Influence of dietary protein level and source on the course of protein digestion along the small intestine of the veal calf.

The objective of this study was to examine the effect of the dietary crude protein (CP) content and source on the distribution of digesta proteins and peptides according to their molecular mass along the small intestine of veal calves. Diets contained 14, 104, 205, and 279 g/kg of CP supplied by skim milk powder (SMP) in experiment 1. Diets contained only SMP or SMP plus proteins (1:1 on digestible CP basis) from either a soybean protein concentrate (SPC), an isolated soy protein partially hydrolyzed (HSPI), or a potato protein concentrate (PPC) in experiment 2. Duodenal, jejunal, and ileal digesta were collected from calves fitted with simple cannulae and continuously infused the milk replacers into the abomasum. The distribution of molecular mass (Mr) of proteins and peptides was studied by gel filtration chromatography. Increasing the dietary CP level of milk replacers increased the flow of oligopeptides and free amino acids in ileal digesta. Incorporating plant protein increased the flow of proteins with Mr > 20,000 in the duodenum and that of proteins and peptides with Mr < 10,000 in the ileum. Hydrolysis of oligopeptides and absorption may be a limiting step in the digestion of plant protein in the veal calf.

Intestinal digestion of dietary and endogenous proteins along the small intestine of calves fed soybean or potato.

This study was conducted to investigate the quantitative and qualitative changes in dietary and endogenous protein components along the small intestine of calves. They were fed milk replacers in which protein was provided either by skim milk powder alone, as control diet, or by skim milk powder and a soy concentrate, a partially hydrolyzed soy protein isolate, or a potato protein concentrate (1:1 on a CP basis). The calves were continuously infused with the liquid milk substitute diets into the abomasum. Duodenal, jejunal, and ileal digesta were collected through T-piece cannulas. Digestibility (corrected for total endogenous protein) of dietary protein and the concentration of dietary, host endogenous, and bacterial proteins were estimated from the AA composition of digesta using multiple linear regression. The apparent digestibility of feed components increased linearly between the duodenum and the ileum. It was lower with the diets containing plant protein than with the control, especially at the ileum (85% for CP with soy concentrate, 73% with soy isolate, and 81% with potato concentrate vs 91% with skim milk powder). The real digestibility of dietary protein at the ileum was estimated to be 96, 95, 94, and 99%, respectively, for each of the dietary components. The partition of protein components in digesta between dietary, nonspecific endogenous, specific host endogenous, and(or) specific bacterial proteins varied along the small intestine and between diets at a given site. Intestinal apparent reabsorption of host endogenous protein was estimated to be equivalent to at least 86% of the jejunum flow. To conclude, the lower apparent digestibility of the plant protein sources studied resulted more from an enhanced loss of host and bacterial endogenous proteins than from decreased hydrolysis of dietary protein and absorption of their AA.

Calf intestinal mucin: isolation, partial characterization, and measurement in ileal digesta with an enzyme-linked immunosorbent assay.

The aim of this study was to develop a specific ELISA for calf intestinal mucin to quantify its contribution to ileal endogenous losses. Mucin was isolated from intestinal scrapings by cesium chloride density gradient ultracentrifugation. The isolated mucin had a high concentration of glutamic and aspartic acids, threonine, and serine (13.2, 11.2, 9.6, and 9.2 mol % of total amino acids assayed, respectively). The carbohydrates present were (mol % of total hexoses): galactose 42.1, N-acetylglucosamine 24.1, N-acetylgalactosamine 23.6, fucose 4.7, mannose 3.1, and sialic acids 2.4. Amino acids and carbohydrates represented 52.6 and 47.4% of the mucin by weight, respectively. A rabbit hyperimmune plasma was raised against purified mucin and used to set up an ELISA. The linear range of this assay was 20 to 640 ng/ml. The plasma cross-reacted with calf abomasal and colonic mucin. It showed no cross-reactivity with nonmucin components and no reactivity with intestinal mucin from other animal species except for the rat. Mucin accounted for approximately 3.5% of the dry matter output at the ileum of calves fed a substitute milk based on skim milk powder. This represented a flow of 3.4 g of mucin/kg of dry matter intake. Mucin flow increased when dietary protein was provided by cow's colostrum. Finally, the developed assay is a suitable tool to investigate the impact of dietary factors on the flow of mucin along the gut of preruminant calves.

Influence of dietary protein level and origin on the flow of mucin along the small intestine of the preruminant calf.

