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Cytokines play a central role in immune cell response, but they also participate in the maintenance of tissue integrity. Changes in the cytokine network of the pig gut may be expected at weaning, because abrupt changes in dietary and environmental factors lead to important morphological and functional adaptations in the gut. This study measured the gene expression of 6 inflammatory cytokines along the small intestine (SI) and the proximal colon in 28-d-old piglets (n = 45) at different time points (0, 1, 2, 5 and 8 d) postweaning, using RT-PCR. Villus-crypt architecture and enzymatic activities of lactase and sucrase in the SI were also examined. The results confirmed that weaning is associated with morphological and enzymatic changes in the SI. In addition, the data indicated that cytokine response in the gut could be divided into two periods: an early acute response (0 to 2 d postweaning) and a late long-lasting response (2 to 8 d postweaning). Between d 0 and d 2, the levels of IL-1beta, IL-6, and TNF-alpha messenger RNA (mRNA) increased. Marked upregulation of IL-1beta mRNA occurred in most parts of the intestine, whereas IL-6 and TNF-alpha mRNA markedly increased only at specific sites in the intestine. Between d 2 and d 8, the levels of IL-1beta, IL-6, and TNF-alpha mRNA rapidly returned to preweaning values, except that the level of TNF-alpha mRNA remained high in the distal SI. Levels of IL-12 subunit p40 (IL-12p40) and IL-18 mRNA also decreased, compared to those on d 0. Taken together, these results demonstrate that weaning in piglets is associated with an early and transient response in gene expression of inflammatory cytokines in the gut. [ABSTRACT FROM AUTHOR]

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/kg of BW-1·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 mill (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. [ABSTRACT FROM AUTHOR]

ABSTRACT: 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. [ABSTRACT FROM AUTHOR]

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 indoleamme 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. [ABSTRACT FROM AUTHOR]

A study was conducted to investigate the biochemistry of digestion of field pea (Pisum sativum L.) albumins and globulins in the stomach and along the small intestine of weaned piglets with a particular emphasis on the respective roles of these compartments in pea protein digestion. Twenty-four piglets were weaned at 28 d of age. They were allocated to 2 diets (control and pea) and 3 slaughter times (3, 6, or 9 h after the last meal) in a 2 x 3 factorial arrangement of treatments in a randomized complete block design. Pea flour provided 30% of total dietary protein in the pea diet. The diets were fed for 2 wk after weaning. After slaughter, gastrointestinal tract (GIT) compartments were weighed, digesta were collected, and pH was measured. Digesta from the stomach and cranial, middle, and caudal small intestine (SI) were extracted for soluble proteins and analyzed for specific pea proteins using SDS-PAGE, immunoblotting, and mass spectrometry. Tissue weight of the whole GIT (P = 0.015), cecum (P < 0.001), and colon (P < 0.001) was greater in the pea diet. Digesta pH in the stomach and caudal SI was lower (P = 0.02) in the pea diet than the control diet. In the stomach, vicilin, lectin, and pea albumin 2 were not digested, whereas legumin was only partly digested. Legumin and vicilin were totally digested in the SI in less than 3 h. A resistant peptide of 15 kDa located at the N-terminus of pea albumin 2 was transiently detected at 3 h. A protein band at 20 kDa was consistently identified as lectin. It was present in high intensity in intestinal digesta of pea-fed piglets at all times after the meal compared with those fed the control diet (P < 0.001). Various proteins of, presumably, endogenous origin displayed differential digestion patterns between the control and the pea-fed piglets (P <0.05). In conclusion, differences in digestion between specific pea proteins were observed along the GIT of piglets. They could be partly explained by differences in protein digestion in the stomach. [ABSTRACT FROM AUTHOR]

