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In pigs the extensive threonine utilization by the splanchnic tissues explains the relative inefficiency of dietary threonine conversion for body protein accretion. Two experiments were conducted to estimate the contribution of the portal drained viscera (PDV) and the liver to threonine metabolism and especially catabolism in growing pigs. In the first experiment, four pigs were surgically prepared for chronic catheter insertion in the portal, hepatic and jugular veins and in the carotid artery. They were continuously infused with L-[1-(13)C]threonine through the jugular catheter. The PDV and total splanchnic viscera (PDV and the liver) extracted 14.3 and 18.8% of arterial threonine input, respectively. In a second experiment, we studied the metabolism of dietary threonine in the PDV and the liver in six female growing pigs. Animals were surgically prepared as in the first experiment except that L-[1-(13)C]threonine and [(15)N]glycine were continuously infused in the duodenum for 10 h. Unlabelled and labelled threonine and glycine PDV, liver and splanchnic tissues balance were calculated from plasma samples taken during the last 2 h of this infusion. Splanchnic tissues extracted 60% of infused labelled threonine, 88% of which was extracted by PDV so that threonine extraction by the liver was low. Both the liver and the pancreas can degrade threonine through the L-threonine 3-dehydrogenase pathway but not the intestine. Our data suggest that threonine catabolism through the L-threonine 3-dehydrogenase pathway was only a minor component of total threonine utilization in the splanchnic tissues.

In a preliminary study we observed that piglets suffering from chronic lung inflammation induced by an intravenous injection of complete Freund adjuvant showed a marked decrease in plasma tryptophan (Trp) concentration suggesting increased Trp utilisation. During the inflammatory process, a cytokine-induced enzyme called indoleamine 2,3-dioxygenase (IDO) has been shown to catabolise Trp into kynurenine (Kyn). Yet, during inflammation, increased Trp catabolism may decrease Trp availability for other functions such as growth. This metabolic pathway has never been studied in pigs. So, the objectives of this study were to measure IDO activity in pigs and to determine if the decrease in plasma Trp concentrations previously observed in piglets suffering from chronic lung inflammation could be explained by the induction of IDO activity. In order to do so, we compared IDO activity measured in the tracheo-bronchial lymph nodes and in the lungs of 7 piglets, injected with complete Freund adjuvant (CFA), to 7 pair-fed littermate healthy controls. Blood samples were taken at 0, 2, 5, 7 and 10 days following CFA injection in order to measure plasma Trp, Kyn and haptoglobin concentrations. Indoleamine 2,3-dioygenase activity in the tracheo-bronchial lymph nodes (P < 0.05), in the lungs (P < 0.07) and plasma haptoglobin (P < 0.01) were higher in pigs with lung inflammation than in the controls. Plasma Trp and Kyn were not significantly affected by CFA injection. Our data showed that IDO is activated under chronic lung inflammation in pigs. The impact of IDO activation on plasma Trp concentration and its availability is discussed according to the amount of Trp provided by the diet.

Intestinal mucin, a family of glycoproteins secreted by goblet cells, is the main constituent of the mucus protecting the gastrointestinal tract. For optimal mucosal protection, both the quantitative and qualitative characteristics of mucin are essential. To evaluate how viscosity influences ileal apparent digestibility and mucin biology, a highly viscous nonfermentable soluble polysaccharide, carboxymethylcellulose (CMC), was fed to weaned piglets for 15 d. The ileal crude mucin concentration was determined by ethanol precipitation, and changes in goblet cell subtypes were analyzed by the histochemistry of ileal and colonic tissues. As expected, CMC increased the viscosity of ileal digesta and the moisture of feces (P < 0.001). The crude mucin concentration and output at the ileum were higher (P < 0.05) in pigs fed CMC than those fed the control diet. Increasing intestinal content viscosity in pigs fed CMC had no significant effects on the ileal apparent digestibility of dry matter, organic matter, nitrogen, and minerals. The number of total ileal goblet cells per villus also was higher (+30%, P < 0.05) in pigs fed the CMC diet compared with controls. This increase was essentially accounted for by increased numbers of acidic and acidic sulfated mucin-containing cells (+30%, P < 0.05). Trends (P = 0.06) toward decreased numbers of neutral and acidic mucin-containing cells in ileal crypts were also noted. In conclusion, increasing intestinal content viscosity in weaned piglets fed CMC increased the ileal mucin output and numbers and maturation of goblet cells in ileal villi without effects on the apparent digestibility of the diet.