The objective of this study was to investigate the effect of the dietary crude protein (CP) content and origin on the flow of mucin protein along the small intestine of the preruminant calf. Diets contained 1, 10, 20 and 28% of CP supplied by skim milk powder (SMP) in experiment 1. Diets differed by the nature of protein [soybean protein concentrate (SPC), partially hydrolyzed soybean protein isolate (HSPI) or potato protein concentrate (PPC)] in experiment 2. Duodenal, jejunal, and ileal digesta were collected from calves fitted with simple cannulae and continuously infused the milk replacers into the abomasum. In experiment 1, the basal flow of mucin protein was 1.1, 1.8, and 4.0 g/kg of dry matter intake at the duodenum, jejunum, and ileum, respectively. Mucin protein contributed to 19 and 40% of ileal loss of CP and lysine, respectively. When dietary CP rose from 1 to 28%, the flow of mucin protein increased at the duodenum (+300%). In experiment 2, the flow of mucin protein increased by 70% at the duodenum and at the jejunum when SMP was partially replaced by SPC and HSPI. With PPC, this flow increased at the duodenum (+24%) and ileum (+52%). These data demonstrate the importance of mucin as a source of endogenous nitrogen and the impact of dietary protein content and origin on this flow.

Immunochemical studies on gastric and intestinal digestion of soybean glycinin and beta-conglycinin in vivo.

Two experiments were conducted to study gastric and small intestinal digestion of soybean glycinin and beta-conglycinin in preruminant calves fed milk replacers containing a mixture of skim milk powder and antigenic heated soybean flour. In experiment 1, duodenal passage of immunoreactive beta-conglycinin lasted for a much longer time after the morning meal than that of glycinin. Western blotting revealed the early abomasal outflow of glycinin subunits that associated nearly intact basic polypeptides to partially degraded acidic polypeptides. Intact beta-conglycinin was evidenced at most sampling times. In experiment 2, intact basic glycinin (M(r) = 21000) associated with partially digested acidic glycinin (7000 < M(r) < 25000) was demonstrated in ileal digesta up to 8-10 h after the meal. beta-Conglycinin immunoreactivity could not be evidenced by Western blotting in ileal digesta.

Morphology and enzyme activities of the small intestine are modulated by dietary protein source in the preruminant calf.

A study was undertaken to assess the impact of the protein nature and soya antigenicity on the morphology and some enzyme activities of the jejunum in preruminant calves. Twenty Holstein calves fitted with a duodenal cannula were fed a liquid diet based on skimmed milk powder (SMP) for 2 weeks. They were then switched onto diets containing a mixture of SMP and either antigenic heated soybean flour (HSF; n = 12) or hypo-antigenic soya protein concentrate (SPC; n = 8) for 8 weeks, after which they were reverted back to the SMP diet for 2 weeks. The diets contained similar amounts of digestible nitrogen and energy, and were fed at a rate of 55 g DM/kg(0.75)/d. Proximal jejunal biopsies were collected just before (week 0), during (weeks 2 and 8) and after (week 10) feeding of the soya-based diets, and were used for morphology measurements and the determination of total alkaline phosphatase, lactase, amino-peptidases A and N, and dipeptidyl peptidase IV activities. Feed intake and growth were similar between the HSF and SPC groups during the experimental period. The effects of antigenicity and the antigenicity x time interaction were never significant (P > 0.05). Villus height decreased (P < 0.01) between weeks 0 and 2, and increased (P < 0.05) between weeks 8 and 10. Villus width increased between weeks 2 and 8 (P < 0.001). Crypt depth also increased between weeks 0 and 2 (P < 0.001). Specific activities of alkaline phosphatase (P < 0.01) and amino-peptidase N (P < 0.05) decreased between weeks 0 and 2. Conversely, those of alkaline phosphatase (P < 0.0001), lactase (P < 0.01) and dipeptidyl-peptidase IV (P < 0.0001) increased between weeks 8 and 10. Specific activities for lactase and amino-peptidase N decreased (P < 0.01) between weeks 2 and 8. The treatments had little effects on the amino-peptidase A activity. In conclusion, the present work demonstrated that soybean protein markedly depressed the morphology and most enzyme activities of the calf small intestine. On the contrary, the in vitro antigenicity of soybean protein had little influence on these parameters in this study.

Nutritional value of the proteins of soybeans roasted at a small-scale unit level in Africa as assessed using growing rats.

