In vitro gastrointestinal simulation digestion, absorption and bioavailability of four animal-based proteins in canine and feline food.

With increasing emphasis on companion animals, the nutrition and health of companion animals are attracting more and more concerns. In this work, digestive properties and in vitro bioavailability index (IVBAI) of four animal-derived proteins (casein, casein phosphopeptide, collagen and gelatin) in canine and feline food were evaluated using in vitro simulated digestion and cell absorption experiments. The results of high-performance liquid chromatography (HPLC) demonstrated that arginine, serine, lysine and glycine were produced during gastrointestinal digestion of four proteins. Meanwhile, the scale of peptides produced by digestion as determined by liquid-mass spectrometry (LC/MS) were mainly concentrated below 2000 Da. Digestion kinetic results indicated that casein phosphopeptide (CPP) and collagen (Col) could be digested faster by canine and feline compared with other proteins. It is worth noting from the intestinal absorption of Caco-2 cells that more than 13 amino acids could be absorbed, but the peptides digested could be not easily transported through cells. Finally, higher IVBAI in canine was confirmed to be Col and CPP, reaching respectively 25.60%±1.28% and 12.30%±0.61%, while it in feline was confirmed to be gelatin (Gel) and CPP, reaching 24.70%±1.23% and 19.30%±0.96%, respectively. These results indicated that Col and CPP could be more easily digested and absorbed in canine, while Gel and CPP could be more easily digested and absorbed in feline. These findings could provide important reference for the selection of animal proteins and nutritional enhancement of pet food.