Abstract: Background: Dietary management is the most important treatment for equine insulin dysregulation (ID) and often involves feeding low non-structural carbohydrate (NSC), high-protein ration balancers and grass hay. Data suggest that post-prandial hyperinsulinemia can be exacerbated by a high-protein meal in patients with ID, creating concern about the safety of this nutritional intervention.
Hypothesis: Consumption of a low-NSC, high-protein meal will induce post-prandial hyperinsulinemia, which will be amplified after induction of ID in horses.
Animals: Seven adult, light-breed horses with normal endogenous [ACTH].
Methods: Each horse underwent a frequently-sampled insulin-modified IV glucose tolerance test to characterize systemic insulin and glucose dynamics, followed by a feed challenge test (1 kg ration balancer [min 32% crude protein, max 13% NSC] consumed within 15 minutes, with [insulin] and [glucose] measured at baseline and every 30 minutes for 240 minutes after the meal). Both tests were repeated after induction of ID (dexamethasone 0.08 mg/kg PO once daily for 7 days). Outcomes were compared between baseline and ID conditions.
Results: ID was associated with exacerbation of post-prandial hyperinsulinemia and hyperglycemia after high-protein meal feeding. ID AUCins (548.9 ± 150 µIU/mL×min) was significantly higher than baseline AUCins (216.2 ± 104.4 µIU/mL×min; P = 0.003). ID AUCgluc (89.5 [60−115] mg/dL×min) was significantly higher than baseline AUCgluc (75 [34.9−94] mg/dL×min; P = 0.03).
Conclusions and Clinical Importance: Horses with experimentally-induced ID displayed significantly higher glycemic and insulinemic responses to a high-protein meal than at baseline, suggesting that high-protein ration balancers may complicate nutritional management of equine ID.
