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In-feed Oral Glucose Challenge Test

Resting hyperinsulinaemia is present in approximately 30% of horses with Equine Metabolic Syndrome (EMS). The in-feed oral glucose challenge test offers a more sensitive means of identifying horses with insulin resistance, one of the hallmarks of EMS. Generally, only the post-prandial insulin concentration is interpreted. There is no need to collect a basal serum sample for insulin measurement prior to the oral glucose challenge. Measurement of triglycerides and fasting glucose concentrations may be additional tests alongside characteristic changes in the clinical picture that can be helpful in formulating a diagnosis of EMS. Note however very few horses with EMS exhibit fasting hyperglycaemia.

Species:

Horse

Specimen:

Serum

Container:

Plain (red top) tube

Collection protocol:

  • Fast the horse/pony overnight (12 hours).
  • Give a non-glycaemic feed (eg. chaff) containing 1g/kg bodyweight glucose or dextrose powder mixed with a little water to aid mixing/ingestion.
  • Collect a serum sample two hours after ingestion of the feed for measurement of insulin concentrations.
  • Separate the serum sample from the red cells before sending to the laboratory.

Special handling/shipping requirements:

Serum insulin is unstable at room temperature and must be kept chilled. Send the separated serum samples with gel ice packs to the laboratory as soon as possible. If testing cannot be performed within 24 hours, freeze the separated serum.