In this review, the terminology that is used to describe the bioavailability and ileal digestibility of AA in pig feed ingredients is defined. Aspects of the methodology to establish bioavailability and ileal digestibility values also are discussed, and recommendations about the use of these values are provided. Two main factors can contribute to differences between bio-availability and ileal digestibility of AA. First, some AA, such as Lys, may be absorbed in chemical complexes that preclude their use for metabolism. Second, fermentation in the upper gut may result in a net loss or gain of AA to the animal. In addition, dietary effects on the efficiency of using bioavailable AA intake for tissue growth or milk production should be considered and may be attributed to endogenous AA losses in the hindgut and the metabolic costs associated with endogenous gut protein synthesis and losses. Ileal digestibility values may be expressed as apparent ileal digestibility (AID), standardized ileal digestibility (SID), or true ileal digestibility (TID). These terms are used to specify how ileal endogenous AA losses are reflected in digestibility values. Ileal endogenous AA losses may be separated into basal losses, which are not influenced by feed ingredient composition, and specific losses, which are induced by feed ingredient characteristics such as levels and types of fiber and antinutritional factors. Values for AID are established when total ileal outflow of AA (i.e., the sum of endogenous losses and nondigested dietary AA) is related to dietary AA intake. A concern with the use of AID values is that these are not additive in mixtures of feed ingredients. This concern may be overcome by correcting AID values for defined basal endogenous losses of AA, which yields SID values. Furthermore, if the AID values are corrected for basal and specific endogenous losses, then values for TID are calculated. However, reliable procedures to routinely measure specific endogenous losses are not yet available. It is recommended that basal ileal endogenous losses of AA should be measured in digestibility experiments using a defined protein-free diet and that these losses are reported with observed AID and SID values. It is suggested that SID values should be used for feed formulation, at least until more information on TID values becomes available. [ABSTRACT FROM AUTHOR]

Metabolic changes associated with inflammatory processes and immune response can modify protein and AA requirements. Improved knowledge of these processes will provide opportunities for nutritional intervention to sustain growth and animal defense at the same time. The objective of the study was to identify AA whose metabolism is affected by chronic lung inflammation. Six pairs of littermate piglets were selected at 28 d of age on the basis of their BW. After catheterization of the jugular vein, one littermate received complete Freund's adjuvant (CFA) intravenously, whereas its littermate was injected with a sterile saline solution (CON). Piglets within a litter were pair-fed in order to avoid confounding effects of feed intake and inflammation on plasma AA concentrations. Blood samples were taken after an overnight fast and 2 h after the morning meal for 9 d. Rectal temperature, food consumption, weight gain, plasma haptoglobin, and AA concentrations were measured. The CFA injection decreased food intake, and increased body tempera- ture and plasma haptoglobin concentration. Plasma tryptophan, glutamine, proline, glycine, tyrosine, omithine, total AA concentrations, and the ratio of tryptophan to large neutral AA were less in CFA than in CON (P < 0.05), independent of time and meal. In contrast, plasma histidine concentration was higher (P < 0.05) in CFA than in CON pigs. Plasma serine, arginine, alanine, asparagine, and total AA concentrations were lower in CFA than in CON pigs only in the fed state (P < 0.05). Among essential AA, only plasma tryptophan concentration was lower (P < 0.01) in CFA than in CON pigs in both fasted and fed state. These results show that chronic lung inflammation affects individual AA differently and suggest that the utilization of some AA increased during chronic lung inflammation in pigs. Activation of tryptophan catabolism enzyme indoleamine 2,3-dioxygenase seems a relevant hypothesis to explain the increased tryptophan utilization, although its incorporation in acute-phase proteins and the existence of other catabolic pathways cannot be excluded. [ABSTRACT FROM AUTHOR]

The current 15N-leucine infusion technique may overestimate the ileal endogenous nitrogen losses in pigs. To determine the reason, we infused four cannulated pigs intravenously, fed them a pea-based diet with 15N-leucine, and examined some methodological variables. Neither the blood sampling time nor the choice of precursor pool (total N or amino acid N of deproteinized plasma) or the method of estimation of the isotopic equilibrium level significantly affected the results. On the other hand, the 15N-enrichment of purified mucin, isolated from ileal digesta, was higher than that of the plasma amino acid pool (0.114 vs. 0.077 atom % excess). The endogenous proportion of the labeled amino acids (Ala, Gly, Ile, Leu and Val) in the ileal digesta ranged from 23 (Leu) to 74% (Ala), compared with 70% for total N. The low value of leucine was ascribed to the constant marker infusion condition. In pigs infused with 13C-leucine, a similar endogenous proportion was obtained for lumenal leucine with 13C-leucine and 15N-leucine infusion. However, the 13C-enrichment of the leucine bound to mucin was markedly lower than that of plasma leucine (38%). The endogenous amino acid flows were also estimated by combining the ileal N flow measured with 15N and the endogenous amino acid profile obtained by means of an N-free diet. They were different from those obtained with the 15N-amino acid dilution technique. We conclude that the precursor pool currently used (plasma total N or total alpha-amino acid N pools) is a poor indicator of the enrichment of the secretions and that the infusion of one labeled amino acid is not sufficient to extend the method at the amino acid level. [ABSTRACT FROM AUTHOR]