This study investigated intestinal physiology of piglets at weaning. Piglets (n = 60) weaned at 21 d were food deprived for 2 d and then tube-fed using 2 different diets (a conventional diet vs. a wheat-enriched diet). They were slaughtered at d 0, 2, 5, 8, or 15 postweaning. Jejunum, ileum, and colon were mounted in Ussing chambers. In addition, segments of the proximal jejunum of 4 growing pigs were studied 35 d after weaning. Secretory function was assessed by basal short-circuit current (Isc) and secretagogue-stimulated Isc. Glucose absorption was measured by the increase in Isc after the addition of glucose. Epithelial barrier function was measured by transmucosal resistance (R) and horseradish peroxidase (HRP) fluxes across the epithelium. There were no significant differences between the pigs fed the 2 diets for any of the parameters studied. As already reported, a transient villous atrophy was observed. At the same time, we observed an increased basal Isc in jejunum and colon, increased glucose absorption and a dramatic drop of R in jejunum. These parameters had returned to preweaning values by d 5. Weaning was also followed by long-lasting modifications. In jejunum, responses to the secretagogues and glucose absorption were decreased at wk 2 after weaning and were not different between d 15 and 35. Ileal transmucosal resistance increased on d 5 and was stable thereafter. HRP flux in jejunum declined on d 2 and stayed at this low level throughout the experiment. We conclude that weaning induces transient dramatic changes in intestinal physiology but is also a period of maturation of the intestine.

A fundamental question in animal nutrition is the amino acid requirement induced by inflammation and immune response. The aim of the present experiment was to study the effect of chronic lung inflammation induced by injection of complete Freund adjuvant on amino acid metabolism in pigs. For 10 days, we compared plasma haptoglobine and amino acid concentrations of piglets with chronic lung inflammation (CFA) with those of pair-fed littermate healthy pigs (CONTROL). Tryptophan was the only amino acid for which the plasma concentration was continously decreasing and did not reach the control level at the end of the experimental period. We suggested that an increase in tryptophan catabolism under indoleamine 2, 3 dioxygenase activation and/or tryptophan incorporation into acute phase protein could explained the decrease in plasma tryptophan concentration in pigs suffuring from chronic lung inflammation.

The vagus is involved in the cephalic phase of insulin secretion but its role in the meal absorption phase of insulin release remains to be defined. The aim of this study was therefore to evaluate the role of the vagus in the early and the late meal absorption phases of insulin secretion. In six pigs, venous insulin profiles were compared in intact animals, after ventral or dorsal vagal trunk section, and after section of both vagal trunks (truncal vagotomy). Since gastric emptying could be modified by vagotomy, it was recorded concomitantly by gamma scintigraphy. Semi-solid (porridge) and liquid (glucose 10%) meals were tested. Truncal vagotomy significantly increased insulin release compare to intact animals after glucose (63.8%) and porridge (174.4%) meals in the early and the late absorption phases of insulin secretion, respectively. For the glucose meal, this effect could be explained by a vagally mediated change in gastric emptying rate, since insulin concentrations for a similar amount of nutrient propelled to the duodenum were not different in intact and truncal vagotomized animals. In contrast, after the porridge meal, truncal vagotomy was associated with a second, later occurring increase in circulating insulin, which could not be explained by changes in gastric emptying rate. These results demonstrate for the first time an inhibitory role of the vagus in the late meal absorption phase of insulin release.

