Effects of the inclusion of carbohydrases and different soybean meals in the diet on palatability, digestibility and faecal characteristics in dogs

The objectives of this study were to evaluate the palatability, coefficient of total tract apparent digestibility (CTTAD), metabolisable energy (ME) and faecal characteristics of dogs fed diets with increasing levels of soybean meals (SBM) with or without the inclusion of an enzyme complex with α-galactosidase, β-glucanase, and xylanase activity. Iso-proteic diets containing 0, 150 or 300 g of regular SBM (RSBM)/kg, corresponding to 460 g of crude protein (CP)/kg, or high-protein SBM (HSBM), corresponding to 500 g CP/kg, with or without 2.0 g enzymes/kg, were evaluated in three experiments. In experiment 1, a palatability test was performed to make six pair-wise comparisons: 0 vs. 150 g RSBM/kg; 0 vs. 300 g RSBM/kg; 300 g RSBM vs. 300 g HSBM/kg; 0 vs. 0 g RSBM/kg + enzymes; 300 g RSBM vs. 300 g RSBM/kg + enzymes and 300 g HSBM vs. 300 g HSBM/kg + enzymes. In addition, two digestibility trials were conducted to evaluate three levels of RSBM (experiment 2) or HSBM (experiment 3) diets. The results of experiment 1 indicated that dogs preferred diets containing 300 g HSBM/kg to the RSBM diet (P<0.05), whereas they preferred RSBM diets relative to the control diet (P<0.05). Dogs also preferred the control and RSBM diets with enzymes to the diets without enzymes (P<0.05). In experiments 2 and 3, enzyme supplementation increased the CTTAD of dry matter (DM), organic matter and CP of the RSBM and HSBM diets (P<0.05). The RSBM×enzymes interaction supplied 0.53 MJ/kg in addition to the ME in the 150 g RSBM/kg + enzymes diet, relative to the control diet (P<0.05). The inclusion of RSBM and HSBM in the diet increased the CTTAD of the DM and CP compared to the control diet but reduced that of ether extract and ME (P<0.05). The faecal characteristics of the dogs were not influenced by the enzyme supplementation (P>0.05). An increase in the level of inclusion of RSBM and HSBM reduced the DM content, faecal score (looser stools), and pH, whereas the volume of the faeces produced was increased (P<0.05). Enzyme supplementation increased palatability, the DM and CP digestibility, and the ME content of dog foods containing up to 300 g of the two SBM/kg.