251 Effects of red sorghum bran inclusion in extruded diet on apparent total tract digestibility of macronutrients and gross energy, fecal quality, hematology, and serum biochemistry profile of adult dogs.

Abstract Red sorghum bran (RSB), a primary co-product from sorghum milling, is a sustainable ingredient with potential metabolic and gut health benefits due to its high polyphenol concentrations. However, to the authors’ knowledge, the use of RSB as a dietary ingredient for dogs has not been investigated to date. Thus, the objective of this study was to evaluate the effects of dietary RSB intake by healthy adult dogs on apparent total tract digestibility (ATTD) of macronutrients and gross energy, stool quality, hematology, and serum biochemistry profile. Four extruded diets with similar macronutrient composition were formulated with increasing levels of RSB (0, 7, 14, and 28%). The total phenolic content (TPC) in the uncoated diets was analyzed according to standard methods. Twelve adult Beagles [avg. age of 3.97 ± 0.02 yr old and body weight (BW) of 11.15 ± 2.2 kg] were enrolled in a replicated 4 x 4 Latin Square design. In each 28-day period, feces were collected over the last 5 days for ATTD and stool quality assessment, while fasted blood samples were collected on the last day of each period for complete blood counts and serum biochemical analytes. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with diet as fixed effect, and dog and period as random effects. Experimental diets with 14 and 28% RSB had greater TPC concentrations (avg. 3066.3 µg/g) than those with 0 and 7% RSB inclusion (avg. 1971.5 µg/g). No effect (P > 0.05) of diet was observed on BW, food intake, complete blood counts, and biochemical parameters in dogs. Dietary RSB intake linearly decreased (P < 0.05) the ATTD of dry matter, organic matter, protein and gross energy, and had a quadratic (P < 0.05) response for fat ATTD. However, the ATTD coefficients were within acceptable ranges, and the magnitude of change was minimal, aligning with the lack of effect (P > 0.05) of diet on daily fecal output (avg. 40.1 g/day DM basis). Frequency distribution of fecal scores indicated no effect (P > 0.05) of diet on fecal consistency, with scores remaining within ideal range; this is further supported by similar fecal moisture content (avg. 62%) across treatments. The findings of this study suggest that dietary inclusion of RSB up to 28 % slightly lowers the ATTD of macronutrients and gross energy but do not negatively impact stool quality or short-term health in healthy adult dogs. Fecal and plasma metabolite analyses are underway to further evaluate the impact of RSB on metabolism and markers of gut health.