Diagnosis of insulin dysregulation in adult horses is frequently performed using Karo Light corn syrup. However, Karo Light syrup is not readily available worldwide. Composition of available corn syrups may vary, leading to different insulin and glucose results. In this study, we evaluated agreement between two formulations of corn syrup, Karo Light and Crown Lily White. This study consisted of two experiments. In experiment 1, 14 horses were allowed access to hay or pasture prior to the OST. In experiment 2, 10 horses were fasted overnight prior to the OST. For both studies, corn syrup formulation order was randomized and oral sugar tests were performed one week apart. Blood was drawn for measurement of blood glucose and insulin concentrations at T0 (prior to administration of corn syrup) and 30, 60, 75, 90, and 120 minutes after administration of corn syrup. Blood glucose was measured using a handheld glucometer and serum insulin was measured using a radioimmunoassay. Data was analyzed for normality. Insulin concentrations were log transformed for normality. Changes in glucose and insulin concentration at each time point, area under the curve (AUC), maximum concentration (Cmax), and time at Cmax (Tmax) were compared between formulations using a two way analysis of variance with repeated measures. Bland Altman analysis was used to determine agreement in insulin concentrations between formulations. There were no significant differences between Karo and Crown syrup formulations at any individual time points for insulin or glucose concentrations in either experiment (P > 0.2) There were no significant differences between the area under the curve, Tmax, or Cmax for insulin or glucose concentrations with Karo compared to Crown syrup (P > 0.1). Bland-Altman analysis of insulin concentrations indicated a mean bias (Karo-Crown) of 4 µIU/mL (95% limits of agreement, -11.7 to 19.6 µIU/mL; experiment 1) or a mean bias of 1.6 µIU/ml (95% limits of agreement, -11 to 14.2 µIU/ml; experiment 2) for insulin concentrations at 75 minutes. This study suggests that horses have similar glucose and insulin responses to these two formulations of corn syrup.
University of Calgary
Thursday, June 14
3:15 PM – 3:30 PM
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