Texas Equine Veterinary Association

www.texasequineva.com • 19 Oral sugar test (OST) is an easy dynamic test that has greater sensitivity than the basal insulin test. The test measures the postprandial insulin response. • Fast for three to six hours prior to testing • Collect blood at baseline for insulin and glucose o Measuring glucose concentrations will help to detect diabetes mellitus (very rare) • Administer 0.15 mL/kg or 0.45 mL/kg corn syrup (i.e. Karo light corn syrup) via syringe o The 0.45 mL/kg dose increases test performance but caution should be used when testing horses that are suspected to be severely insulin dysregulated • Collect blood at 60 and/or 90 minutes for insulin and glucose Check with the laboratory for reference values and type of blood sample (i.e. EDTA or serum) Insulin tolerance test (ITT) is another dynamic test that measures insulin tissue sensitivity by evaluating the glucose response to exogenous insulin. The test does carry the risk of hypoglycemia. • Do not fast—perform in pasture or hay fed state • Collect blood at baseline for insulin • Administer 0.10 IU/kg regular insulin intravenously • Collect blood at 30 minutes for glucose • Feed meal immediately after sample collection Check with the laboratory for reference values and type of blood sample (i.e. EDTA or serum) Other dynamic testing options are available such as the in- feed oral glucose tolerance test and the combined glucose insulin test. In addition, evaluation of leptin, triglyceride, and/or adiponectin concentrations have been used to aid in the diagnosis of EMS. The reader is directed to the references for additional information on these tests. 3 There are multiple approaches to diagnosing EMS and one may get different recommendations depending on the source. Some of the available laboratories for endocrine testing include Animal Health Diagnostic Center at Cornell University (https://ahdc.vet.cornell.edu/) and Michigan State Veterinary Diagnostic Laboratory (https://cvm.msu.edu/vdl). Equine ACTH and insulin are no longer performed at TVMDL. Testing can be helpful in determining the state of ID and in monitoring response to treatment and management. Nonetheless, if testing is not possible, it may be appropriate to make diet and exercise recommendations without a definitive diagnosis if the horse is overweight and showing signs of chronic or acute laminitis. TREATMENT/MANAGEMENT (Figure 3) – Nutritional management is of utmost importance when addressing a horse with EMS and specific dietary recommendations are dependent upon the condition of the horse. 1,3 For obese horses (BCS 6-9/9), the initial diet should eliminate or severely restrict grazing and NO grain should be fed. Grass hay with low NSC content should be fed at 1.5% current body weight on an as-fed basis daily. Body weight should be reassessed 30 days after the diet is initiated. If the horse is resistant to weight loss than the amount fed should be gradually reduced to 1.2% body weight on an as-fed basis. Figure 2 – A closer look at the fore feet of the mare in Figure 1. ere is evidence of abnormal hoof confirmation including dishing of the dorsal surface of the hoof and divergent hoof rings (arrows). Radiographs revealed evidence of chronic laminitis. (Photo credit of Piper Norton)

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