Protein digestion in weanling pigs: effect of feeding regimen and endogenous protein secretion.

Protein digestion and absorption were measured in weanling pigs (5 wk of age) using a total digesta collection procedure. In the first experiment, the objective was to measure the fate of nitrogenous digesta as it passed from the stomach to the terminal ileum when pigs were either allowed ad libitum access to feed or were fed four equal meals per day. Pigs were fed a standard corn-soybean meal diet in this experiment. There were no differences in flow rate or retention time of dry matter or nitrogen, and no differences in apparent nitrogen digestibility between the two feeding regimens. More than 80% of the soluble protein in the stomach and 65% in the small intestine was between 2,000 and 15,000 molecular weight. The molecular weight profiles of the soluble proteins were relatively constant throughout the small intestine, indicating that the products of protein hydrolysis were absorbed rapidly. The objective of the second experiment was to compare protein digestion and absorption in pigs fed a corn-soybean meal diet with those fed a protein-free diet. The molecular weight profiles of soluble protein were similar for the two groups of pigs. The data indicate that most of the endogenous enzymes were hydrolyzed rapidly, since little soluble protein corresponding to the molecular weight of pancreatic enzymes was detected.