine Exercise Physiology
Volume 42, Issue Supplement s38, pages 323–328, November 2010
How to Cite
FINNO, C. J., McKENZIE, E., VALBERG, S. J. and PAGAN, J. (2010), Effect of fitness on glucose, insulin and cortisol responses to diets varying in starch and fat content in Thoroughbred horses with recurrent exertional rhabdomyolysis. Equine Veterinary Journal, 42: 323–328. doi: 10.1111/j.2042-3306.2010.00199.x
- Issue published online: 8 NOV 2010
- Article first published online: 8 NOV 2010
- [Paper received for publication 09.01.10; Accepted 11.06.10]
Reasons for performing study: Recurrent exertional rhabdomyolysis (RER) occurs in fit, nervous Thoroughbreds fed high nonstructural carbohydrate (NSC) diets. Clinical signs are diminished by feeding low NSC, high fat diets; however, the mechanism is unclear.
Objective: To determine if the glucose, insulin and cortisol response to isocaloric diets varying in fat and NSC availability differ in fit vs. unfit Thoroughbreds with RER.
Materials and methods: Four fit (10 weeks treadmill training) RER Thoroughbred mares were exercised and fed 3 isocaloric (121 MJ/day) diets in a 5 day/diet block design. Two high NSC concentrates, sweet feed (SF) and a processed pelleted feed (PL) and a low starch high fat feed (FAT) were used. After 24 h of rest and a 12 h fast, horses ate half their daily concentrate. Blood sampled for [glucose], [insulin] and [cortisol] was obtained before, immediately after and at 30–60 min intervals for 420 min. After 3–6 months detraining period, the block design was repeated.
Results: Results for SF and PL were similar. Regardless of diet, cortisol was higher in fit vs. unfit horses. Fit horses on SF/PL had higher post prandial [insulin] and insulin:glucose ratio than unfit horses. FAT resulted in lower post prandial [glucose] and [insulin] vs. SF/PL. Higher [insulin] in fit vs. unfit horses was not seen on the FAT diet.
Conclusions: Increased post prandial [glucose], [insulin] and [cortisol] induced by high NSC, but not high fat, feeds are enhanced by fitness in RER horses. This combination may trigger rhabdomyolysis through increased excitability in RER Thoroughbreds.