Effect of diet on Thoroughbred horses with recurrent exertional rhabdomyolysis performing a standardised exercise test

Abstract

Summary Previous studies have associated recurrent exertional rhabdomyolysis (RER) with a diet high in soluble carbohydrate (CHO). The purpose of this study was to investigate the effect of 3 diets on clinical and metabolic parameters in 5 Thoroughbred horses with RER and 3 healthy Thoroughbreds performing a standardised exercise test (SET). Two diets were formulated to meet energy requirements for the amount of exercise being performed in the form of CHO or fat (21.4 Meal DE/day). The third diet was formulated to provide 135% of the DE of the other 2 diets in the form of an excessive amount of carbohydrate (28.8 Meal DE/day). Diets were fed in a crossover design for 3 week blocks and then horses performed a near maximal SET. Changes in heart rate (HR), plasma lactate, plasma glucose, total plasma solids, packed cell volume (PCV), muscle lactate and muscle glycogen concentration were measured immediately prior to, during, and 5 min after exercise. Serum creatine kinase (CK) activity was measured prior to and 4 h post SET. A 2‐way ANOVA was used to examine the effect of group and dietary treatment. When dietary treatments were compared, horses fed the high‐CHO diet had a mean pre‐SET PCV and pre‐SET HR that was higher than horses fed the fat diet (P=0.06 and P=0.07, respectively). Pre‐SET heart rates were highest in RER horses consuming the high‐CHO diet compared to RER horses consuming the low‐CHO and fat diets (P = 0.02). Horses with RER had 4 h post SET CK activity greater than 400 u/l in 7/14 (50%) measurements compared to control horses which had CK activity greater than 400 u/l in 2/7 (29%) measurements. This study did not demonstrate a significant effect of diet on rhabdomyolysis, indicated by CK activity, or on the metabolic response to exercise. However, diet may have a calming effect on Thoroughbred horses with RER as manifested by decreased pre‐exercise heart rates and decreased pre‐exercise PCV in horses fed the fat diet.

Effects on exercise metabolism of varying dietary starch and sugar proportions

“…The reason for an increased heart rate and/or increased excitability after carbohydrate consumption in horses is not known. MacLeay et al (1999) showed that horses tended to have a higher HR and PCV prior to an exercise test when fed a diet exceeding their energy requirements due to carbohydrate supplementation, compared to when they were fed a fat diet according to their requirements. In addition, in the same study, horses with a history of exertional rhabdomyolysis had significantly higher HRs when fed the excessive diet compared to when fed diets equalling their needs (carbohydrate diet and fat diet).…”

Applied Animal Nutrition

“…• Overfeeding of carbohydrates (MacLeay et al 1999) • Electrolyte or mineral imbalances, especially with potassium (Harris 1991) • Deficiency of selenium and/or Vitamin E If elite-level performance is to be maintained in horses predisposed to these muscle problems it is crucial to reduce the amount of carbohydrate in the diet as much as possible. This is done by increasing the use of non-starch energy sources such as fibre and oil.…”

Effects of fat supplementation on plasma glucose, insulin and fatty acid analysis in ponies maintained on a forage‐based diet

“…Performance horses are traditionally fed a starch‐rich, concentrate‐based diet due to the energy requirements for the activities performed in the sport. Nevertheless, this type of diet has been reported to negatively impact the health (Goncalves, Julliand, & Leblond, ; Tinker et al., ; Luthersson, Hou Nielson, Harris, & Parkin, ; MacLeay et al., ) and behaviour (Gillham, Dodman, Shuster, Kream, & Rand, ; Kusunose, ; Redbo, Redbo‐Torstensson, Odberg, Hedendahl, & Holm, ) in the horse, and so, researchers have investigated whether a high‐energy forage‐based diet is detrimental to the performance of the equine athlete (Connysson, Essen‐Gustavsson, Lindberg, & Jansson, ; Connysson et al., ; Essen‐Gustavsson, Connysson, & Jansson, ; Ringmark, Roepstorff, Hedenstrom, Lindholm, & Jansson, ). High‐energy forage‐based diet was reported to be a suitable alternative to a grain‐rich diet in performance horses with benefits documented in the recovery of muscle (Essen‐Gustavsson et al., ) and fluid balance (Connysson et al., ) in the exercising horse along with the overall performance (Ringmark et al., ).…”