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Randomized Controlled Trial
. 2016 Sep;30(5):1726-1731.
doi: 10.1111/jvim.14529. Epub 2016 Aug 2.

The Effect of Fasting Duration on Baseline Blood Glucose Concentration, Blood Insulin Concentration, Glucose/Insulin Ratio, Oral Sugar Test, and Insulin Response Test Results in Horses

F R Bertin  1 , S D Taylor  1 , A W Bianco  1 , J E Sojka-Kritchevsky  2
Affiliations
Randomized Controlled Trial

The Effect of Fasting Duration on Baseline Blood Glucose Concentration, Blood Insulin Concentration, Glucose/Insulin Ratio, Oral Sugar Test, and Insulin Response Test Results in Horses

F R Bertin et al. J Vet Intern Med. 2016 Sep.

Abstract

Objectives: Published descriptions of the oral sugar test (OST) and insulin response test (IRT) have been inconsistent when specifying the protocol for fasting horses before testing. The purpose of our study was to examine the effect of fasting duration on blood glucose concentration, blood insulin concentration, glucose/insulin ratio, OST, and IRT results in horses.

Animals: Ten healthy adult horses.

Procedures: Both OST and IRT were performed on horses without fasting and after fasting for 3, 6, and 12 hours. Thus, 8 tests were performed per horse in a randomized order. Blood collected at the initial time point of the OST was analysed for both blood glucose and serum insulin concentrations so that baseline concentrations and the glucose/insulin ratio could be determined. Unless fasted, horses had free-choice access to grass hay.

Results: There was no effect of fasting and fasting duration on blood glucose concentration, serum insulin concentration, glucose/insulin ratio, or the OST. Response to insulin in the IRT was decreased in fasted horses. The effect increased with fasting duration, with the least response to insulin administration after a 12-hour fast.

Conclusions and clinical relevance: These data indicate that insulin sensitivity is not a fixed trait in horses. Fasting a horse is not recommended for a glucose/insulin ratio or IRT, and fasting a horse for 3 hours is recommended for the OST.

Keywords: Clinical pathology; Endocrinology; Equine; Glucose metabolism.

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Figures

Figure 1
Figure 1
Serum insulin concentration (mean ± standard deviation, μIU/mL) before and 60 and 90 minutes after oral administration of 15 mL/100 kg of concentrated corn syrup in 10 horses after not fasting (open circles) and fasting for 3 (black squares), 6 (open triangles), and 12 (black stars) hours (*P < .05 from baseline).
Figure 2
Figure 2
Effect of fasting on values of serum glucose concentration (mean ± standard deviation, mg/dL) after intravenous administration of 0.1 IU/kg regular insulin in 10 horses after not fasting (open circles) and fasting for 3 (black squares), 6 (open triangles), and 12 (black stars) hours (*P < .05 from baseline).
See this image and copyright information in PMC

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