Deterioration of the environment in which piglets are housed after weaning induces a moderate inflammatory response and modifies tryptophan (Trp) metabolism that can, in turn, decrease Trp availability for growth. We hypothesised that a Trp supply above the current recommendations may be required to preserve Trp availability and to maximise the growth of pigs suffering from moderate inflammation. The aim of this experiment was to compare growth performance and plasma concentrations of Trp and some of its metabolites in piglets, suffering or not from moderate inflammation, when they were fed diets containing graded levels of standardised ileal digestible (SID) Trp, obtained with the addition of crystalline l-Trp to the same basal diet (15%, 18%, 21% or 24%, relative to SID lysine). Differences in inflammatory status were obtained by housing the pigs under different sanitary conditions. Forty blocks of four littermate piglets each were selected and weaned at 4 weeks of age. The experimental design consisted of a split plot where the housing conditions (moderate inflammation v. control) were used as the main plot and dietary Trp content as the subplot. Body weight gain and feed intake were recorded 3, 5 and 7 weeks after weaning. Blood was sampled 13, 36 and 43 days after weaning to measure plasma concentrations of Trp, kynurenine and nicotinamide (i.e. two metabolites of Trp catabolism) and haptoglobin, a major acute phase protein in pigs. There was no interaction between dietary Trp and inflammatory status, irrespective of the response criterion. Compared with control pigs, pigs housed in poor housing conditions consumed less feed (P < 0.0001), had a lower growth rate (P < 0.001), higher plasma concentrations of haptoglobin (P < 0.05) and lower concentrations of plasma Trp irrespective of the Trp content in the diet. Increasing the Trp content in the diet improved feed intake (P < 0.05), growth rate and feed/gain (P < 0.05), but did not prevent the deterioration of performance induced by moderate inflammation because of poor housing conditions. The results of this study suggest that an inflammatory response caused by poor housing sanitary conditions altered Trp metabolism and growth performance, but this was not prevented by additional dietary crystalline l-Trp.

The aim of this experiment was to investigate whether insulin resistance is related to the dietary concentration of Trp and the ADFI of primiparous sows having similar body conditions. Twenty-four primiparous sows were catheterized on d 97 of pregnancy. Blood samples were collected during 3 tests: after the ingestion of 1.5 kg of feed (meal test), after the intravenous infusion of 0.5 g of glucose/kg of BW (glucose tolerance test), and during an euglycemic hyperinsulinemic clamp with an infusion rate of 100 ng of insulin x kg of BW(-1) x min(-1). Both tests were performed at 4 stages at approximately d 103 and 110 of pregnancy and at d 3 and 10 of lactation. Sows were fed a diet containing 0.16 or 0.26% of total Trp (suboptimal vs. slight excessive Trp supply according to recommendations for lactating sows) from d 104 of pregnancy after the first clamp until weaning. The dietary treatment did not result in differences in ADFI, BW, and backfat changes, and growth of piglets during lactation. Plasma Trp concentration was greater for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet (P < 0.05). Plasma glucose, NEFA, and urea profiles during the meal tests were not affected by the dietary treatment. At d 3 of lactation, the insulin concentration at 105 (P = 0.03) and 120 min (P = 0.04) after meal intake was less for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet. On d 10 of lactation, the glucose half life (P = 0.03) and the time needed to reach 25% of the area under the insulin curve (P = 0.04) during the tolerance test were less for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet. The glucose infusion rate during euglycemic hyperinsulinemic clamps was similar in the 2 Trp groups of sows. Irrespective of the dietary treatment, the ADFI of the sows was negatively related to the glucose half life during the glucose tolerance test and positively related to the glucose infusion rate during the clamp (P < 0.05). This relationship observed with the tests performed during early lactation was already found with the tests performed during late pregnancy (P < 0.02). Present findings indicate that a dietary Trp supply of 0.26% does not increase feed intake in lactating primiparous sows. This result indicates that the interest in a Trp supplementation during the peripartum period can be questioned. Irrespective of the dietary treatment, the reasons why sows with similar rearing conditions develop different rates of insulin resistance during pregnancy remain to be elucidated.

