Evaluation of soyabean meal as a protein source in canine foods

Eight adult female dogs (18.2 ± 0.4 kg) were used in an experiment to determine the feeding value of soyabean meal (SBM) in a complete food fed to dogs. All foods contained graded concentrations of SBM (151-461 g/kg dry matter (DM)) resulting in foods that were 100, 150, 200 and 250 g/kg crude protein (CP). Daily dry matter intake averaged 296 ± 10 g per day. An increase in SBM resulted in a decrease in fecal moisture from 389 to 265 g/kg (linear; P < 0.001) and fecal DM output increased from 49.8 to 131.4 g per day (linear; P < 0.001). Ileal DM flow increased from 56.6 to 200.7 g per day (linear; P < 0.001). Small intestinal DM digestibility decreased from 0.81 to 0.34 (linear; P < 0.001) and total tract DM digestibility decreased from 0.83 to 0.57 (linear; P < 0.001) as SBM increased. Large intestinal DM digestibility increased from 0.12 to 0.34 with increasing SBM (linear; P < 0.001). Crude protein fecal excretion increased from 10.0 to 27.5 g per day (linear; P < 0.001) and ileal flow of CP increased from 10.6 to 38.1 g per day (linear; P < 0.001) as SBM increased. Small intestinal CP digestibility decreased from 0.65 to 0.51 (linear; P < 0.002) with increasing SBM. Large intestinal CP digestibility increased from 0.05 to 0.27 (linear; P < 0.021) with increasing SBM. Total tract CP digestibility was unaffected by treatment (P < 0.267) as SBM increased. Disappearance of all amino acids (AA) (g per day), with the exception of cysteine and tryptophan, increased (linear; P < 0.001) with increasing SBM. Glutamate had the highest disappearance ranging from 4.98 to 10.89 g per day. Tryptophan and cysteine had the lowest disappearance ranging from 0.35 to 0.43 g per day and 0.29 to 0.36 g per day, respectively. Arginine had the highest overall digestibility ranging from 0.85 to 0.88 whereas, threonine and cysteine had the lowest digestibility ranging from 0.39 to 0.57 and 0.30 to 0.60, respectively. These data indicate that SBM can adversely affect the digestibility of canine foods in concentrations greater than 150 g/kg of the food.