Digestibility of Nutrients and Digestive Health in Horses Submitted to Moderate Exercise and Supplemented With Diets Formulated With Soybean Hulls

Soybean hulls (SHs) are a feedstuff that has been widely studied as an alternative ingredient in horse diets because of its fermentable carbohydrates with low glycemic index. The objective was to assess the influence of the inclusion of SH, in substitution for 0%, 10%, 20%, 30%, and 40% of the concentrate (kg/kg), on the apparent digestibility of nutrients, fecal pH and score, and the postprandial glycemic responses of five geldings submitted to moderate-intensity exercise. The study lasted 50 days, divided into five 10-day periods of 7 days for diet adaptation and 3 days for total feces collection. For the glycemic tests, blood was collected 30 minutes before and 30, 60, 90, 120, 180, 240, and 300 minutes after the administration of SH. Data were submitted to analyses of variance in a Latin square (5 × 5) design, and means were compared by the Tukey test at 5% of significance. There were no effects of treatments on the apparent digestibility of nutrients (P > .05), except for acid detergent fiber and hydrolyzable carbohydrate in 30% and 40% SH diets, and on slowly fermented carbohydrate in the 40% SH diet. Fecal parameters, glucose levels, and peak were not influenced (P > .05) by the increasing levels of SH in the diet. The use of SHs replacing up to 40% of the concentrate supplementation in a diet (kg/kg) improved the digestibility of fermentable carbohydrates and did not impair glycemia of horses under moderate-intensity exercise.