Health degradation modifies Trp metabolism through induction of Trp catabolism. This could limit the amount of Trp available for growth. The aims of the present experiment were to investigate the effects of a low grade inflammation and dietary Trp on growth and Trp metabolism. Eighty weaned pigs were assigned to 4 experimental treatments according to a 2 x 2 factorial arrangement: 2 sanitary statuses x 2 dietary Trp contents. The Trp content was deficient (low-Trp: 2.4 and 1.9 g of Trp/kg of the phase I and phase II diets, respectively) or adequate (high-Trp: 2.9 and 2.4 g of Trp/kg of the phase I and phase II diets, respectively). A low grade inflammatory response was induced by housing pigs in unsanitary environment, whereas control pigs were housed in good sanitary conditions. Pigs were not fed ad libitum to avoid feed refusals. Growth performance was calculated 3, 5, and 7 wk after weaning. Blood was sampled 12, 33, and 47 d after weaning for the determination of plasma concentrations of Trp and related metabolites, kynurenine and pyridoxal-5-phosphate. The interaction between sanitary status and dietary Trp was not statistically significant in all measured criteria. Pigs kept in poor sanitary conditions grew slower (P < 0.001) during the entire experimental period and had greater plasma concentrations of haptoglobin (P < 0.001) than pigs housed in good sanitary conditions. Pigs housed in poor sanitary conditions had also decreased Trp plasma concentrations (P < 0.001), but plasma kynurenine concentrations were not affected. Our results indicated that a moderate inflammatory response was obtained by degrading the sanitary quality of environment. Additionally, poor sanitary conditions modified Trp metabolism, indicating that the amount of Trp available for growth and other metabolic functions might be reduced.

The aim of this study was to investigate the cause of variation in the digestibility of pea protein in poultry and to find a tool to select genotypes with high digestibility potential by using an in vitro hydrolysis assay. Eight pea genotypes were selected for their difference in seed protein content and composition. To reduce the variation due to tannins and particle size, seeds from these 8 genotypes were dehulled and micro-ground. They were incorporated as the only protein source in 8 different experimental isoproteinaceous diets with similar metabolisable energy content. The amino acid digestibility was studied in cecectomized chickens. A balance method was used to obtain apparent digestibility, and the isotope dilution technique was used to determine endogenous losses and true digestibility, after feeding a double labelled test meal containing chromic oxide and N-15-labelled peas. The 8 diets showed differences in apparent amino acid digestibility. The average apparent digestibility for all amino acids varied between 79.5 and 86.3%, with the highest values for arginine (85.2 to 90.8%) and glutamic acid (85.2 to 90.5%), and the lowest values for cystine (63.3 to 69.7%) and tryptophan (69.1 to 80.3%). This variability of apparent amino acid digestibility was due to variations in endogenous losses and true digestibility among the 8 pea genotypes. The average endogenous losses as determined for 9 amino acids ranged from 3.6 to 5.4% of ingested amino acids, with the highest value for threonine (8.0 to 11.0%). The average true digestibility varied between 84.4 and 90.2%, with the highest values for lysine (89.0 to 95.0%), and the lowest for isoleucine (81.0 to 88.7%) and valine (82.4 to 88.7%). In vitro hydrolysis of protein from micro-ground seeds was performed for the 8 pea genotypes using three proteases (pepsin, trypsin and chymotrypsin). The quantity of small peptides (<3 kDa) that appeared after the combined hydrolysis with pepsin (3 h) followed by trypsin and chymotrypsin (15 min) was significantly correlated with the average true digestibility of the 8 genotypes (R = 0.74; P<0.05). (C) 2007 Elsevier B.V. All rights reserved.

