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Feed-use (FU) amino acids, at constant performance, make it possible to reduce the protein content of pig feeds and nitrogen excretion by the animals. The aim of this study was to assess the environmental impact of pig production in a conventional farm by Life Cycle Assessment (LCA) according to several scenarios of FU amino acid incorporation. Two modalities of waste management (slurry or solid manure), two hypotheses of protein sources (soybean meal only, or soybean meal, rapeseed meal and pea) and two soybean origins (Centre-West Brazil vs. average Brazilian soybean) were considered. In each scenario investigated, gestating, lactating, pre-starter and starter feeds were formulated. Fattening pigs were fed either with only one feed (1P), or with two feeds (2P) or according to multiphase feeding (MP). In three scenarios, feeds were least-cost formulated: without incorporation of FU amino acids (NoAA), with FU amino acid incorporation and reduced protein content (LowCP), and FU amino acid incorporation with free protein content (Min€). In the fourth scenario (MinCP), feeds were formulated to minimize protein content. The average protein content of pig feeds decreased, from 190 g/kg in 1P-NoAA down to 123 g/kg in MP-MinCP while FU amino acid incorporation increased. At the same time, the incorporation of soybean meal into feeds decreased from 197 kg/t down to 70 kg/t in MP-MinCP. This reduction of soybean meal incorporation was concomitant with a decrease in feed cost. The incorporation of FU amino acids in low protein diets clearly reduced the impacts of pig production on Climate Change (CC), Acidification (AC) and Eutrophication (EU). The lowest CC, AC and EU potential impacts were reached with the Min€ or MinCP scenarios, for which tryptophan and valine were incorporated in pig feeds. The impacts on terrestrial ecotoxicity, cumulative energy demand and land occupation were less sensitive to the studied scenarios. The combination of FU amino acid incorporation and multiphase feeding of growing-finishing pigs produced the largest reduction of CC, AC and EU impacts. The underlying mechanisms include the substitution of soybean meal and extruded soybean by cereals and FU amino acids and the reduction of nitrogen excretion which further reduces nitrous oxide and ammonia emissions. This study suggests that environmental impacts of pig production in France can be further reduced through feeding practices, especially for acidification, eutrophication and climate change.

Effect of total substitution of soybean meal in a low-protein diet fed to finishing broilers. 22nd European Symposium on Poultry Nutrition

Effet de la substitution totale du soja dans un aliment à bas taux protéique chez le poulet de chair en finition. 13èmes Journées de la Recherche Avicole et Palmipèdes à Foie Gras

In order to control and optimize chicken quality products, it is necessary to improve the description of the responses to dietary amino acid (AA) concentration in terms of carcass composition and meat quality, especially during the finishing period. The aim of this study was to investigate the effects of Lysine (Lys, i.e. a limiting AA used as reference in AA nutrition) and AA other than Lys (AA effect). In total, 12 experimental diets were formulated with four levels of digestible Lys content (7, 8.5, 10 and 11.5 g/kg) combined with either a low (AA-), adequate control (AAc) and high (AA+) amount of other essential AA (EAA) expressed as a proportion of Lys. They were distributed to male Ross PM3 from 3 to 5 weeks of age. No significant AA×Lys interaction was found for growth performance or carcass composition. Body weight and feed conversion ratio were significantly improved by addition of Lys but were impaired in broilers receiving the AA- diets, whereas breast meat yield and abdominal fat were only affected by Lys. No additional benefit was found when the relative amount of other EAA was increased. There was a significant AA×Lys interaction on most of the meat quality traits, including ultimate pH, color and drip loss, with a significant effect of both AA and Lys. For example, AA- combined with reduced Lys level favored the production of meat with high ultimate pH (gt;6.0), dark color and low drip loss whereas more acid, light and exudative meat (lt;5.85) was produced with AA+ combined with a low Lys level. In conclusion, growth performance, carcass composition and meat quality are affected by the levels of dietary Lys and AA in finishing broilers. In addition, interactive responses to Lys and AA are found on meat quality traits, leading to great variations in breast pHu, color and drip loss according AA balance or imbalance.

On commercial farms, young growing pigs are frequently affected by health problems from multifactorial origins (e.g. environmental changes, biosecurity, management, and feed) that result in inflammation and activation of body defenses. Inflammation states alter animal metabolism in such a way that nutrients (particularly amino acids) are diverted from the use for growth towards the production of defense-related proteins and low-molecular-weight compounds (e.g., nitric oxide, H2S, and glutathione) for supporting the activity of rapidly dividing cells such as immune cells and enterocytes. Furthermore, amino acids may act specifically as signaling molecules to regulate metabolic pathways during inflammation. Thus, new knowledge on the specific role and metabolism of each amino acid is needed to refine nutritional recommendations for pigs of different phenotypes and genotypes, with the objective of maintaining animal health and performance under sub-optimal rearing conditions. This paper aims at summarizing recent advances in research on the functional roles of amino acids related to swine health. Specifically, the review highlights current knowledge on the impact of inflammation on the intake and metabolism of amino acids; their relevance for the physical gut mucosal barrier and antioxidant defense, as well as their roles in the syntheses of defense molecules and in the regulation of immune response. Practical implications for feeding strategies adapted to various health conditions of growing pigs are also discussed along with our general perspectives on related research.