Increasing the roasting time of soybeans from 15 (RSF15) to 25 (RSF25) min led to an important decrease in the antitryptic activity and immunoreactivity of the storage globulins, but it did not seem to greatly affect the concentrations of the indispensable amino acids in the protein. The RSF15 and RSF25 flours were used as the only protein sources in balanced diets for growing rats, and they were compared to a diet based on casein in a pair-feeding experiment. When roasted as usually happens at the workshop level (RSF15), soybean flour induced a significant hypertrophy of the pancreas. Increasing the roasting time by up to 25 min considerably improved the nutritional value of the soybean protein, without apparent consequence on the levels of free amino acid pools in the plasma and muscles. The data also indicated that the tissues of the small and large intestines of the young rat were sensitive to the hyperactivity of the intestinal microflora, and also possibly to the residual activity of some antinutritional factors.

Small intestinal motility disorders in preruminant calves chronically fed a diet based on antigenic soya: characterization and possible mediators.

Intestinal motility disorders and some mediators implicated in these disorders were studied in preruminant calves that had been chronically fed a diet containing an antigenic heated soyabean flour (HSF) for 3 months. The calves in the present study had previously been shown to present strong immune reactions against soyabean proteins, as assessed through plasma antibody titres, direct skin tests and in vitro lymphoproliferation. Four of these calves sensitive to soya were fitted with an abomasal catheter and wire electrodes on the jejunum. Myoelectric activity was recorded over 7 h following test meals containing skim milk powder (SMP), HSF or a non-antigenic hydrolysed soya protein isolate (HSPI). The pattern of myoelectric complexes migrating to the jejunum was regular with SMP (mean durations of phases I, II and III: 26, 38 and 5.28 min, respectively). With HSF, diarrhoea appeared, and the total duration of phase I decreased from 149 to 68 min (P < 0.01) while that of phase II increased from 239 to 328 min (P < 0.01). The mean duration of phase III decreased from 5.3 to 3.9 min (P < 0.01). These changes, including diarrhoea, were substantially reversed by feeding HSPI. When promethazine, a H-1 histamine receptor antagonist, was administered i.v. prior to feeding HSF the number of phases I tended to decrease and diarrhoea virtually disappeared. In contrast, indomethacin, a cyclooxygenase inhibitor, had limited effects on motility patterns and diarrhoea. These disorders were partially reproduced by i.p. administration of platelet-activating factor (PAF) prior to feeding with SMP. These findings suggest that calves chronically fed antigenic soya suffer from immune-mediated motility disorders which are linked to histamine action via H-1 receptors, and possibly with PAF. The role of arachidonic acid catabolites of the cyclooxygenase pathway is probably minor.

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 animal's 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 peptides in young cattle and sheep.

This review summarizes recent advances on blood plasma patterns, receptors, secondary messengers and metabolism of gut regulatory peptides (i.e. gastrin, secretin, somatostatin, cholecystokinin, vasoactive intestinal polypeptide, pancreatic polypeptide, gastric inhibitory polypeptide, motilin), in young ruminants during fetal and perinatal stages, during the preruminant stage and at weaning. It also deals with their role in the digestive tract function and postabsorptive changes. Some pathological situations in young ruminants are considered. Recent molecular aspects of digestive enzyme synthesis are also reported.

Feeding heated soyabean flour increases the density of B and T lymphocytes in the small intestine of calves.

The effect of dietary antigens on the gut morphology and density of immune cells was studied in preruminant calves fed milk substitutes containing skim milk powder (SMP), non-antigenic hydrolysed soya protein isolate (HSPI) or antigenic heated soyabean flour (HSF) as their main protein source for 3 months. The height and perimeter of proximal jejunum villi were highest in the calves fed SMP and lowest in those fed HSF (P < 0.05). In contrast, the crypt depth and perimeter were apparently not influenced by the dietary treatments studied. This morphological alteration was associated with a dramatic infiltration of the lamina propria by B and T lymphocytes in the calves fed HSF (P < 0.01). Increased B cell density was essentially accounted for by IgA-, IgG1- and IgG2-bearing cells. The density of CD2-positive T lymphocytes increased (P < 0.01) in the jejunal lamina propria of HSF calves, involving helper (CD4+) and suppressor-cytotoxic (CD8+) T cell subsets. The density of gamma-delta (WC1+) T cells also increased (P < 0.01). The major change concomitantly observed in the villus epithelium was an increased density of CD8+ cells (P < 0.05) and WC1 + cells (P < 0.01).

Identification of soyabean allergens and immune mechanisms of dietary sensitivities in preruminant calves.

