G. Le Dréan

Kinetics of pancreatic exocrine secretion and plasma gut regulatory peptide release in response to feeding in preruminant and ruminant calves.

Pancreatic exocrine secretion and plasma cholecystokinin, gastrin, secretin, and somatostatin concentrations were examined in relation to feeding in 70- to 120-day-old preruminant and ruminant calves. The apparatus used was designed to immediately re-infuse the animals own pancreatic juice and to carry out accurate measurements of the juice flow in real time and to take samples. In the preruminants, pancreatic juice, protein, and trypsin flows increased from 45 min before and until 15 min after the meal and decreased sharply thereafter over a period of 30 min. while protein and trypsin concentrations peaked after feeding. A significant increase in plasma gastrin and cholecystokinin (CCK), a fall in secretin and no change in somatostatin were observed after milk ingestion. By contrast, in the ruminants, feeding had no effect on the pancreatic secretion and on the plasma concentrations of these peptides. Similar and simultaneous patterns of juice flow and secretin, as well as of protein and trypsin concentrations, CCK and gastrin, could support the hypothesis that these gut regulatory peptides play a significant role in the regulation of the pancreatic function. In preruminant calves, the existence of cephalic, gastric and intestinal phases is discussed. In the ruminants, that of the ruminal phase is questionable.

Gut regulatory peptide levels in bovine fetuses and their dams between the 3rd and 9th months of gestation.

Several gut regulatory peptides were measured by radioimmunoassay between 3 and 9 months of gestation in the plasma of 91 bovine fetuses and their dams, in fetal gastric content and in amniotic fluid. During gestation, plasma peptide concentrations did not change in cows. Likewise, fetal plasma concentrations of cholecystokinin, somatostatin, secretin and vasoactive intestinal polypeptide showed no variation while those of gastrin, pancreatic polypeptide and gastric inhibitory polypeptide increased during the last 6 months. Peptide levels in the fetus were higher than or equal to maternal concentrations. At 8–9 months of gestation, gastrin, CCK, secretin and somatostatin concentrations in amniotic fluid were lower than those measured in fetal gastric content and in maternal and fetal plasma. Therefore, a substantial endogenous endocrine production of regulatory peptides by the fetus probably exists as early as the third month of gestation, accompanied by a release into the lumen of the gut.

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 regulatory peptides were examined in response to feeding in preruminant calves. Two experiments were carried out in animals fed milk substitutes either based on milk protein (control diet) or in which casein had been replaced by hydrolyzed fish (fish diet in experiment 1) or whey (whey diet in experiment 2) protein concentrate. In contrast to the control diet, the latter two did not coagulate within the abomasum. No variation was observed in plasma concentrations of gut regulatory peptides during 1-1.4 hr before the morning meal regardless of the nature of the dietary protein. With the control diet, the meal was followed by an increase in cholecystokinin, gastrin and gastric inhibitory polypeptide and a fall in secretin, vasoactive intestinal polypeptide and motilin, whereas no significant change was observed for somatostatin and pancreatic polypeptide. The replacement of casein by protein substitutes did not greatly modify the pattern of plasma responses to feeding, but the prefeeding and postfeeding levels were highly affected. We conclude that the most important characteristic influencing plasma gut peptide concentrations is the ability of dietary protein to clot in the abomasum, consequently determining the pattern of gastric emptying, and that variations appear depending on the origin of protein substitutes in relation to the duodenal content and mainly to the digesta pH.

Response of the Calf Pancreas to Differently Processed Soya Bean and Pea Diets

The purpose of this study was to determine the effect of replacing skim-milk powder by differently treated soya bean or pea products on growth, pancreas size and pancreatic enzyme activities in calves. Three separate experiments have been performed. In experiments 1 and 2, 28 and 21 male Holstein calves were divided into 4 or 3 groups, respectively, and fed either dairy products or milk substitutes in which protein was mainly provided by soya bean products differing in their protein concentration due to the technological processing applied. In experiment 3, 45 male Holstein calves were divided into 3 groups and were fed either dairy products, or raw or flaked pea flour as a protein source. After an experimental period of 99 +/- 4 days in experiments 1 and 2, and of 88 days in experiment 3, animal growth rate was significantly lower with raw pea flour (16%) and with the soya bean diet, which was highly concentrated in carbohydrates and allergenic proteins (13-27%). Pancreas weight decreased significantly (16-18%) with pea diets and tended to be lower (NS) with the water extracted, concentrated and heated flour (soya bean). Amylase-specific activity increased significantly (43%) with pea diets but showed opposite tendencies with the most refined soya bean products. Proteolytic enzyme activities were slightly influenced by dietary protein source, but this was not as obvious as in the literature reviewed. Specific messenger RNAs corresponding to amylase, trypsin and chymotrypsin seemed to increase (NS) with the soya bean diets, particularly with the less elaborated one. However, further investigations are required before any conclusions may be drawn concerning regulation levels of pancreatic adaptation to dietary protein. According to this study and the literature, results concerning pancreatic response to diets were different suggesting that the origin of soya bean, pea seeds and technological treatments applied to them were of great importance. Also, the level of incorporation into milk substitute and the presence of more or less antinutritional factors could influence pancreatic enzyme variations by complex mechanisms.

Method of Measurement of Pancreatic Elastase II Activity and Postnatal Development of Proteases in Human Duodenal Juice and Bovine and Porcine Pancreatic Tissue

A specific method for pancreatic elastase IIactivity analysis was developed. True elastase IIactivity could be discriminated from that of elastase Iand chymotrypsin. The postnatal development of four pancreatic proteases in the duodenal juice ofchildren and in the pancreatic homogenates of calves andpiglets was measured. The study was carried out onpatients without (14 children) and with (5 children) pancreatic insufficiency. Calves and pigletswere either milk-fed or weaned until slaughter atdifferent ages. Profiles of enzyme development wereglobally similar in milk-fed piglets and calves, while in children without pancreatic insufficiency,no significant change was observed between 4 and 168months. In children with pancreatic insufficiency,enzyme activity was low. In animals, elastase II and chymotrypsin activities were maximal at birth,decreased with age, and probably were associated withthe digestion of milk protein. In contrast, elastase Iand trypsin activities increased markedly after weaning in connection with the intake of solidfood.

Pancreatic nutritional response of preruminant calves: effects of different treated soybean diets

excluded due to large refusals. At the end of the experiment, liveweight (mean t SE) was lower with the soybean diets (136 ± 12 kg, 145 ± 4 kg, and 157 ± 4 kg for HSF, WEC and PHI, respectively) than with CTL diet (166 ± 2 kg) (P <_ 0.05 between HSF or WEC and CTL). The pancreas weight tended (NS) to be lower with the soybean diets (691 t 34, 633 ± 43. 640 t 32 mg/kg liveweight instead of710±31):a a similar tendency was recorded for the chymotrypsin and amylase activities, but only the difference for amylase between the PHI and the CTL diets was closed to the significance (table I). That trend was not apparent for the trypsin activity (data not shown). In the present experiment, the soybean products had less effects on the pancreas weight and protease activities than those recorded by Gorrill et al (1967) and Guilloteau et al (1986). In contrast, the decreased amylase activity has not been observed by these authors and could be related to the elimination of soybean carbohydrates in PHI. The relative mRNA levels were not significantly affected by soybean diets, but they all tended to be higher with the HSF diet. However, these variations were insufficient to indicate the mechanisms involved in the pancreas response to different soybean products. Further investigations are required.