Intragastric bolus feeding of meals containing elementary, partially hydrolyzed or intact protein causes comparable changes in interorgan substrate flux in the pig

Dietary protein given as pre-digested protein improves the nutritional value of the meal. However, studies measuring absorption kinetics of pre-digested protein or free amino acid mixtures are scarce and suffer from methodological problems. Therefore, the study was designed to study whether differences in absorption kinetics play a role. The kinetics of substrate production or consumption after a rapid gastrically-infused meal was studied across the portal drained viscera, liver and hindquarter in conscious, multicatheterized healthy pigs of 20-22 kg (n = 12). The meal contained carbohydrates and protein (1.44 g/kg body weight) as intact whey protein isolate, moderately-hydrolyzed protein digest or equivalent amino acid mixture (including glutamine and asparagine). For almost all amino acids and glucose, intestinal production, liver and hindquarter uptake were similar.The higher liver urea production (less than 15% of total alpha-amino intake) after the meals with pre-digested protein or free amino acids was related to the marginally higher intestinal glutamine breakdown (not significant) and ammonia production. Our results suggest that in the normal healthy pig, uptake and metabolism of moderately hydrolyzed,free amino acid or intact protein meals with identical composition is not different.