Abstract
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. Plasma and fresh fecal samples were collected at day 28. Samples were analyzed for global metabolomics with ultra-performance liquid chromatography and high-resolution mass spectrometer interfaced with a heated electrospray ionization source and mass analyzer. In general, there were lower 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 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).