Influence de la cinétique d'évacuation gastrique de l'aliment sur l'insulinémie chez le veau préruminant

: The aim of this work was to clarify the possible role of blood metabolites (glucose, aminoacids, triglycerides) in the regulation of postprandial blood insulin in the preruminant calf. The animals used were 6 male Friesian bull calves with an average weight of 80 kg. They were divided into groups I and II. During the first experimental period (A), group I received a control diet that contained skim-milk powder as the only protein source, whereas group II received an experimental diet containing fish protein concentrate as the main protein source. During the second experimental period (B), the diets were switched. It was previously shown that the rate of fat and amino acid absorption increased when milk proteins in such milk substitutes were replaced by hydrolyzed fish proteins (Guilloteau et al., 1975). The results showed that during any experimental period in the control group, there was a decrease in the postprandial blood free amino nitrogen. Blood triglycerides exhibited a small increase at 0.5 h after the meal but a large decrease at 1-4.5 h. The meal also resulted in a very large increase in blood glucose with maximal values occurring at 1-4.5 h. Blood insulin showed a large increment at 0.5 h then increased slowly, peaking at 2-3 h. The postprandial increase in blood insulin was less during the first experimental period than during the second one. In calves fed the fish diet, blood free amino nitrogen and blood triglycerides showed a large postprandial increase. Blood glucose exhibited a smaller postprandial increment than in the controls and began to decrease at half an hour. In contrast, the trend of changes in blood insulin was the same as in the controls (i.e. a maximum at 3 h occurring after a large increase at 0.5 h). There were no significant differences in blood insulin between the two experimental periods. It was lower in the calves fed the fish diet than in the controls during the first experimental period; during the second period, it was similar in both groups. From these observations, it may be inferred that, as compared to the control diet, the fish diet resulted in a decrease in glucose stimulation of postprandial insulin secretion; in contrast, the effect of aminoacids and lipids may be increased.