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EQUINES: TEST PROTOCOLS
EQUINE OVERNIGHT DEXAMETHASONE SUPPRESSION TEST
 For the use on horses with suspected hyperadrenocorticism due to an adenoma of the pituitary pars intermedia (PIA). Also used to distinguish between PIA and a typical Cushings (peripheral insulin resistance).
Protocol
  • Collect a basal sample of 2 ml clotted or heparin blood at about 17.00 hrs.
  • Inject 0.04 mg/kg dexamethasone i/m.
  • Collect a further blood sample of clotted or heparin blood 20 hours later.
  • Separate serum/plasma if possible, label samples "basal" and "post dexamethasone".
    • Note
    1. Endogenous ACTH can be measured in conjunction with dexamethasone suppression (special samples handling requirements apply).
    2. Insulin measurement may also be useful.
    Reference
    C.S.L.S Assay Services Information Manual, Edition 1A, p13.

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    GLUCOSE TOLERANCE TEST - EQUINE
     For the investigation of small intestinal absorption in the horse.
    Protocol
  • Fast the horse overnight allowing ad libitum water.
  • Collect a blood sample into a fluoride oxalate (OxF) tube.
  • Administer 1.0g/kg bodyweight of anhydrous glucose (or 1.1g/kg bodyweight glucose monohydrate) by stomach tube as a warm, freshly prepared 20% solution.
  • Collect further OxF blood samples 30, 60, 120 and 180 minutes after dosing.
  • Label the samples "pre", "30 mins", "60 mins", "120 mins" and "180 mins post glucose" and dispatch to the laboratory.
    • Interpretation
    In normal equines, the blood glucose level climbs quickly, peaking at 120 minutes, at around twice the resting value. In small intestinal malabsorption, glucose levels change very little over the test period, producing a "flat curve" when plotted out in the form of a chart.

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    RIG TESTS
    EQUINE
    1. Oestrone Sulphate
    For use in horses and ponies greater than 3 years old.
    Not suitable for use in donkeys.
    Protocol
  • Collect a 2ml sample of clotted or heparin blood.
  • Separate the serum/plasma if possible and dispatch to the laboratory.
    • Note
    1. Approximately 2% of tests produce equivocal results
    2. Both oestrone sulphate and hCG stimulation tests should be performed in animals likely to be the subject of a dispute or legal proceedings.


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    2. hCG STIMULATION TEST
     For use in horses and ponies under three years and donkeys.
    Protocol
  • Collect a basal sample of 2ml clotted or heparin blood.
  • Inject 6000 IU of hCG (Chorulon, Intervet) i/v.
  • Take a second sample of 2ml clotted or heparin blood 30 minutes to 2 hours post hCG injection.
  • Separate the serum/plasma if possible, label "pre" and "post hCG" and dispatch to the laboratory.
    • Note
    1. Approximately 11% of tests produce equivocal results
    2. Both oestrone sulphate and hCG stimulation tests should be performed in animals likely to be the subject of a dispute or legal proceedings.


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