Voluntary feed intake in sows after parturition may be related to the capacity of the sow to cope with the numerous changes occurring around farrowing. This experiment was undertaken to investigate whether the feed intake during lactation was related to the reactivity of the sow during gestation and plasma Trp and cortisol concentrations. On d 58 of pregnancy, 37 sows were individually placed in a novel environment, and their behavior was observed during a 5-min open-field test. This test allowed the selection of 12 reactive (R) and 8 nonreactive (NR) sows for the study. Sows were fed 3 kg of a standard gestation diet/d before farrowing and a standard lactation diet ad libitum thereafter. The behavioral reactivity of sows when a human touched their neck in the farrowing crate was evaluated on d 72 of gestation, and their behavior during farrowing was analyzed. Sows were catheterized on d 70 of gestation, and blood samples were taken after an overnight fast on d 37 before farrowing, daily during the week before and the week after parturition, and on d 14 and 21 of lactation for plasma Trp and cortisol determination. The NR sows were less reactive to human contact (P=0.02), had a shorter farrowing duration (P=0.02), and tended to have a shorter birth interval between piglets (P=0.09) than the R sows. Feed intake was greater for the NR sows than for the R sows during wk 1 of lactation (P=0.02), as well as during the whole lactation (P=0.03). Plasma cortisol concentration was maximal on the day after farrowing (P=0.01) and returned to basal concentration within 4 d postpartum. No relationship was observed between sow behavior and plasma concentration of cortisol. For both groups of sows, plasma concentrations of Trp between d 2 and 4 postpartum were less than during gestation (P<0.05). The NR sows had decreased plasma Trp concentrations compared with the R sows during wk 1 of lactation (P=0.02). A low reactivity during gestation was associated with behavior of the sow that was favorable to piglet survival during farrowing, increased feed intake, and decreased plasma Trp concentration during wk 1 of lactation. Further research is needed to elucidate whether Trp or Trp metabolites are related to reactivity and ADFI of the reproducing sow.

In pigs, inflammation modifies Trp metabolism and consequently could impact on Trp requirement for growth. In this study, the effects of lung inflammation, induced by the intravenous injection of complete Freund's adjuvant, and dietary Trp content on Trp metabolism and availability were investigated. Two dietary Trp contents, one corresponding to a low-Trp diet (1.5 g of Trp/kg of diet, Basal diet) and the second to an adequate-Trp diet (2 g of Trp/kg of diet, TRP diet), were used. Ten blocks of 4 littermate piglets were selected at 40 d of age. Within each block, piglets were randomly assigned to 1 of the 4 experimental treatments: (1) healthy control and Basal diet, (2) inflammation and Basal diet, (3) inflammation and Basal diet + antioxidant, and (4) inflammation and TRP diet. Inflammation induced an increase in indoleam-ine 2,3 dioxygenase (IDO) activity, an enzyme involved in Trp catabolism, in lung, lymph nodes, heart, and spleen (P < 0.01). Contrary to piglets fed the TRP diet, pigs suffering from inflammation did not maintain their plasma Trp concentrations when they were fed the Basal diet. Furthermore, pigs fed the TRP diet had decreased plasma haptoglobin concentrations, IDO activity, and lung weight than those fed the Basal diet, indicating that the inflammatory response was moderated with the greater Trp supply. Antioxidant addition in the Basal diet decreased the effects of inflammation on plasma Trp concentrations and IDO activity. These results indicated that inflammation increases Trp catabolism and thus may decrease Trp availability for growth.

