title: 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.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Ten healthy adult horses.
  
  
  METHODS
  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
  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.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN.
authors.forename: F R
authors.initials: FR
authors.lastname: Bertin
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN.
authors.forename: S D
authors.initials: SD
authors.lastname: Taylor
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN.
authors.forename: A W
authors.initials: AW
authors.lastname: Bianco
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN. sojkaje@purdue.edu.
authors.forename: J E
authors.initials: JE
authors.lastname: Sojka-Kritchevsky
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects*; D005508:Food Deprivation / Q000502:physiology*; D005951:Glucose Tolerance Test / Q000662:veterinary*; D006736:Horses / Q000097:blood* / Q000378:metabolism*; D007328:Insulin / Q000097:blood* / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D007328:Insulin
keywords: Clinical pathology; Endocrinology; Equine; Glucose metabolism