Soybean Hulls in Equine Feed Concentrates: Apparent Nutrient Digestibility, Physicochemical and Microbial Characteristics of Equine Feces

• Total tract digestibility was unaffected by inclusion of soybean hulls in concentrate
• Fecal parameters were unaffected by inclusion of soybean hulls
• Streptococcus spp. and Lactobacillus spp. were unaffected by the experimental diets
• Diets with up to 28% soybean hulls in the concentrate can be used as equine feed
• Soybean hulls are a safe ingredient for equine feed concentrate.

The aim of this study was to evaluate the soybean hulls inclusion in concentrates for horses as an alternative fiber source, through the apparent digestibility of nutrients and physicochemical characteristics of the feces. Five mares (3.5 ± 0.8 year old; 492.5 ± 44.5 kg) were used in a 5 × 5 Latin square design. Experimental diets were formulated for animals at maintenance and were composed of 60% energy from forage (Coastcross hay) and 40% from a concentrate, with increasing levels of soybean hulls (0, 7, 14, 21, and 28%). The inclusion of soybean hulls at any level in the concentrate had no effect (P > .05) on the following parameters: apparent digestibility coefficients of nutrients in the diet; feces pH, buffering capacity (BC) to pH 5 (BC 5) and to pH 6 (BC six), and ratios of short-chain fatty acids (SCFAs) as well as Streptococcus spp. and Lactobacillus spp. Diets with up to 28% soybean hulls in the concentrate can be used as equine feed without negatively affecting digestibility, the SCFAs concentrations or selected microbiota, and physicochemical characteristics in the feces.