Effect of graded inclusion of dietary soybean meal on nutrient digestibility, health, and metabolic indices of adult dogs1

Two studies were conducted using adult dogs to evaluate the effect of increasing the inclusion of soybean meal (SBM) in an adult dog food on body com- position, hematological and biochemical blood analyses, and total tract nutrient digestibility. Nutritionally complete and balanced diets were formulated with commercial- grade SBM (48% CP) to replace 0, 10, 20, or 30% of the protein provided by dried chicken protein resulting in final SBM inclusion of 0, 6.0, 11.5, and 17.0% (as-fed basis), respectively. In study 1, diets were fed during a 24-wk feeding trial using 36 female (spayed), adult hounds to evaluate food intake, BW, body composition, and blood measurements. There were no diet-related differences in food intake or BW. Body composition responded in a quadratic manner to increased dietary SBM inclusion with the percentage (%) of lean mass responding posi- tively (P < 0.05) and absolute amounts of fat mass and percent body fat responding negatively (P < 0.05). All diagnostic blood components remained within normal physiological ranges for healthy, adult dogs. Serum con- centrations of C-reactive protein and IGF-1 were similar among diets. In study 2, diets were evaluated in a digest- ibility study using 12 adult dogs in a 4 × 4 Latin square design. Increased SBM inclusion was associated with lin- ear increases in the digestibility of CP (P < 0.05) and fat (P < 0.05) and CP retention (P < 0.05). Linear reductions in fecal DM content (P < 0.01) and increased fecal output (P < 0.05) were noted with increased SBM inclusion. All diets were similar in DE and ME content, but a quadratic trend was noted with increased SBM inclusion when DE (P = 0.083) and ME (P = 0.062) were expressed per unit of metabolic body size. Overall, it can be inferred from these results that the partial replacement of dried chicken protein with SBM in a nutritionally complete and bal- anced diet does not compromise the nutritional status and long-term health of adult dogs.