The objective was to define the Val requirement for weaned piglets in the context of reducing the dietary protein content. A dose–response experiment was conducted to estimate the standardized ileal digestible (SID) Val to Lys ratio required to support the optimum growth of post-weaned piglets. In this study, 96 pigs weighing 8 kg were allotted to one of six dietary treatments (16 pigs for each dietary treatment) and were housed individually. Diets were formulated to provide 0.58, 0.62, 0.66, 0.70, 0.74 and 0.78 SID Val : Lys by adding graded levels of crystalline L-Val to the 0.58 SID Val : Lys diet. Lysine was sub-limiting and supplied 90% of the recommendation (10.95 g SID Lys/kg equal to 11.8 g/kg total Lys). Average daily feed intake (ADFI), average daily gain (ADG) and gain to feed ratio (G : F) were determined during a 14-day period of ad libitum feeding. Blood and urine samples were taken at the end of each week (day 7 and 14 of the experiment) 3 h after feeding the experimental diets. The maximum ADFI and ADG were obtained in pigs fed the 0.78 SID Val : Lys diet; it was not different from the results of pigs fed 0.70 SID Val : Lys diet. The highest G : F was obtained in pigs fed 0.70 SID Val : Lys. The plasma concentration of Val increased linearly ( P

Use of feed-grade amino acids in low protein diets: Towards a more sustainable broiler production?. 68th EAAP Annual Meeting

Traditional AA dose-response studies utilize many animals for evaluation of growth performance, and it is hypothesized that a new experimental design based on modem analytical techniques can reduce the number of used animals. The objective was to evaluate a short-term approach with a low number of pigs based on plasma metabolites as a method to determine the dietary Ile, Leu, and Val requirements. Three separate 6 x 6 Latin square experiments having 6 replicates per treatment were conducted with 6 diets containing increasing concentrations of Ile, Leu, and Val which were fed to 6 pigs (BW 8-9 kg) for 2 days, each without a wash-out period for a period of 12 days. The diets were prepared and used in 3 previous traditional-design dose-response studies and had been stored at 20 degrees C. Blood samples were collected at the end of each 2-day period, and plasma was analyzed for AA and other metabolites using a metabolomics approach. Out of the 18 analyzed plasma AA, 11, 16, and 3 AA for Ile, Leu, or Val, respectively, showed linear or quadratic responses (P < 0.05) which could be linked to animal growth. The same was found for 4 non-AA metabolites in the Ile, and for 7 non-AA metabolites in the Leu study. 3-Methyl-2-oxovaleric acid, ketohexanoic acid, and a-ketoisovaleric acid were discriminating metabolites for both Ile and Leu. It was possible to fit least squares means of 5, 14, and 2 metabolites in the Ile, Leu, and Val experiments to curvilinear-plateau, broken-line, or quadratic models and thereby estimate an optimum dietary BCAA level. The average optimum BCAA levels across metabolites and models were 0.54 standardized ileal digestible (SID) Ile:Lys, 1.04 SID Leu:Lys, and 0.68 SID Val:Lys which were close to optimums of 0.52, 0.93, and 0.70 found in the previous dose response studies based on animal growth performance. In conclusion, certain plasma metabolites could be used to estimate Ile, Leu, and Val requirements, and 2 days of adaptation to a new diet was sufficient to reflect relevant biological changes in the blood to different levels of dietary AA in the current study.

Réduction du taux protéique dans l’aliment finition chez le poulet de chair: Conséquences environnementales. 12.Journées de la recherche avicole et palmipèdes à foie gras

Réduction du taux protéique dans l’aliment finition chez le poulet de chair: Effets sur les performances zootechniques, les rendements et la qualité de la viande. 12.Journées de la recherche avicole et palmipèdes à foie gras

Environmental implications of reducing dietary crude protein in broilers. XXXI Jornadas Téchnicas de Indukern

Lysenkoism as a practice, theory and ideology was introduced in Romania in 1949, as part of the structural changes of the scientific institutions, namely the subordination of the Romanian Academy to the communist state. Beyond the similarity with other countries of the Eastern bloc, the original trend in the case of Romania was the interference between Lysenkoism and the neo-Lamarckian context, strongly represented before World War II in biology and agronomy. This explains the fact that Romanian scientists maintained references to Michurin until the early 1970s, long after the official introduction of genetics. The national pattern of Lysenkoism focused on the continuity of the Romanian science.

