LAUSR

BACKGROUND Identifying intake levels of nonstructural carbohydrates (NSC) that limits 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 non-insulin dysregulated, NID; matched for bodyweight) were randomly fed eight dietary treatments. Dietary treatments were formulated using a base of low-nonstructural carbohydrate pellet (LNSC; 0.04 g of water-soluble carbohydrates (WSC)/kg bwt and 0.01 g 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 (0.03-0.1 g starch/kg bwt). Horses were fed each dietary treatment at a rate of 1 g/kg bwt once over 12-weeks. Serial blood samples were collected pre- and up to 240 minutes 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 > 0.1 g/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 0.1 g/kg bwt/meal, above which significantly increased insulin responses are seen compared to NID horses.