SOURCE OF DIETARY-PROTEIN INFLUENCES KINETICS OF PLASMA GUT REGULATORY PEPTIDE CONCENTRATION IN RESPONSE TO FEEDING IN PRERUMINANT CALVES

The kinetics of the peripheral plasma concentrations of eight gut regu latory peptides were examined in response to feeding in preruminant ca lves. Two experiments were carried out in animals fed milk substitutes either based on milk protein (control diet) or in which casein had be en replaced by hydrolyzed fish (fish diet in experiment 1) or whey (wh ey diet in experiment 2) protein concentrate. In contrast to the contr ol diet, the latter two did not coagulate within the abomasum,No varia tion was observed in plasma concentrations oi gut regulatory peptides during 1-1.4 hr before the morning meal regardless of the nature of th e dietary protein. With the control diet, the meal was followed by an increase in cholecystokinin, gastrin and gastric inhibitory polypeptid e and a fall in secretin, vasoactive intestinal polypeptide and motili n, whereas no significant change was observed for somatostatin and pan creatic polypeptide. The replacement of casein by protein substitutes did nut greatly modify the pattern of plasma responses to feeding, but the prefeeding and postfeeding levels were highly affected. We conclu de that the most important characteristic influencing plasma gut pepti de concentrations is the ability of dietary protein to clot in the abo masum, consequently determining the pattern of gastric emptying, and t hat variations appear depending on the origin of protein substitutes i n relation to the duodenal content and mainly to the digesta pH. (C) 1 998 Elsevier Science Inc.