Hydrolysed Poultry Byproduct Meal Effects on Metabolic, Inflammatory, Immunologic, and Lipidemic Parameters in Beagle Dogs

Protein hydrolysates may contain bioactive peptides that influence metabolic and physiological responses. This study evaluated the effects of hydrolysed poultry byproduct meal (HPM), replacing conventional poultry byproduct meal (PBM), on selected antioxidant, inflammatory and metabolic parameters in dogs. Four extruded diets were formulated: a control diet with PBM as the protein source and diets replacing 25%, 50%, and 100% of PBM protein with HPM protein. Thirty-two Beagle dogs were included (eight dogs per diet) and were fed the respective diets for 32 days. Outcomes assessed included total cholesterol and lipoprotein fractions, oxidative stress markers, serum angiotensin-converting enzyme (ACE) activity, systemic blood pressure, urinary parameters, renal electrolyte excretion, serum cytokines, phagocytic activity of neutrophils and monocytes, and faecal IgA levels. Data were analysed using ANOVA, with means compared through polynomial contrasts based on HPM inclusion levels (p < 0.05). Diet had no effect on blood pressure, ACE activity, serum triglycerides, phagocytic index, or oxidative parameters (p > 0.05). However, urine sodium concentration and renal excretion increased linearly, while urine pH decreased quadratically with HPM inclusion (p < 0.01). Serum cholesterol decreased quadratically (p < 0.01), and LDL cholesterol was lower in dogs fed 100% HPM compared to control diet (p = 0.030). Dogs fed 100% HPM had lower IL-2 and TNF-α levels than dogs fed other diets (p < 0.05), and their IL-6 and IL-10 levels were lower than those of dogs fed 25% and 50% HPM (p < 0.05). Faecal IgA increased linearly, with the highest value observed in dogs fed 100% HPM (p = 0.048). In conclusion, HPM intake modulated serum cytokines and faecal IgA concentrations, suggesting an impact on inflammatory and immune responses, while also increasing renal sodium excretion and reducing serum cholesterol. These physiological effects warrant further exploration in dogs with specific disease conditions.