Effect of some technological treatments of milk amino acid composition of in vivo effluents during gastric digestion

The effects of technological treatments of milk on the in vivo amino acid (either in the peptidic or in the proteic form) gastric emptying of preruminant calves were studied with three different diets: raw skim milk (RSM), pasteurized skim milk (PSM), and pasteurized and acidified skim milk (Y). The emptying of casein and whey proteins was evaluated from the amino acid compositions obtained by acid hydrolysis of the effluents leaving the stomach during 12 h. From these compositions, the emptying kinetics of each amino acid, essential and hydrophobic amino acids, were also considered. It was found that casein was emptied as was the fresh matter with Y and retained longer in the stomach with RSM and PSM because of its coagulation. Since interactions occurred during heating between casein and whey proteins, whey proteins were emptied as was the fresh matter with Y and RSM, whereas they were also retained with PSM. Gastric emptying kinetics of some amino acids (Asx, Pro, Leu, Thr, Tyr, Phe) were significantly affected by milk process. Consequently, the pool of amino acids entering the duodenum varies with time and diet also. Consequences of these variations are discussed