Background: Incidence of diarrhea at weaning in commercial pigs is an important problem, and diet is thought to be a predisposing factor. The aim of this study was to determine the impact of switching from milk-based to cereal-based diets on the morphology and function of the small intestine of piglets using a model of delayed weaning to isolate the influence of the diet from that of environmental and social factors., Methods: Forty-five piglets received a milk-based diet for 5 weeks after weaning. Thirty piglets were then switched from milk-based to wheat- or barley-based diets, mimicking the dietary change that occurs at weaning. The last 15 piglets remained on the milk-based diet. Piglets were killed 4 days after the dietary switch. Jejunal mucosa morphometry and enzyme activities were measured. Ussing chambers were used to measure intestinal permeability to macromolecules, basal electrical properties, glucose absorption, and induced chloride-secretion., Results: Alkaline phosphatase- and sucrase-specific activities were higher in both groups of cereal-fed piglets than in milk-fed piglets. Dipeptidylpeptidase IV activity was higher in wheat-fed piglets than in the other groups. Na + -dependent glucose absorption was 1.7-fold higher in cereals-fed piglets than in milk-fed piglets. Serotonin-induced and vasoactive intestinal polypeptide-induced chloride secretion was doubled in cereals-fed piglets. Dietary transition did not influence the other parameters., Conclusions: These results indicate that switching from milk to cereals increased some mucosal enzyme activities, intestinal Na + -dependent glucose absorption, and response to secretagogues. This supports the hypothesis that dietary factors could initiate diarrhea in the presence of other aggravating factors, such as pathogens or environmental stress.

Contributions of erythrocytes and plasma to threonine and lysine transport across the PDV and the liver were determined in growing pigs successively fed a threonine deficient diet and a control well-balanced diet (experiment 1) or a lysine deficient or a well-balanced diet (experiment 2). The animals were surgically prepared for insertion of chronic catheters in the mesenteric vein (MV), the portal vein (PV), a hepatic vein (HV) and the carotid artery (CA). Plasma and whole blood AA concentrations in PV, HV and CA and PV and HV blood flows were determined during 6 hours of para-aminohippuric acid constant infusion. During this period the pigs were continuously fed (1 meal per hour). The contribution of plasma to lysine and threonine transport was higher in pigs fed the well balanced diets. More than 50% of threonine and lysine appearing in the PV and in the HV are transported by the plasma. Our results suggest that erythrocytes are probably little involved in lysine and threonine transfer across the liver and digestive tract of pig continuously fed.

The aims of the present study were first to compare the amino acid dilution method performed using labelled animals with that using labelled diets, and second to determine real digestibilities and total ileal endogenous losses of N and amino acids. Two diets containing pea cultivars (Solara and Amino) and a protein-free diet were compared in a 3 x 3 Latin-square experiment. The three pigs were each prepared with an ileo-rectal anastomosis and were continuously infused with [1-13C]leucine. For each cultivar, 15N-labelled and unlabelled diets were formulated. The real digestibility and endogenous losses of leucine were higher when obtained by labelling the pig than by labelling the foodstuff. This was due either to the inadequate estimation of the endogenous protein enrichment in the first case or to the importance of dietary N recycling in the second case. However, in both cases the ileal endogenous losses of N and amino acids were higher than the basal losses determined with the protein-free diet. There were significant differences between the two pea cultivars in terms of phenylalanine and leucine when measured with labelled diets. It is suggested that, although ileal endogenous losses may be underestimated, using labelled feedstuffs is of great interest due to the direct estimation of the individual amounts of amino acids.

Dairy products provide abundant, accessible calcium for humans, while some calcium sulfate-rich mineral waters could provide appreciable amounts of calcium. But there is little evidence that this calcium is as available as milk calcium for making bone. The availability of calcium was studied by monitoring bone parameters in 2-month-old pigs fed restricted amounts of calcium (70% RDA) for 2.5 months. The 3 main (> or = 50% Ca intake) Ca sources were either CaCO3 or CaSO4 or skim milk powder (29% of the diet). The bones of the pigs fed the "milk" diet had higher (P < 0.01) ash contents, breaking strength and density (DEXA) than those of the two others groups, in which the bone values were similar. Thus, the calcium provided by a diet containing milk appears to ensure better bone mineralization than do calcium salts included in a non-milk diet. The calcium restriction may have enhanced some milk properties to stimulate calcium absorption in these young, rapidly growing pigs.

