In Vivo and In Vitro Gastric Emptying of Protein Fractions of Milk Replacers Containing Whey Proteins

Abstract

In vivo and in vitro gastric emptying of protein fractions of three milk replacers containing either milk protein (control), a mixture (50:50 on a CP basis) of milk protein and native whey protein concentrate, or a mixture (50:50 on a CP basis) of milk protein and heated whey protein concentrate was studied. In vivo gastric emptying was measured in three preruminant calves fitted with reentrant duodenal cannulas and used in a 3 × 3 Latin square design. In vitro gastric emptying was determined after enzymatic digestion in an artificial stomach. In vivo and in vitro flow rates of protein N (12% TCA-insoluble N) and total N were higher for milk replacers containing whey proteins than for control. Gastric emptying of NPN (12% TCA-soluble N) was slightly higher for diets containing whey proteins than for that containing milk proteins. Gastric emptying of all protein fractions was similar for the two milk replacers containing whey proteins. In vivo and in vitro results were significantly correlated, suggesting that the in vitro method reproduced conditions for proteolysis and could be used to predict gastric digestion of protein fractions.