PS4-10. Effects of Different Dietary Dried Corn Distillers Grains Plus Solubles Inclusion Levels on Postprandial Glycemic and Insulinemic Responses in Horses.

Abstract

Evaluation of postprandial glycemic and insulinemic responses is fundamental to assess the metabolic effects of alternative feed ingredients in equine nutrition. Dried corn distillers grains plus solubles (DDGS), a by-product with distinct fermentative and energetic characteristics, requires investigation regarding metabolic safety and potential impacts on glucose-insulin homeostasis. This study aimed to evaluate the effect of increasing dietary DDGS inclusion levels on postprandial glycemic and insulinemic responses in horses. The experiment was conducted at the Research Laboratory of Digestive Health and Equine Performance (LabEqui), School of Veterinary Medicine and Animal Science, University of São Paulo. Eight Arabian geldings were used in a replicated 4 × 4 Latin square design. Daily intake was set at 1.75% of body weight (dry matter basis), consisting of 1.0% forage and 0.75% concentrate (60:40 forage-to-concentrate ratio), according to NRC (2007) recommendations. Water and mineral salt were provided ad libitum. Animals were randomly assigned to one of the four treatments: Control Treatment (CT), with a wheat bran-based concentrate; Treatment 1 (T15), including 15% DDGS; Treatment 2 (T30), including 30% DDGS; and Treatment 3 (T45), including 45% DDGS. Plasma glucose and insulin concentrations were measured before feeding (06:30 AM), 30 minutes after feeding (07:30 AM), and at 60 minutes intervals thereafter (08:30, 09:30, and 10:30 AM). Data were analyzed using linear mixed models (PROC MIXED, SAS), including treatment, time, treatment × time interaction, period as fixed effects, and animal as a random effect. Area under the curve (AUC), maximum concentration (Cmax), and time to peak (Tmax) were calculated. Linear and quadratic polynomial contrasts were applied to assess responses to increasing DDGS inclusion levels. No treatment effects were detected for plasma glucose or insulin concentrations at any sampling time (P > 0.05). Glucose AUC ranged from 1,309 to 1,379 [mmol/L]×min and Cmax from 112 to 119 mg/dL. Insulin AUC ranged from 0,014 to 0,019 [IU/L]×min and Cmax from 92.01 to 144.36 µIU/mL, with no differences among treatments (P > 0.05). No linear or quadratic effects of DDGS inclusion were observed. Plasma concentrations followed a typical postprandial pattern, with an increase after feeding and subsequent gradual decline. Similarly, AUC, Cmax, and Tmax did not differ among treatments, indicating comparable total exposure, peak magnitude, and response kinetics across diets. In conclusion, dietary inclusion of up to 45% DDGS did not alter postprandial glycemic or insulinemic responses in horses, indicating maintenance of glucose-insulin homeostasis and metabolic safety under the evaluated conditions.