Mucus plays an important role in gut health by favouring colonisation resistance. The aim of this study was to quantify the impact of fibre and protein on mucin recovery in ileal digesta and on goblet cell histochernistry in the proximal colon. A control diet with highly digestible protein and low fibre and three complex diets containing indigestible protein associated with low, soluble or insoluble fibre sources were tested for 14 days in piglets weaned at 28 days of age. Mucin concentration was determined by ethanol precipitation. Goblet cell subtypes in colonic crypts were analysed by histochernistry. The ileal mucin output was higher with the complex diets than with the control diet (31.6 on average vs 21.7 g/kg DM intake). Increases observed with the low and soluble fibre diets were similar (34 g/kg DM intake). This suggests a limited effect of soluble fibre in presence of indigestible protein. Surprisingly, the observed increase was lower with insoluble fibre (27.2 g/kg DM intake). DM and N output and digestibility were not affected by the diets, but a linear relationship was found between DM and mucin output. In proximal colon, crypt depth, goblet cell numbers per crypt and glycosylation subtypes were not affected by the diet suggesting no change in the capacity of mucus to protect the gut. To conclude, introducing highly indigestible protein in the diet increased ileal mucin output, without effects of these factors on crypt goblet cell patterns in the proximal colon. Introducing fibre in a diet containing highly indigestible protein had a marginal effect. (c) 2007 Elsevier B.V All rights reserved.

The purpose of the current experiment was to investigate the impacts of grinding and pelleting procedures applied to wheat in a wheat–rapeseed meal diet on the coefficients of standardized ileal digestibility, i.e., apparent digestibility corrected for basal endogenous losses (CSID), and true ileal digestibility, i.e., apparent digestibility corrected for total endogenous losses (CTID), of nitrogen (N) and amino acids (AA) in pigs. Ileal digestibility was measured by collecting digesta from pigs fitted with ileorectal anastomoses. Four diets, involving four technological treatments applied to wheat, were compared in vivo according to a 4×4 Latin square design (four pigs each fed four diets during four successive periods of 1 week). The technological treatments of wheat were two grinding procedures and two pelleting processes. Wheat was ground to obtain mean flour particle sizes of 1000 and 500μm, leading after mixing with rapeseed meal and minerals-vitamins premix to the first and second diets named “coarse” and “fine”, respectively. Part of the 500μm wheat flour was pelleted through dies of same screen diameter (4mm) but different thicknesses, 16 and 20mm, inducing a low and high compression ratio, leading after mixing with rapeseed meal and premix to the third and fourth diets named “LCR” and “HCR”, respectively. Basal endogenous losses were determined by feeding a protein-free diet during the 5th week of the experiment. Total endogenous losses were measured by way of the isotopic dilution method using 15N-labeled wheat and rapeseed meal. Decreasing wheat particle size from 1000 to 500μm improved (P<0.05) the coefficient of ileal digestibility of dietary energy (0.707 versus 0.665), organic matter (0.718 versus 0.677) and dry matter (0.681 versus 0.645), but neither AA CSID nor N retention. The pelleting processes did not further increase (P>0.10) energy or organic matter digestibility but improved (P<0.05) N and AA CSID (0.785 versus 0.759 for N and 0.725 versus 0.679 for lysine, with HCR versus fine diet, respectively). Pelleting wheat flour at higher compression ratio (HCR versus LCR diet) was more efficient to improve dietary N and AA digestibility values due to a significant decrease in ileal specific, i.e., total minus basal, N and AA endogenous losses (P<0.05) associated with an increase in CTID. It is concluded that pelleting wheat fine flour at high compression ratio allows maximizing AA digestibility and availability of a wheat–rapeseed meal diet.

In a previous study, a reduced efficiency of ileal digestible threonine (THR) use for body protein deposition was observed in growing pigs when pectin was included in the diet. This response was not due to increased physical endogenous ileal THR loss. Our aim was to explore the contribution of diet-induced increases in protein synthesis in the colon, especially mucins, to dietary THR requirements. Twelve barrows (21 kg mean BW) were fed either a cornstarch–soybean meal-based diet (Control) or Control with 12% pectin (Pectin). Pigs were given intravenously 1.5 mmol/kg BW of L-1-13C valine (40 mol%) to measure fractional and absolute synthesis rates (FSR, ASR, respectively) of mucosal and whole intestinal protein in the jejunum and colon. Dietary pectin inclusion increased plasma levels of glucose, isoleucine and glutamine (P<0.05) but had no effect on insulin or urea nitrogen (P>0.10). There were no differences in FSR and ASR of whole intestinal protein in jejunum and colon (P>0.10). The FSR of mucosal proteins in colon, not in jejunum, was increased with dietary pectin supplementation (P<0.05). Assuming mucosal protein mass is constant, these results imply that the higher protein synthesis in colon mucosa contributes to the reduced THR efficiency observed in pectin-supplemented diet.

