Moderate Dietary Carbohydrate Improves Glucose Tolerance and High Dietary Fat Impairs Glucose Tolerance in Aged Thoroughbred Geldings

In aged non-obese geldings, a moderate intake of non-structural carbohydrate (31% of digestible energy) improved glucose tolerance, and high dietary fat (30% of digestible energy) impaired glucose tolerance during intravenous glucose tolerance test compared with an all-hay diet. Moderate carbohydrate equates to 2.0 to 2.5 kg of grain per day for a 500-kg horse. Authors’ address: Kentucky Equine Research, 3910 Delaney Ferry Rd, Versailles, KY 40383; e-mail: [email protected].

1. Introduction

Low-carbohydrate diets are often recommended for horses with metabolic syndrome, and high-fat diets are useful for treating horses with recurrent exertional rhabdomyolysis and polysaccharide storage myopathy. It is questionable whether these types of diets are appropriate for normal, non-obese horses. This study was conducted to determine whether a moderate daily intake of carbohydrate from oats or a high level of fat intake from vegetable oil would affect glucose tolerance as measured by an intravenous glucose tolerance test (IVGTT).

2. Materials and Methods

Four aged Thoroughbred geldings were used in a 4 x 4 Latin square design study. The treatments were isocaloric and consisted of ~11 Mcal digestible energy (DE)/d from grass hay and ~ 7.5 Mcal DE/d from either (1) additional grass hay (GRASS53% DE fiber, 17% DE non-structural carbohydrate [NSC]), (2) alfalfa pellets (ALF-54% DE fiber, 15% DE NSC), (3) oats (OATS-31% DE NSC), or (4) alfalfa cubes + soybean oil (OIL-30% DE fat). 

3. Results and Discussion

A moderate intake of carbohydrate improved glucose clearance during IVGTT compared with an all-hay diet or a high-fat diet. Blood glucose returned to baseline in 126.6 ± 25.8 minutes in OATS compared with 216.7 ± 23.5 minutes in OIL (p < 0.05).