The allergenicity of soya proteins was assessed by direct skin testing and by in vitro lymphoproliferation tests in calves fed milk substitutes containing skim milk powder (SMP) or an antigenic heated soya flour (HSF). During the last three weeks of treatment, the calves were injected intradermally with raw soya flour (RSF), HSF, hydrolysed soya protein isolate (HSPI), SMP or purified soya proteins, after being premedicated with anti-histamine or not. Peripheral blood leucocytes (PBL) were grown over five days with various mitogens or dietary antigens, and the incorporation of tritiated thymidine was measured. Strong skin oedema reactions to RSF, HSF and all the purified proteins were observed in the calves fed HSF at various times up to 24 hours after injection. The skin oedema was largely prevented by premedication with anti-histamine. A strong delayed skin thickening was observed in the calves fed HSF for up to five days with beta-conglycinin. PBL from the calves fed HSF proliferated in vitro with HSF, HSPI and beta-conglycinin, but not with glycinin. Thus, most proteins from soyabean were implicated in the immediate and semi-delayed immune reactions, whereas beta-conglycinin was strongly involved in a delayed type hypersensitivity in calves.

Analytical criteria for predicting apparent digestibility of soybean protein in preruminant calves.

A series of experiments on the use of soybean as a protein source in milk replacers for veal calves was undertaken to determine the relationships between the physicochemical and antinutritional properties and apparent digestibilities of nine soybean products. Soybean provided between 58 and 71% of dietary CP, and skim milk or whey powder provided the remainder. Soybean products were analyzed for CP, native protein, aggregated protein, carbohydrate-linked protein, peptides, antitryptic activity, and immunoreactivity of lectin, glycinin, alpha-conglycinin, and beta-conglycinin. The apparent digestibility of N calculated for soybean protein varied between 59 and 84%. Simple linear correlations were significant between apparent digestibility of soybean N and concentrations of native protein, antitryptic activity, glycinin, alpha-conglycinin, and beta-conglycinin. However, only variation in antitryptic activity, alpha-conglycinin, and beta-conglycinin contributed significantly to an explanation for the variation in apparent digestibility of soybean N in a multiple linear equation. Under our experimental conditions, beta-conglycinin was the best predictor of digestibility of soybean N. Antitryptic activity became the best predictor when soybean products had no detectable beta-conglycinin.

Influence of soya antigen levels in milk replacers on the disruption of intestinal motility patterns in calves sensitive to soya.

An experiment was designed to determine the soya antigen levels in milk replacers above which gastrointestinal disorders appeared in preruminant calves previously sensitized to antigenic soya by feeding a soya-based milk replacer for 3 months. These calves were then equipped with wire electrodes on the duodenum and the mid-jejunum. The sensitization was visualized using direct skin testing, plasma anti-soya antibody determination and intestinal myoelectric activity recording. After sensitization, the calves were occasionally fed liquid test meals containing various proportions of antigenic soya and whey. The soya-fed calves displayed larger 24 h skin reactions to beta-conglycinin and higher plasma anti-soya antibody titres than the controls maintained on a skim-milk based milk replacer. Disturbances of the myoelectric activity patterns were recorded on the duodenum and mid-jejunum after feeding antigenic soya, but not non-antigenic soya or milk protein, in the soya-sensitized calves. When the level of antigens was varied, disorders in the jejunal motility patterns appeared when antigenic soya provided one-third or more of the dietary protein in the test meals, although some abnormalities were evident at lower incorporation rates. The major change was a reduction in the mean duration of the jejunal migrating motor complexes which was essentially accounted for by a decrease in the mean duration of the phase I (quiescence). This level of antigens corresponded approximately to 14 and 12 mg of immunoreactive glycinin and beta-conglycinin respectively, per gram of protein intake, i.e. 80 and 70 mg/kg0.75 per test meal.

IgM, IgA, IgG1 and IgG2 specific responses in blood and gut secretion of calves fed soyabean products.