Endogenous protein loss at the end of the small intestine was determined in two experiments using 10 pigs surgically prepared with end-to-end ileo-rectal anastomosis to allow total collection of ileal digesta. In the first experiment pigs were fed graded protein levels of 0 (protein-free), 55, 110 or 165 g/kg diet. Optimal durations for the adaptation and collection periods were found to be 4 and 3 d, respectively (combination 4:3), as shown by the higher correlation coefficient (r2 = 0.95) between excreted and ingested nitrogen compared with the other combinations tested (5:2, 5:3, 9:3, 9:5). The estimated amounts of endogenous N and amino acids were less accurate and tended to be smaller (P < 0.20) when obtained by extrapolation to zero nitrogen intake than when measured in pigs fed the protein-free diet. The endogenous protein was rich in proline, glutamic acid, glycine, aspartic acid, serine and threonine. In comparison to other amino acid patterns, this composition suggested a low bacterial contamination of the digesta. In the second experiment three levels of dietary fiber from wheat straw, corn cobs and wood cellulose were studied in pigs fed protein-free diets. Between 17 and 34 g crude fiber/kg diet, fiber increased the endogenous losses of nitrogen and amino acids per kilogram of dry matter intake (P < 0.05), but the excretion reached a plateau at higher dietary fiber concentration (102 g/kg). In contrast, glucosamine and galactosamine excretion increased continuously and linearly (P < 0.05) with fiber intake. We conclude that endogenous amino acid loss may be considered constant at usual and high levels of the fibrous mixture under study. [ABSTRACT FROM AUTHOR]

Investigates the efficiency of dietary tryptophan (Trp) for protein and Trp accretion in pigs. Growth performance and nitrogen retention; Amino acid composition of body protein and of body protein gain; Daily amino acid retention; Efficiency of protein and amino acid utilization.

Threonine oxidation to glycine was investigated in vivo in twelve growing pigs (27·4 kg live weight) fed on one of the following three diets with graded levels of threonine supply: a low-threonine diet (LT), a control well-balanced diet (C) or a high-threonine diet (HT), during 10h constant infusion of L-[1-13C]threonine and [2-3H]glycine in the cranial vena cava and [l-14C]glycine in the portal vein.13C-threonine and glycine enrichments and [3H]glycine and [14C]glycine specific radioactivities (SR) were determined at plateau in peripheral venous plasma, liver and pancreas. Glycine praduction rates calculated from plasma [2-3H]glycine or [1-14C]glycine SR gave similar values suggesting that [l-14C]glycine SR could be used in order to estimate whole-body glycine flux. The high pancreas [1-13C]glycine enrichment provided evidence that the pancreas may be, with the liver, a major site of threonine oxidation to glycine. Moreover, the present findings suggest that threonine transport into the Liver could be the limiting step of threonine oxidation in this tissue when dietary threonine supply is low. Total threonine oxidation to glycine, calculated from plasma values of enrichment and specific radioactivity, was low and constant when the estimated absorbed threonine was lower than 4 g/d and increased for higher amounts of absorbed threonine. [ABSTRACT FROM PUBLISHER]

We assessed the influence of sampling site when using the isotope dilution method to determine ileal endogenous N losses. Three growing pigs were prepared with ileorectal anastomoses and fitted with three catheters (portal, jugular and carotid). A 15N-leucine solution was infused for 24 d, alternating between the carotid artery and the jugular vein. Blood was sampled from the portal catheter and from the systemic catheter not used for the infusion. The pigs were fed successively a protein-free diet, an isolated pea protein diet and a hydrolyzed pea protein diet according to a Latin-square design. The 15N was transferred from leucine to isoleucine, valine, alanine, glycine and proline. Free 15N alanine, glycine and valine enrichments were closer to the respective amino acid enrichments in secretory tissues in the portal vein than in the systemic blood. The enrichment of total nitrogen was higher in the trichloroacetic acid-soluble fraction of the plasma than in the ileal digesta of pigs fed the protein-free diet. Lysine enrichment was significantly different from zero in all tissues except muscle, suggesting that essential amino acids can be synthesized by microflora and used for protein synthesis in the host. We conclude that the total nitrogen isotope dilution method is inappropriate to determine the endogenous loss of amino acids. Moreover, the amino acid dilution method should be performed with portal blood sampling. The main limitation of this method is that a number of essential amino acid losses cannot be determined. [ABSTRACT FROM AUTHOR]

