R. Toullec

Activity distribution of seven digestive enzymes along small intestine in calves during development and weaning

Ten groups of calves were used to study the changes in activity levels and distribution of seven hydrolases in the intestinal mucosa during development and weaning. The calves in the first group were sacrificed at birth while those in the remaining nine groups were either milk-fed until slaughter on days 2, 7, 28, 56, 70, and 119; or weaned between days 28 and 56 and then slaughtered on days 56, 70, and 119, respectively. The small intestine was immediately cut off and divided into five segments, ie, duodenum, proximal jejunum, median jejunum, distal jejunum, and ileum. In the milk-fed animals, the activity levels of aminopeptidases A and N, alkaline phosphatase, lactase, and isomaltase were maximum at 2 days of age, and then declined sharply between days 2 and 7 but did not change significantly thereafter. By contrast, the maltase activity increased between days 7 and 119, while no sucrase activity was detected. Weaning resulted in a decrease in the activity of lactase and an increase in that of aminopeptidase N, maltase, and isomaltase. The distribution of all these enzymes along the small intestine was slightly influenced by age but not at all by weaning.

Specific regulation of the gene expression of some pancreatic enzymes during postnatal development and weaning in the calf.

The construction of cDNA library from calf pancreas allowed us to examine the mRNA levels of four pancreatic hydrolases (chymotrypsin, lipase, trypsin and amylase) during postnatal development in preruminant and ruminant animals. The lack of parallel variations in the levels of the enzyme specific activities suggested that protein synthesis was not coordinately regulated. In preruminant calves, the change in chymotrypsin and lipase mRNA concentrations (0-28 day period) and in trypsin mRNA concentrations (0-119 day period) was opposite to that in the corresponding specific activities. In contrast, both the activity and mRNA profiles of amylase during the latter period, on the one hand, and those of chymotrypsin and lipase during the 28-119 day period, on the other hand, were comparable. However, the extent to which the specific activity and mRNA concentration of each enzyme were increased did not necessarily coincide. The observed changes in mRNA levels probably resulted from some transcriptional control of the gene expression and/or variation in mRNA stability. Moreover, a translational regulation of the messengers could explain the existence of non-parallel mRNA and specific activity profiles. In sharp contrast with the multiple control of protein synthesis during postnatal development in preruminant calves, weaning was found to induce the same increase in enzyme activity and corresponding mRNA for each of the four pancreatic enzymes, suggesting that pretranslational modulation of gene expression was mainly, if not exclusively, concerned.

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.

Early-life patterns of plasma gut regulatory peptide levels in calves. effects of age, weaning and feeding

1. The effects of age, weaning and feeding on the release of seven gut regulatory peptides [gastrin, cholecystokinin (CCK), secretin, vasoactive intestinal peptide (VIP), pancreatic polypeptide (PP), motilin and somatostatin] were studied in calves either exclusively milk-fed between birth and 91 days (P group) or weaned between 22-56 days of age (R group). 2. During the first 3 weeks, the basal plasma immunoreactive levels increased with age for secretin, CCK and PP, decreased for gastrin, motilin and somatostatin and were unaffected for VIP. The changes were particularly rapid for somatostatin and gastrin. After 3 weeks, no significant trend was observed with age in the P group. 3. Weaning resulted in an increase of basal gastrin, CCK, PP and VIP and in a decrease of basal secretin and somatostatin. 4. In the P group, the morning meal was followed 1 hr later by an increase of gastrin and CCK, and by a fall of secretin, PP, motilin and somatostatin, but no significant effect was observed in VIP. Weaning resulted in a reduction of the differences between the fasting and the post-feeding values. 5. These changes suggest a large involvement of endocrine cells in the adaptation of gut tissues, secretions and motility at birth, during the maintenance at the pre-ruminant stage and at weaning.

Early-Life Patterns of Plasma Gut Regulatory Peptide Levels in Calves: Effects of the First Meals

The effects of the first meals on the release of seven gut regulatory peptides were studied in newborn calves fed colostrum either at serial intervals during the first day of life or at 28 h only. Fasted animals showed no significant variation of plasma peptides until the first feed, except for somatostatin, which peaked at 4-5 h and declined thereafter. As assessed before and 1 h after feeding, the first meal tended to induce rises in plasma gastrin, cholecystokinin and pancreatic polypeptide, while the other peptides were unaffected. Repeated colostrum feeds induced marked increases in plasma gastrin, cholecystokinin, secretin and vasoactive intestinal peptide from 10 h on. Pancreatic polypeptide was transiently increased from 4 to 16 h. Feeding was followed by a transitory reduction of plasma somatostatin and by a prolonged decrease of plasma motilin. We conclude that colostrum feeding potently modulates the release of several regulatory peptides shortly after birth in calves. These responses may be important for the adaptation of gut growth, secretions and motility to food ingestion in the neonatal period.

