Identifying insulinemic responses of ID horses offered varying levels of NSC and meal-sizes

Background: Feeding small meals (∼1 g/kg BW DM basis) providing >10% nonstructural carbohydrates (NSC; starch + water soluble carbohydrate; WSC) has resulted in an augmented insulin response (AIR) in insulin dysregulated (ID) horses, but it's unclear if AIR reflects NSC content or the g NSC/kg BW/meal. Objectives and methods: The insulinemic responses of ID (n = 7) and non-insulin dysregulated (NID; n = 8) horses fed four feeds (A = 6.8% NSC; B = 14.9% NSC; C = 35.5% NSC; D = 44.6% NSC) at three levels of NSC intake (0.06, 0.11-0.12 and 0.17-0.18 g/kg BW) were evaluated in a randomized Latin square design across two phases. Results: ID horses had higher incremental area under the curve (IAUCi; ID: 3223.05±3229.5 vs. NID: 907.2 ± 976.4 IU/mL*minute), 60-minutes post-meal consumption (T60; ID: 43.4 ± 48.8 vs. NID: 12.6 ± 14.6 µIU/ mL) and delta (ID: 20.9 ± 41.7 vs. NID: 6.2 ± 11.4 µIU/mL) insulin for all treatment diets compared to NID horses (p < 0.0001). In Phase 1, ID horse T60 insulin for feedstuff A, was higher with 0.17 compared to 0.06 and 0.11 g NSC/kg BW/meal (p = 0.02); and for B, again, greater for the 0.11 and 0.17 than the 0.06 g NSC/kg BW/meal (p = 0.002). In Phase 2, the T60 insulin of ID horses was higher when given D at 0.18 compared to 0.06 and 0.12 g NSC/kg BW/meal (p = 0.008). Conclusion: Augmented post-prandial insulinemic responses occurred in ID horses fed small meals of pelleted feedstuffs with ≥0.11-0.12 g NSC/kg BW regardless of feed % NSC; however, considerable variation suggests the need for individual monitoring.