BackgroundSeveral tests have been evaluated in horses for quantifying insulin dysregulation to support a diagnosis of equine metabolic syndrome. Comparing the performance of these tests in the same horses will provide clarification of their accuracy in the diagnosis of equine insulin dysregulation.ObjectivesThe aim of this study was to evaluate the agreement between basal serum insulin concentrations (BIC), the oral sugar test (OST), the combined glucose‐insulin test (CGIT), and the frequently sampled insulin‐modified intravenous glucose tolerance test (FSIGTT).AnimalsTwelve healthy, light‐breed horses.MethodsRandomized, prospective study. Each of the above tests was performed on 12 horses.ResultsMinimal model analysis of the FSIGTT was considered the reference standard and classified 7 horses as insulin resistant (IR) and 5 as insulin sensitive (IS). In contrast, BIC and OST assessment using conventional cut‐off values classified all horses as IS. Kappa coefficients, measuring agreement among BIC, OST, CGIT, and FSIGTT were poor to fair. Sensitivity of the CGIT (positive phase duration of the glucose curve >45 minutes) was 85.7% and specificity was 40%, whereas CGIT ([insulin]45 >100 μIU/mL) sensitivity and specificity were 28.5% and 100%, respectively. Area under the glucose curve (AUC g0‐120) was significantly correlated among the OST, CGIT, and FSIGTT, but Bland–Altman method and Lin's concordance coefficient showed a lack of agreement.ConclusionsCurrent criteria for diagnosis of insulin resistance using BIC and the OST are highly specific but lack sensitivity. The CGIT displayed better sensitivity and specificity, but modifications may be necessary to improve agreement with minimal model analysis.

BackgroundThe enteroinsular axis (EIA) comprises intestinal factors (incretins) that stimulate insulin release after PO ingestion of nutrients. Glucose‐dependent insulinotropic polypeptide (GIP) and glucagon‐like peptide‐1 (GLP‐1) are the main incretins. The EIA has not been investigated in healthy neonatal foals but should be important because energy demands are high in healthy foals and dysregulation is frequent in sick foals.Objectives and HypothesisTo evaluate the EIA response to carbohydrates or fasting in newborn foals. We hypothesized that incretin secretion would be higher after PO versus IV carbohydrate administration or fasting.AnimalsThirty‐six healthy Standardbred foals ≤4 days of age.MethodsProspective study. Blood was collected before and after a PO glucose test (OGT; 300, 500, 1000 mg/kg), an IV glucose test (IVGT; 300, 500, 1000 mg/kg), a PO lactose test (OLT; 1000 mg/kg), and fasting. Foals were muzzled for 240 minutes. Blood was collected over 210 minutes glucose, insulin, GIP, and GLP‐1 concentrations were measured.ResultsOnly PO lactose caused a significant increase in blood glucose concentration (P < .05). All IV glucose doses induced hyperglycemia and hyperinsulinemia. Concentrations of GIP and GLP‐1 decreased until foals nursed (P < .05), at which time rapid increases in glucose, insulin, GIP, and GLP‐1 concentrations occurred (P < .05).Conclusions and Clinical ImportanceHealthy newborn foals have a functional EIA that is more responsive to milk and lactose than glucose. Non‐carbohydrate factors in mare's milk may be important for EIA activity. Constant exposure of intestinal cells to nutrients to maintain EIA activity could be relevant to management of sick foals. Foals can be fasted for 4 hours without experiencing hypoglycemia.

BackgroundCobalt chloride (CoCl2) is administered to racehorses to enhance performance. The purpose of this study was to evaluate the clinical, cardiovascular, and endocrine effects of parenterally administered CoCl2.ObjectivesTo describe the effects of weekly intravenous doses of CoCl2 on Standardbred horses.AnimalsFive, healthy Standardbred mares.MethodsProspective, randomized, experimental dose‐escalation pilot. Five Standardbred mares were assigned to receive 1 of 5 doses of CoCl2 (4, 2, 1, 0.5, or 0.25 mg/kg) weekly IV for 5 weeks. Physical examination, blood pressure, cardiac output, and electrocardiography (ECG) were evaluated for 4 hours after administration of the first and fifth doses. Blood and urine samples were collected for evaluation of cobalt concentration, CBC and clinical chemistry, and hormone concentrations.ResultsAll mares displayed pawing, nostril flaring, muscle tremors, and straining after CoCl2 infusion. Mares receiving 4, 2, or 1 mg/kg doses developed tachycardia after dosing (HR 60–126 bpm). Ventricular tachycardia was noted for 10 minutes after administration of the 4 mg/kg dose. Increases in systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and mean arterial pressure (MAP) occurred after administration of all doses (4, 2, 1, 0.5, and 0.25 mg/kg). Profound hypertension was observed after the 4 mg/kg dose (SAP/DAP, MAP [mmHg] = 291–300/163–213, 218–279). Hemodynamics normalized by 1–2 hours after administration. ACTH and cortisol concentrations increased within 30 minutes of administration of all CoCl2 doses, and cardiac troponin I concentration increased after administration of the 4 and 2 mg/kg doses.Conclusions and Clinical ImportanceThe degree of hypertension and arrhythmia observed after IV CoCl2 administration raises animal welfare and human safety concerns.

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