Calves fed soya proteins may develop severe gastrointestinal disorders. Whether these are predominantly associated with particular Ig subclasses and (or) dietary proteins remains unclear. Therefore, antibody responses to soyabean protein were analysed by dot- and blot-immunobinding in plasma and intestinal mucous secretions. One-month-old calves were fed for 2.5 months liquid diets based on skim milk powder (SMP) or a mixture (2:3, protein basis) of whey and soyabean products including a low antigenic hydrolysed soya protein isolate (HSPI) and a highly antigenic heated soya flour (HSF). Specific antibodies (Abs) of the main isotypes (IgM, IgA, IgG1, IgG2) were characterised by immunostaining of samples which had been previously incubated with nitrocellulose sheets coated with SMP, HSPI or HSF extracts. Plasma collected before feeding experimental diets showed very little specific Abs. By contrast, 2.5 months later, a three-fold increase (P < 0.05) in IgG1 and IgA titres against HSF antigens was observed in calves fed HSF compared with those fed the control or HSPI diet. IgG1 immunoblotting revealed many protein bands from soya in the molecular range of 22-32 and 38-42 kDa. Immunorecognition of specific proteins from SMP and HSPI remained low and similar among animal groups. Specific IgM, IgA and IgG1 titres against HSF, and to a lesser extent HSPI, were significantly higher (P < 0.05) in jejunal mucous secretion of calves fed HSF compared with other groups. Secretions from calves fed HSF bound to many soyabean proteins in the range of 17-23 and 26-38 kDa, with similar patterns for IgA and IgG1. By contrast, only weak bands were found for IgM and IgG2 in all groups of calves. Thus, calves fed antigenic HSF do present specific Abs including IgG1 and IgA isotypes, both systemically and locally. Therefore, IgG1 and (or) IgA rather than IgM and IgG2 Abs may be preferred for assessing the immunogenicity of soyabean products in calves. Interestingly, soyabean immunogenicity was drastically reduced by adequate proteolysis.

B and T lymphocytes are enhanced in the gut of piglets fed heat-treated soyabean proteins.

Gut immune responses have been suspected in food hypersensitivity reactions such as those to soyabean proteins in early-weaned piglets. The present study examines the lymphoid cell subset distribution in piglets fed heat-treated (HTSP) or ethanol-treated soyabean proteins (ETSP). Duodenal cryosections of 4-week-old HTSP piglets (n = 10) and ETSP piglets (n = 8) were analysed for IgA, IgM, IgG1 and IgG2 positive cells, CD2, CD4, CD8, WC1 T cell positive antigens using immunohistochemical peroxidase reactions. Densities of IgM+ and IgA+ cells were three times and, IgG1+ and IgG2+ six times higher in the lamina propria of HTSP piglets compared with ETSP (P < 0.05). Increased CD2+ T cells were accounted for by a rise in both CD4+ and CD8+ T cell subsets in the lamina propria (P < 0.01) as well as in the epithelium of the duodenal mucosa of piglets fed HTSP. The density of the WC1+ T cell subset in the epithelium was significantly higher in HTSP than in ETSP piglets (P < 0.01). Immune reactions in the duodenal mucosa, involving both B and T lymphocytes may be related to atrophy of the duodenal villi in HTSP piglets.

Systemic and local gut-specific antibody responses in preruminant calves sensitive to soya.

The systemic and local (gut) patterns of antibodies against various proteins from soyabean were analysed in preruminant calves fed milk substitutes based on skim milk powder (SMP) or heated soyabean flour (HSF) as the main protein sources. The titres of IgM, IgA, IgG1 and IgG2 antibodies were determined against feed extracts and purified soyabean proteins by dot-blotting in plasma after three months and jejunal mucous secretions after six months of feeding the experimental diets. The calves fed HSF had higher levels of circulating IgA, IgG1 and IgG2 antibodies against raw or heated soya extracts and purified proteins including alpha-conglycinin, beta-conglycinin, Bowman-Birk protease inhibitors and lectins than the calves fed SMP. In contrast, the differences between the IgM titres of the groups were most often not significant. The patterns of specific antibodies present in the jejunum were broadly similar to those observed in the blood, although the differences between the groups of calves more often reached significance for IgG2 and IgM than for IgA and IgG1, when the purified soyabean proteins were considered.

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.

Hydrolyzed soy protein isolate sustains high nutritional performance in veal calves.

Milk replacers containing skim milk powder or a mixture of whey and soy protein provided by a hydrolyzed soy protein isolate or a heated soybean flour were fed to 1-mo-old calves for 101 d. The isolate and the flour provided 56 and 72% of dietary proteins, respectively. Digestibility of feed constituents was measured between 9 to 14 d and 65 to 70 d of treatment. Digestive function was evaluated by measurement of ruminal pH, plasma kinetics of triglyceride and glucose concentrations, and xylose absorption. Antibody production was also recorded. Growth and carcass characteristics were satisfactory for the control diet and the diet based on soy isolate, partly because of high apparent digestibility of protein and lack of antibody synthesis in response to soy isolate. In contrast, protein from soybean flour was poorly digested and highly immunogenic. Ruminal pH at 2.5 h after the meal was unaffected by dietary treatments. Postprandial changes in concentrations of triglycerides and glucose in plasma suggested a lack of abomasal clotting with both diets based on soy. Xylose concentration in plasma was only slightly affected by dietary treatment and calf age. Hydrolyzed soy protein is suitable for veal calves and can account for at least half of protein intake.