Whole blood (WB) and plasma (P) amino acid transfers across the portal drained viscera and the liver were determined during 6 h of a constant p-aminohippuric acid infusion in three hourly-fed Landrace x Large-White pigs (30.5 kg, mean live weight) surgically prepared with chronically inserted catheters in a mesenteric vein (MV), the portal vein (PV), an hepatic vein (HV) and the carotid artery (CA). Plasma and WB amino acid concentrations were determined in the CA, PV and HV. The plasma/WB ratios showed no significant differences for vessels except for lysine and glutamate for which this ratio is significantly higher in the HV and in the PV for lysine. This suggests that the PV lysine and HV glutamate were preferentially transported in the plasma. In the PV, threonine, valine and alanine are transported by both plasma and red blood cells. These data show that the contribution of plasma and whole blood to amino acid transport can be different between amino acids and between individual tissues.

Tryptophan (TRP) is shown to play original roles in the physiology of pigs. Dietary TRP deficiency induces depression of the appetite leading to reduced growth performance. Brain hydroxy-indoles, including the neurotransmitter serotonin, are closely related to dietary TRP supply. Excess protein, namely large neutral amino acids (LNAA) enhanced the appetite depression, providing some support to a role for plasma TRP:LNAA in the regulation of protein intake through serotonin. Other implications of TRP, as a precursor for serotonin, in the susceptibility of pigs to stress and in their consequences on meat quality were reported. Furthermore, we concluded to a role for TRP in the insulin response to the meal and in tissue sensitivity to insulin. Implications in pig feeding practice are briefly reviewed.

The authors report 26 cases of female genital schistosomiasis. This parasitosis is observed in women of ages ranging between 17 and 70 years (mean age = 30 years) and associated with sterility (6 cases), uterine tract cancer (1 case), tubular pregnancy (1 case), benign teratoma (1 case) and serous cystadenoma (1 case). The diagnosis is based on an histological analysis which shows several lesions with schistosomiasis (Schistosoma haematobium) eggs, confirmed by ZIEHL coloration. When coupled with infections these anatomical lesions lead to dysfunctions such as sterility and extra-uterine pregnancy through tubular dysfunction.

Two experiments were designed to determine the tissue distribution of threonine oxidation through the threonine dehydrogenase (EC 1.1.1.103) pathway in pigs. The first experiment was conducted on eleven Piétrain x Large White piglets. The piglets were slaughtered at 5, 12 or 20 kg after 1 h of infusion with L-[U-14C]threonine (55 kBq/kg) mixed with unlabelled threonine (100 mg/kg). In the second experiment, four Piétrain x Large White and four large White piglets (10 kg body weight) were infused with L-[1-13C]threonine (50 mg/kg) mixed with 50 mg/kg unlabelled threonine for 1 h, then killed for tissue sampling. In the two experiments, threonine dehydrogenase specific activity and threonine and glycine specific radioactivities and enrichments were measured in several tissues and in plasma. The higher level of labelling of threonine in the pancreas than in the liver suggested either a lower protein degradation rate or a faster rate of threonine transport in the liver than in the pancreas. Threonine dehydrogenase activity was found only in the liver and the pancreas. Whereas liver and pancreas threonine dehydrogenase specific activities were similar, glycine specific radioactivity and enrichment were 12- to 14-fold higher in the pancreas than in the liver. This is probably the consequence of a higher production rate of glycine from sources other than threonine (protein degradation, de novo synthesis from serine) in the liver than in the pancreas. Our results showed that Large White pigs could oxidize more threonine than Piétrain x Large White pigs. This could be related to the difference in growth performance and dietary N efficiency for protein deposition between these two genotypes.

