The effects of chicken hydrolyzed proteins in extruded diets on plasma and fecal metabolic profiles in adult dogs

Research has shown various hydrolyzed proteins possessed beneficial physiological functions; however, the mechanism of how hydrolysates influence metabolism is unclear. Therefore, the current study aimed to examine the effects of different sources of protein hydrolysates, being the main dietary protein source in extruded diets, on metabolism in healthy adult dogs. Three complete and balanced extruded canine diets were formulated: control chicken meal diet (CONd), chicken liver and heart hydrolysate diet (CLHd), mechanically separated chicken hydrolysate diet (CHd). A replicated 3 × 5 Latin rectangle design was used with 10 adult beagles. Within each period, the assigned diets were fed to the beagles for 28 days after a 7-day wash out period. Plasma and fresh fecal samples were collected at day 28. Samples of diets, plasma, and feces were analyzed for global metabolomics with ultra-performance liquid chromatography and quadrupole-Orbitrap high-resolution mass spectrometer interfaced with a heated electrospray ionization source and mass analyzer. In general, there were lower fecal concentrations of dipeptides and protein degradation metabolites, indicating higher protein digestibility, in dogs fed protein hydrolysate diets in contrast with CONd (q < 0.05). Higher plasma pipecolate and glutamate, higher fecal spermidine and indole propionate, and lower phenol-derived products in both plasma and feces were found in CLHd group than CONd (q < 0.05), indicating lower oxidative stress and inflammation levels. The main difference in lipid metabolism between CHd and CONd was the bile acid metabolism, showing lower circulating bile acid, lower unconjugated bile acid excretion and higher taurine-conjugated bile acid excretion in the CHd group (q < 0.05). In conclusion, using chicken hydrolysates as the main protein source in extruded canine diets showed potential for physiological benefits in healthy adult dogs, especially protein hydrolysate from chicken heart and liver demonstrated effects on lowering inflammation and oxidation levels.