Protein-Deficient Diet Alters Serum Alkaline Phosphatase, Bile Acids, Proteins and Urea Nitrogen in Dogs

Abstract

Inadequate dietary protein intake in dogs can occur in a number of clinical situations, including prolonged voluntary anorexia, feeding of improperly formulated homemade diets (i.e., vegetarian) and overzealous protein restriction for the management of hepatic dis ease, renal insufficiency or struvite urolithiasis. Pre liminary data in our laboratory and others (Osborne et al. 1985) suggested that restricted protein diets (8% dry matter basis (DMB) ) can result in mild abnormal ities in a number of common serum biochemical assays including serum albumin, urea nitrogen and alkaline phosphatase. For that reason, a study was undertaken to assess the effect of an overtly protein-deficient diet on serum biochemical assays and hepatic function tests. Materials and methods. A prospective random ized study was designed to evaluate the effects of a protein-deficient diet on serum proteins, urea nitro gen, hepatic enzymes and bile acids. This experiment was one component of a larger study evaluating the effects of protein deficiency on bone healing in dogs. The experimental protocol was reviewed and approved by the institutional Animal Care and Use Committee of the Akron City Hospital. Sixteen healthy adult female beagles were utilized in the study. Dogs were determined to be healthy be fore the study on the basis of a physical examination, complete blood count, serum biochemistry panel and urinalysis. Eight of the dogs consumed a control diet for the entire 6-mo course of the study. The remaining eight dogs were fed a protein-deficient diet. Dogs were randomly assigned to each feeding group. Dogs were housed individually and were meal fed an amount cal culated to maintain their body weight. To detect ex ternal evidence of protein malnutrition, physical ex ams were performed on each dog weekly. Body weights were also recorded weekly. Table 1 outlines the nutrient profile and metabolizable energy content of the two experimental diets used in the study. Table 2 provides the ingredient composition of the two diets. Both diets were for mulated and manufactured by the Experimental Food Laboratory at Mark Morris Associates (Topeka, KS) using a twin screw extruder (APV Baker, Grand Rap ids, MI) for the cooking and forming process. The amino acid sources in both the control and pro tein-deficient diets were egg and food grade cornstarch. Egg was an important source of protein in both the protein-deficient (80%) and control (95%) diets. Amino acids contained in the cornstarch supplied ~20% and 5% of the protein in the protein-deficient and control diets, respectively. The amino acid profile of the control diet exceeded the canine amino acid re quirements established by Association of American Feed Control Officials (1994) and the National Re search Council (1985). Jugular venipuncture was performed after witholding food for 12 h at 0 (baseline), 4, 8, 12, 16 and 24 wk of the study. Venous blood was also sampled preand postprandially (2 h) during weeks 12 and 24 for serum bile acid analysis. Serum was harvested im mediately and frozen at -70°C pending analysis.