Threonine oxidation was examined in 12 growing pigs fed a well-balanced control diet or a threonine-deficient diet supplemented (Glu) or not (LT) with glutamic acid during constant infusion of L-[1-(13)C]-threonine, [1-(14)C]glycine and [1-(14)C]alpha-ketobutyrate for 10 h. During these infusion, liver glycine enrichment was significantly lower than plasma enrichment. Moreover, the pancreas to plasma glycine enrichment ratio was higher than the liver to plasma ratio (70-89%), showing that an important part of glycine de novo synthesis in pancreas occurred through the threonine dehydrogenase (TDG) pathway. These results imply that calculation of threonine oxidation into glycine should be made with the assumption of both hepatic and extrahepatic oxidation. Plateau values of plasma threonine, glycine and alpha-ketobutyrate enrichments and specific radio activities allowed estimations of threonine oxidation through the TDG and threonine dehydratase (TDH) pathways. Threonine oxidation into glycine was 12.16 +/- 2.06, 2.89 +/- 0.61 and 2.13 +/- 0.44 mumol/(kg.h), respectively, in pigs fed the control, LT and Glu diets, and threonine oxidation into alpha-ketobutyrate was 1.80 +/- 0.31, 0.88 +/- 0.02 and 0.55 +/- 0.06 mumol/ (kg.h) for the control, LT and Glu groups, respectively. Total threonine oxidation rates were 75 and 81% lower in the LT and Glu groups, respectively, than in the control group. Liver TDG and TDH activity measured in vitro were not affected by either the level of dietary threonine supply the addition of glutamic acid. On the basis of plasma data, it may be concluded that the addition of glutamic acid to a threonine-deficient diet had no significant effect on threonine oxidation but did reduce the rate of threonine release from protein breakdown. Oxidation appears to be related to plasma threonine concentration.

The effects of dietary levels of threonine, protein (essential and nonessential amino acids) and glutamic acid (nonessential amino acid) on growth, food intake and threonine metabolism were studied in 54 fattening female pigs (Piétrain x Large White) from 40 to 100 kg live weight. Six experimental diets were compared using a 2 x 3 factorial design: two levels of threonine (0.42 and 0.52 g/100 g) corresponding to a limited and an adequate supply for growth, and three types of nitrogen supply: a basal diet supplying 12.6 g crude protein/100 g, a second diet providing additional protein to give a total supply of 15.6 g crude protein/100 g, and a third diet providing nonessential nitrogen in the form of L-glutamic acid to give the same total supply of 15.6 g crude protein/100 g diet. Protein addition to the basal diets did not modify growth performance but increased L-threonine-3-dehydrogenase (TDG) activity when pigs were fed the higher threonine diet. The addition of L-glutamic acid to the threonine-deficient diet improved growth performance, but there was no effect at the higher level of threonine. Glutamic acid increased TDG activity in pigs fed the low threonine diet. We conclude that glutamic acid may have a sparing effect on threonine when threonine is rate-limiting for protein deposition, but the mechanism of the interaction between the two amino acids remains unknown.

The present experiment was designed to study the influence of dietary energy source (fat or carbohydrate) and tryptophan (TRP) on protein synthesis and plasma insulin concentrations in the piglet. Six dietary regimens, based on either a high-fat (F) or a high-carbohydrate (C) diet with three levels of TRP (deficient, 1; adequate, 2; excess, 3), were used. Fractional protein synthesis rate (ks; % per d) was measured in the liver, Longissimus dorsi (LD), Semitendinosus (ST), skin, femur, brain, pancreas, stomach, mucosa of the duodenum and jejunum, and the whole body, using a 'flooding dose' of 3H-phenylalanine. Mean integrated insulin, gastric inhibitory polypeptide (GIP) and glucose concentrations were higher after the C diets compared with the F diets, TRP supplementation globally augmented ks linearly in the liver, ST, skin and whole body, while it had quadratic effects in the LD (ks highest in the TRP-adequate diet groups) and jejunal mucosa (ks lowest in the TRP-adequate diet groups). Pancreatic ks was increased by TRP addition up to a plateau. Ks was highest after the F diets in the digestive tissues while in the skin and LD ks was highest after the C diets. Fasting concentrations of gluconeogenic amino acids were lower (and urea higher) with the F than the C diets, suggesting their use as precursors for glucose synthesis. In conclusion, we have confirmed the depressive effects of TRP deficiency on ks, RNA activity and growth. We could not establish a relationship between plasma insulin and muscle ks. This may be related to the way in which we manipulated plasma insulin concentrations.

