PSX-8 - Effect of feeding additional whey protein to senior Labrador retrievers for maintaining lean mass and minimizing inflammation

Abstract: We previously reported increases in lean mass and lean:fat ratio in senior Labrador Retrievers fed a commercial whey protein supplement after a 26-week trial with exercise regimen. Further work on this project examined the impacts of this supplement on immunity and inflammation. Thirty-six senior ( >7 yr) Labrador Retrievers received a basal diet meeting AAFCO crude protein (CP) requirements (45g/1000 kcal, 18% CP on DM basis) and were randomly assigned to one of three supplements: 1) an additional 22.5 g CP/1000 kcal (27% CP on DM basis) sourced from hydrolyzed pea protein isolate (Pea); 2) additional 22.5 g CP/1000 kcal (27% CP on DM basis) sourced from whey protein (Whey; Hilmar Protelyze™ Pet; Hilmar, CA) or 3) poultry fat and sucrose to equalize calories but provide no additional CP (Control). All dogs participated in an exercise regimen consisting of twice weekly 2.2 km runs. Blood samples were collected via jugular venipuncture at week 0 (baseline) and week 26 (end of trial) for analysis of cytokines (IL-2, IL-6, IL-8, IL-10, IL-12, NGF-β, IFN-γ, TNF-α, MCP-1, VEGFA, SCF) and immune cell proliferation. Cytokines were measured with Luminex MAGPIX analyzer. Peripheral blood mononuclear cells were isolated from whole blood, plated, challenged with pokeweed mitogen. Proliferation was evaluated with a 5-bromo-2’-deoxyuridine proliferation assay kit. Gait analysis was evaluated at weeks 0 (baseline), 4, 8, 16 and 26 using a Gait4Dogs pressure walkway (CIR Systems, Inc; Franklin, NJ). Gait data was processed to generate a FRK Total Gait Inflammation Index, calculated by the sum of the differences from the ideal scores for gait lameness score, total pressure index, step/stride ratio, and hind reach. Data were analyzed using one-way ANOVA with Tukey’s post-hoc adjustments. We observed increases in IL-12 (P = 0.004), MCP-1 (P = 0.04), VEGFA (P = 0.05), and SCF (P = 0.04) in Control vs Whey at week 26, with Pea intermediate. Spontaneous immune cell proliferation was lower in both Pea and Whey compared to Control (P < 0.01). Proliferation after challenge was lower in Whey compared to Pea (P = 0.05), with Control intermediate. The FRK Total Gait Inflammation Index significantly increased after exercise in Control and Pea dogs, but not Whey (P < 0.01). Control dogs’ scores remained elevated compared to Whey dogs from weeks 4 to 26 (P < 0.01). Dietary supplementation with whey protein at 1.5 x AAFCO minimum proved beneficial for Labrador Retrievers by maintaining more lean mass with improved lean/fat ratio, reduced inflammatory biomarkers, immune cell proliferation, and FRK Total Gait Inflammation Index after an exercise regimen when compared to seniors only consuming a 18% protein basal diet. Supplemental whey protein may better maintain senior dogs experiencing chronic inflammation from aging or disease.