Eight pea genotypes characterized for their major protein fractions were used to investigate the effect of seed protein composition variability on protein digestibility in poultry. These genotypes of various pea types, were also variable in other seed components. They showed variations in their carbohydrate (insoluble fibre compounds, soluble fibre, soluble carbohydrates) and trypsin inhibitor (TI) contents. To exclude the effect of tannins and of particle size, the seeds were dehulled and micro-ground. They were incorporated as the only protein source in isoproteinaceous diets with similar metabolisable energy content and fed to cecectomized chickens. The average amino acid digestibility (apparent and true) and endogenous amino acid excretion were related with pea diet characteristics (protein composition, carbohydrate composition and TI activity). This allowed to precise which of the diet characteristics affect protein digestibility and endogenous excretion. Average apparent digestibility of amino acids was negatively correlated with insoluble fibre components (R=−0.71 to −0.72; p<0.05) and TI activity (R=−0.93; p<0.001). Average endogenous losses of amino acids were positively correlated with soluble carbohydrate content (R=0.77; p<0.05) and TI activity (R=0.84; p<0.01). Average true digestibility of amino acids was positively correlated with the PA2 albumin level (R=0.71; p<0.05), and negatively with the legumin level (R=−0.72; p<0.05). Resistant peptides extracted from chicken excreta were analysed through electrophoresis and identified by immunodetection. Intensity of detected resistant peptides showed variation among genotypes. However, for the 8 pea genotypes, the pea proteins, which persisted at the end of the digestive tract, were mainly albumin PA1b and lectin. Other minor peptides were also detected: vicilin, albumin PA2 and legumin peptides which migrated at the same level as β-subunits.

High dietary threonine extraction by the digestive tract suggests that threonine contributes to maintain gut physiology. The aims of this study were to investigate both the physiological disturbances and the molecular events caused by an inadequate dietary threonine supply to the ileum of piglets. We compared paracellular permeability and gene expression, using porcine cDNA microarrays, of the ileum of piglets weaned at 7 days of age fed either a low (LT; n=7) or a control (C; n=7) well balanced threonine diet for 2 weeks. At slaughter, the ileal paracellular permeability, measured by FD4 flux in Ussing chambers, increased in piglets fed a LT diet compared with C piglets (P=0.017). Furthermore, 170 genes had their expression significantly modified in the ileum of the LT piglets: 64 were down regulated and 106 were up regulated. These genes are involved in immune response, apoptosis, energy metabolism, cell migration, epithelial permeability, RNA processing or protein translation. In conclusion, dietary threonine deficiency induced alteration of the ileal barrier and the ileum seems to respond by increasing its metabolic activity. (c) 2007 Elsevier B.V. All rights reserved.

Measures of ileal digestibility (ID) are used routinely as estimates of amino acid (AA) bio-availability in pig feed ingredients. Values for ID may be expressed as apparent (AID), standardized (SID), or true (TID). Values for AID are calculated by deducting the total ileal outflow of AA (the sum of endogenous losses (IAAend) and non-digested dietary AA) from dietary AA intake. The IAAend may be separated into basal losses, which are not influenced by feed ingredient composition, and specific losses induced by feed ingredient characteristics such as anti-nutritional factors and dietary fiber. If the AID values are corrected for total IAAend, then values for TID are calculated. Lack of additivity of AID values in feed formulation may be overcome by correcting AID values for basal IAAend only, which yields SID values. Until reliable procedures for the routine measurement of specific IAAend become available, it is suggested that SID values are used for feed formulation. It is advisable that basal IAAend are measured in digestibility experiments and that these losses are reported with SID values.