Replacement of skim milk with soya bean protein concentrates and whey in milk replacers for veal calves

Abstract Two experiments were conducted at a 1 year interval to study the nutritional utilization by veal calves of milk replacers containing either milk protein (skim milk powder and/or whey) as the only sources of protein in controls or a mixture of whey protein and various commercial soya bean protein concentrates (SPC). A water-extracted SPC (SPC 1) and a SPC treated with hot aqueous ethanol (SPC 2) were incorporated at 65% (crude protein basis) in formulas studied in Experiment 1. The SPC 1 was highly antigenic in vitro while SPC 2 was not. Recently, in vitro antigenicity of SPC 1 was drastically reduced by extra treatments. The new product obtained (SCP 3) provided 72% of protein in the formula of Experiment 2. All these milk replacer diets were given to 4- to 5-week-old veal calves for 101–103 days. Apparent digestibility of feed constituents and nitrogen retention were measured between 9–14 (Experiments 1 and 2) and 51–56 (Experiment 1) or 65–70 (Experiment 2) days from the beginning of dietary treatment. The SPC adversely affected final live weight (LW), LW gains and feed conversion ratios over the experimental period. Digestibility of feed constituents was also most often significantly reduced with SPC-based diets, regardless of age. For example, N digestibility was 16% and 9% lower with the SPC 1 and SPC 2 diets, respectively (Experiment 1), and 10% lower with the SPC 3 diet (Experiment 2) than with the control diet. Digestibility of N in SPC products was calculated to be 71%, 81% and 81% for SPC 1, SPC 2 and SPC 3, respectively. Thus, reducing the antigenic activity of SPC 1 increased the digestibility of its N by 14%. Nitrogen retention was also usually lower with diets containing SPC than with controls. In terms of immunogenicity, calves given the SPC 1 and SPC 3 diets displayed low antibody titres. This was unexpected from in vitro data found with SPC 1. Calves given the SPC 2 diet had no detectable anti-soya antibodies. It is concluded that the SPCs tested in the present study could not replace so high a proportion of dairy protein without adversely affecting calf performance. This may have resulted mainly from a lower digestibility of soya N rather than from adverse reactions to soya since specific antibody titres remained low to moderate.

Digestion of wheat protein in the preruminant calf : ileal digestibility and blood concentrations of nutrients

Three milk substitute diets (control, SWP76 and SWP36) were given to ileo-caecal cannulated preruminant calves. In these diets, skim milk powder was either the only protein source or totally or partially (48%) replaced by a mixture of solubilized wheat protein concentrate (SWP) and whey powder (76% and 24%; crude protein basis), respectively. The apparent ileal digestibility of nitrogen was lower (P<0.02) with the SWP76 and SWP36 diets than with the control (0.85, 0.89 and 0.91, respectively) and also with the SWP76 than with the SWP36. Similar trends were observed for most amino acids (AA), except for cystine which showed higher values with the SWP-containing diets than with the control (P<0.05). Assuming the true digestibility of milk protein was total, the real digestibility would be ≥0.95 for most essential AA of SWP+whey proteins. Repetitive fractions rich in glutamine, proline and phenylalanine, which are abundant in wheat protein, appeared to partially escape digestion. The amount of undigested endogenous protein could also be slightly higher (7–17%) with the SWP-containing diets than with the control. The pre-feeding plasma concentrations were lower (P<0.001) with the SWP76 than with the control for triglycerides and similar with both diets for free methionine and threonine. In contrast, most post-feeding values were higher (P≤0.05) with the SWP76 than with the control. The SWP36 diet gave values or patterns intermediate to those recorded with the other diets. Most of these differences were consistent with a faster abomasal emptying for fat and protein with the SWP-containing diets, especially the SWP76. As far as threonine and methionine were concerned, they could also have been increased by the fact that larger parts of these AA were free in the SWP-containing diets.

Roasted fullfat soybean as an ingredient of milk replacers for goat kids

Abstract The present work was aimed at studying simple methods for processing fullfat soybean, and at designing soy-based milk replacers suitable for goat kids. Soybean was roasted at 100°C for 10 (HSF10) or 30 (HSF30) min. The residual antitryptic activity and immunoreactive glycinin and β-conglycinin, respectively, were 40, 17 and 5% for HSF10, and 20, 6 and 3% for HSF30, of those in raw soybean. Milk replacers containing 24% CP and 22% fat were prepared. In the control diet, skim milk powder and sweet whey provided 95 and 5% of total protein, respectively. In the soy-based diets, 45% of total protein was from either the HSF10 or the HSF30 flour, the remainder being provided by skim milk powder and sweet whey (45 and 10% of total protein, respectively). These diets were given as liquid milk replacers to 20 goat kids (n=6, 8 and 6 for control, HSF10 and HSF30 treatments, respectively) between 14 and 50 days of age. Nutrient digestibility and N balance were measured twice over 5 days starting at 26 and 40 days of age. Growth and DM intake were not significantly different between treatments. The digestibility of N was lower for the soy-based diets as compared with the control diet. It did not change significantly over time for the control and HSF10 diets (average values of 0.915 and 0.67, respectively) but it increased significantly from 0.70 to 0.80 for HSF30 between the two measurement periods. Direct skin tests carried out with soybean protein extracts after the second measurement period revealed only delayed reactions to HSF10 extracts in the HSF10 group. Roasting fullfat soybean at 100°C for 30 min appeared to provide a milk replacer ingredient nutritionally more acceptable for rearing kids than roasting for 10 min.

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.

Antigenicity and digestive utilization of four soya products by the preruminant calf

Abstract A study was conducted to study the utilization by preruminant calves of commercial or experimental soya products variously treated and to ascertain whether differences among products for nitrogen digestibility could be linked with their in vitro antigenicity. Four milk replacers containing a mixture of skim milk powder and soya products (40:60, protein basis) were fed to 3-week old calves for 102 days at a rate increasing progressively from 1050 to 2700 g DM/day. Two heated soyabean flours (antigenic: ASF, or non-antigenic: NASF) and two soyabean protein concentrates (water extracted, antigenic: ASC or protein hydrolyzed, non-antigenic: NASC) were compared. Antigen immunoreactivity in vitro was high in ASF and ASC, low in NASF and not detectable in NASC. Growth performance and antisoya antibody production were recorded throughout the trial. Digestibility and nutrient retention were measured between 16–21 and 55–60 day of the experiment. Live weight gain was lower (16%, P