Tryptophan (TRP) is an essential amino acid which content does not exceed 1.1% of whole-body protein. Apart from its incorporation into body proteins, TRP is known to play important biological roles, most of them being associated to metabolic pathways involved in its catabolism. Tryptophan deficiency was shown to depress the appetite parallel to slower gastric emptying and reduced insulin secretion in young pigs. However, independent of the latter effects, tolerance to glucose was reduced. This role of TRP in sensitivity to insulin appeared to depend on vitamin B6 supply. Otherwise, tryptophan transport and availability in the brain is one of the limiting steps for synthesis of serotonin which is involved in the appetite for protein. Serotonin is also involved in sleep, mood and stress response. It was recently shown that pigs receiving a large excess of TRP exhibit lower cortisol and catecholamine response to social stress. However, from a quantitative point of view, the proportion of tryptophan used for the production of serotonin is very low: less than 10% of tryptophan that is degraded would be into serotonin. Most of TRP degradation occurs through the kynurenine pathway. Two enzymes are involved in the first step of this pathway: TDO located in the liver degrades excess TRP; we focus our talk on the second enzyme, IDO expressed by immune cells and tissues targets by inflammation. Increased TRP catabolism through the IDO pathway occurs during inflammatory states and immune stress leading to reduced TRP availability when this amino acid is not provided at a sufficient amount by the diet. We showed that pigs fed with a low TRP diet were more sensitive to an inflammatory stress. We will discuss what can be the roles of TRP catabolism through IDO pathway in the regulation of T cells proliferation and the production of antioxidant molecules. [ABSTRACT FROM AUTHOR]

Two trials were performed to measure the apparent ileal digestibilities (AID) of amino acids (AA) in eight legumes (two faba beans and two lupins batches in experiment 1, four peas in experiment 2) and to estimate their standardised true ileal digestibility (SID). The effect of dehulling was investigated in one faba bean batch rich in tannins (experiment 1) and the effect of extrusion on one winter pea batch rich in trypsin inhibitor (experiment 2). In experiment 1, dietary dry matter AID was significantly lower with lupins than with faba beans. However, AA AID and SID were generally higher in the Australian lupin than in faba beans. Tryptophan AID (66.7) was lowest with the Alfred faba bean and increased by 20% after dehulling of the seeds up to the value obtained with the Australian lupin. Cystine (AID 55.5, SID 65.1) and tyrosine (AID 74.7, SID 78.1) were the other least digestible AA in the Alfred faba bean and digestibility did not improve significantly after dehulling. Lysine SID was lower (P<0.05) in the Lublanc lupin (81.4%) than in the dehulled Alfred and Blandine faba beans and in the Australian lupin, which were very close (88.1, 88.8 and 88.4, respectively.). In experiment 2, dietary dry matter AID was significantly higher (P<0.01) in the extruded Frile&grave;ne pea than in all other peas including the untreated Frile&grave;ne (77.6 versus 70.8). The same was true for protein (SID 89.1 versus SID 77.6) and the sum of AA (SID 91.6 versus SID 80.1). The most important relative improvements were noted for tryptophan (+31.3% for AID) and cystine (+38% for SID). Compared to European spring peas (Amino, Finale), quite low AID values were observed in the Australian and Frile&grave;ne peas for methionine (61.5, 64.2), threonine (62.6, 65.3), tryptophan (54.7, 57.6) and cystine (56.1, 53.4), while lysine AID were higher (79.6, 77.6). After correction for basal endogenous losses, the sulphur amino acids, methionine (SID 68.7, 70.4) and cystine (SID 66.0, 62.8) remained the least digestible amino acids in the Australian and Frile&grave;ne pea. These data allow relating nutritional value to species and variety, in terms of their ANF contents, and demonstrate the efficiency of technological treatments. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]