The aim of this experiment was to investigate the influence of oral tryptophan on insulin, glucose-mediated insulinotropic polypeptide and glucose concentrations in early-weaned piglets. Piglets were given by intragastric infusion, at the same level of feeding, either a tryptophan-deficient or tryptophan-adequate diet for 22 d. During the experiment blood samples were taken after intragastric infusion of 1) the accustomed meal, 2) a glucose plus tryptophan load and 3) a glucose load. Plasma samples were analyzed for insulin, glucose-mediated insulinotropic polypeptide, glucose and lactate. After the accustomed meal plasma insulin concentrations were augmented and liquid gastric emptying faster in pigs fed tryptophan-adequate compared with tryptophan-deficient diets (P < 0.05) but glucose-mediated insulinotropic polypeptide, glucose and lactate were unaffected. The addition of tryptophan to a glucose load increased glucose-mediated insulinotropic polypeptide and reduced glucose in both tryptophan-adequate and tryptophan-deficient diet fed pigs (P < 0.05). Piglets adapted to the tryptophan-adequate diet had a greater glucose-mediated insulinotropic polypeptide response to intragastric glucose plus tryptophan than piglets adapted to the tryptophan-deficient diet. Adaptation to a tryptophan-adequate diet seems to increase the release of glucose-mediated insulinotropic polypeptide due to infusion of a tryptophan-adequate compared with a tryptophan-deficient diet. The addition of tryptophan to a glucose load reduces the level of glycemia, possibly through glucose-mediated insulinotropic polypeptide-mediated glucose disposal.

The effects of a daily porcine somatotropin injection on protein synthesis rate in muscle (longissimus), liver and intestine, as influenced by dietary protein, were investigated in 17 pigs. The measurements were made at wk 3 of treatment following 1 wk for adaptation to the diet and 1 wk for determination of nitrogen balance. The fractional rates of protein synthesis in the muscle, liver and intestine were measured using a flooding dose of L-[1-13C]valine. Positive responses of weight gain and nitrogen balance were observed, primarily at higher dietary protein intake, after porcine somatotropin treatment. As expected, porcine somatotropin-treated pigs had a higher proportion of muscle and less fat. Fractional protein synthesis rate was 16% higher in the liver of porcine somatotropin-treated pigs (P < 0.05). In the longissimus muscle fractional protein synthesis rate increased with porcine somatotropin dose from 3.2 to 3.7%/d and from 4.1 to 5.1%/d at low and high protein intake, respectively (P < 0.05). The effect of dietary protein on fractional protein synthesis rate in longissimus was significant, but there was no porcine somatotropin x protein interaction. Ribonucleic acid concentration followed the same pattern as fractional protein synthesis rate in liver and longissimus. In the duodenal tissue, porcine somatotropin treatment depressed fractional protein synthesis rate (P < 0.05) without an effect of dietary protein and RNA concentration did not change. In porcine somatotropin compared with placebo-treated pigs, plasma glucose, insulin and insulin-like growth factor-I concentrations were elevated whereas plasma thyroxine was depressed and plasma triiodothyronine remained constant. There was no clear effect of dietary protein on plasma hormones. We concluded that, in pigs fed an adequate level of protein, porcine somatotropin stimulates protein synthesis in the liver and the muscle, primarily through increased ribosomal capacity.