Identifying possible thresholds for nonstructural carbohydrates in the insulin dysregulated horse.
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BACKGROUND: Identifying intake levels of nonstructural carbohydrates (NSCs) that limit the postprandial insulinaemic response in the insulin dysregulated (ID) horse may help reduce hyperinsulinaemia-associated laminitis (HAL) risk. OBJECTIVE: To determine if ID horses have thresholds for pure sources of starch and sugar, above which there is an augmented insulin response. STUDY DESIGN: Randomised crossover experiment. METHODS: Fourteen adult horses (6 ID and 8 noninsulin dysregulated, NID; matched for bodyweight) were randomly fed eight dietary treatments. Dietary treatments were formulated using a base of low-nonstructural carbohydrate pellet (LNSC; 0.04g of water-soluble carbohydrates (WSCs)/kg bwt and 0.01g of starch/kg bwt), to which pure sugar (dextrose) or starch (50:50 mix of waxy-maize and oat starch powder) sources were titrated to create diets with increasing amounts of either WSC (0.06-0.17g WSC/kg bwt), or starch (0.03-0.1g starch/kg bwt). Horses were fed each dietary treatment at a rate of 1g/kg bwt once over 12weeks. Serial blood samples were collected pre- and up to 240min postprandially. Insulin was determined via RIA and diet analytes were determined via wet chemistry. Statistical analysis was performed with a mixed effect model. Positive incremental area under the curve for insulin (IAUCi) was calculated for all horses and dietary treatments. RESULTS: There was no significant effect of diet in NID horses but diets with NSC>0.1g/kg bwt produced an augmented response in ID horses compared with the LNSC (p<0.05). ID horses IAUCi were also significantly different to all NID IAUCi for diets with NSC>0.1g/kg (p<0.04). Apparent thresholds for sugar and starch addition varied. CONCLUSIONS: Based on this study, using supplemental pure starch and sugar sources, ID horses seem to have an apparent threshold for NSC of around 0.1g/kg bwt/meal, above which significantly increased insulin responses are seen compared with NID horses.
