Effect of maltodextrin supplementation on blood glucose, lactate, insulin, and cortisol levels of horses subjected to submaximal incremental exercise test

Paulo Moreira Bogossian,Ayrton Rodrigo Hilgert,Guilherme De La Penha Chiacchio Fernandes,Maria Letícia Tescaro Piffer,Talissa Rezende Martins,Dayane Amorim De Oliveira Araujo,Wilson Roberto Fernandes,Pedro Vicente Michelotto Junior,Fernanda Barros Maschietto,Tiago Marcelo Oliveira

doi:10.7213/1981-4178.2019.17005

Abstract

Riders and trainers believe that oral maltodextrin (MD) supplementation prior to exercise increases blood glucose availability and delay the onset of fatigue in horses, although there is no evidence supporting this claim. Therefore, we aimed to evaluate the effect of MD supplementation on blood glucose, L-lactate, insulin, and cortisol levels and heart rate in horses subjected to an incremental exercise test. A randomized placebo-controlled crossover trial was designed to test the effect of three doses of MD (50 g, 100 g and 200 g) on blood glucose, L-lactate, insulin, and cortisol levels and heart rate of four Purebred Lusitanian geldings. A seven-step incremental field exercise test was used; the initial speed was set at 2.5 m/s, followed by 3.3 m/s, 4.1 m/s, 5.0 m/s, 6.6 m/s, and 8.4 m/s. There was a significant influence of exercise itself on plasma glucose and L-lactate concentrations and on heart rate (p < 0.05), whereas the amount of MD administered changed only the cortisol levels (p < 0.05). During rest and exercise, the variables remained within the normal reference range for stalled and exercising horses, respectively. Blood glucose levels in the placebo group at rest, 5.0 m/s, and 8.4 m/s were 87.63 ± 3.25 mg/dL, 78.33±10.08 mg/dL, and 95.18 ± 14.73 mg/dL, respectively, whereas those for the group supplemented with 200 g MD were 99.25±12.19 mg/dL, 79.55±13.81 mg/dL, and 97.30 ± 16.46 mg/dL, respectively. The mean cortisol levels in the placebo and 200 g MD groups at 8.4 m/s were 1.20 ± 0.53 mmol/L and 5.54 ± 4.73 mmol/L, respectively. In conclusion, MD supplementation increased serum cortisol levels and showed no effect on heart rate, blood glucose, L-lactate and serum insulin levels of horses submitted to an incremental exercise test.

Highlights

Oral carbohydrate (CHO) supplementation is a nutritional strategy widely adopted across many equestrian disciplines
Blood L-lactate, serum insulin, serum cortisol, and heart rate were within the reference range at rest, and there were no differences among groups
Blood L-lactate, serum insulin levels, and the heart rate did not differ among groups during the exercise test; the serum cortisol concentrations of the supplemented groups (50, 100 and 200 g) were higher than placebo group (0 g) (p < 0,01) (Figure 1 and Table 1)

Summary

Introduction

Oral carbohydrate (CHO) supplementation is a nutritional strategy widely adopted across many equestrian disciplines. Trainers and riders believe that increased blood glucose availability leads to enhanced endurance performance, and rapid post-exercise recovery. This belief is probably an erroneous extrapolation from the study of Farris et al (1995), who showed that intravenous glucose infusion increased blood glucose availability and delayed the onset of fatigue in horses during submaximal exercise on a treadmill. Oral supplementation with combined glucose and fructose effectively increased glucose availability during low-intensity exercise in horses (Bullimore et al, 2000). MD supplementation prior and during biathlons was shown to prevent exercise-induced hypoglycemia, without increasing blood insulin and cortisol levels (Mamus et al, 2006)

Objectives

Methods

Results