Soy Protein Isolate versus Meat-Based Low-Protein Diet for Dogs with Congenital Portosystemic Shunts

Background: Both presurgical preparation and long-term support of nonoperable dogs with congenital portosystemic shunts (CPSS) require optimal dietary management. Studies suggested that protein source may play an important role, with vegetable and dairy protein sources having better effects on hepatic encephalopathy (HE) than meat proteins.
Objectives: Determine whether a low-protein test diet with soy as its main protein source results in better scores than a control diet with the same composition but with poultry as its main protein source in dogs with CPSS.
Methods: In a double-blind cross-over study, 16 dogs received each diet for 4 weeks. Dogs in group T first received the test diet and then the control diet, whereas dogs in group C were fed the diets in the opposite order. Different variables (body weight, body condition score, HE score, fecal score, CBC, plasma tests of liver function including NH₃, and coagulation tests) were measured at the start of the study and after completion of each diet.
Results: One-way repeated measures ANOVA was performed. Plasma NH₃ was significantly lower after the test diet than after the control diet. The test diet also resulted in significantly higher fibrinogen concentrations and lower prothrombin times. The HE score improved with both diets, with no significant difference between the 2 diets.
Conclusions: Both diets achieved a significant improvement in HE score. The influence of the soy-based diet on plasma NH₃ concentration and coagulation parameters suggests that such a diet decreases the risk for HE and gives better support of liver function.