Besides being incorporated into proteins, Trp, an indispensable AA, is involved in numerous metabolic pathways. Previous data showed that Trp conversion into kynurenine (Kyn) and nicotinamide (Nam) differs among studies, and such differences cannot be explained by different dietary niacin supplies. We hypothesized that pig genotype influences Trp metabolism and thus the conversion of Trp into its metabolites. The objective of this study was to compare plasma appearance of Trp and related metabolites in 12 Duroc and 12 Piétrain crossbred postweaning pigs fed 2 contrasting dietary Trp levels. Within each genotype, 6 pigs were fed a basal (B-Trp: 17% and 15% standardized ileal digestible [SID] Trp:Lys for starter and prestarter diets) or supplemented (S-Trp: 24% and 23% SID Trp:Lys for starter and prestarter diets) Trp diet. Growth was monitored, and plasma fasted concentrations were measured over 4 wk, and then pigs were fitted with a jugular catheter for frequent blood samplings. After overnight fasting, 350 g of the experimental diets were offered to each pig, and plasma concentrations of Trp, Kyn, Nam, and 5-hydroxytryptamine (5-HT) were measured for 6 h. The activities of Trp-degrading enzymes were measured in different tissues collected after pig slaughtering. Plasma Trp fasted concentrations did not differ between B-Trp and S-Trp diets and increased from weaning to 2 and 4 wk after weaning for Piétrain but not for Duroc crossbred pigs (time × genotype, = 0.001). Plasma Kyn concentrations were greater 4 wk after weaning ( = 0.002) than at weaning and for Piétrain compared to Duroc genetics ( = 0.008). Plasma Nam concentrations were greater for pigs fed the S-Trp diet than for those fed the B-Trp diet ( = 0.0001) and for Duroc than for Piétrain genetic lines ( = 0.001); this difference tends to be greater at weaning than after ( = 0.055). Our data showed an increase in plasma concentrations of Trp, Kyn, Nam, and 5-HT according to time after a meal and to the dietary Trp content. However, postprandial plasma concentrations of Trp metabolites and enzyme activities were not significantly different between Duroc and Piétrain crossbred pigs. In conclusion, our results suggest that Nam endogenous synthesis capacity from Trp is greater in Duroc than in Piétrain crossbred pigs, but this was apparent only at weaning.

Eighteen multiparous Large White sows were used to determine the effects of dietary protein content and lactation stage on milk composition during a 28-d lactation under humid tropical climatic conditions. This study was conducted at the INRA facilities in Guadeloupe, French West Indies (latitude 16°N, longitude 61°W). The average minimum and maximum ambient temperatures and average daily relative humidity during the trial were 22.7 and 29.4°C, and 93.7%, respectively. The dietary experimental treatments were a normal protein (NP, 17.3%) diet and a low protein (LP, 14.1%) diet supplemented with essential amino acids. The ADFI tended to be higher for the sows fed the LP diets when compared with the NP treatment (i.e., +9%, P0.10). The treatments did not influence (P>0.10) sow body weight loss during lactation. The sows fed LP diets tended to show lower backfat thickness losses when compared to the sows fed NP diets (2.4 vs. 6.3 mm, respectively; P0.10). Milk dry matter and ash contents linearly increased according to lactation stage (17.6 to 19.9%, and 0.72 vs. 97%, respectively from d 7 to d 27; P0.10) by lactation stage. Maternal BW loss during lactation was negatively correlated with the average daily feed intake (r=-0.76; P

Reducing the CP level of the diet allows for a reduction in N excretion without limiting performance as long as the amino acid (AA) requirements are covered. The availability of crystalline AA has permitted for a considerable reduction in the CP level of diets, practically used in pig nutrition. The adoption of low CP diets and the extent to which the CP content can be reduced further depends on the knowledge of the minimum levels of indispensable AA that maximize growth. The standardized ileal digestible (SID) Phe : Lys and Tyr : Lys requirements and the possibility to substitute Tyr by Phe have never been studied in piglets. The objectives of this study were to estimate these requirements in 10 to 20 kg pig as well as to determine the extent to which Phe can be used to cover the Tyr requirement. In three dose–response studies, six pigs within each of 14 blocks were assigned to six low CP diets (14.5% CP) sub-limiting in Lys at 1.00% SID. In experiment 1, the SID Phe : Lys requirement estimate was assessed by supplementing a Phe-deficient diet with different levels of L-Phe to attain 33%, 39%, 46%, 52%, 58%, and 65% SID Phe : Lys. Because Phe can be used for Tyr synthesis, the diets provided a sufficient Tyr supply. A similar approach was used in experiment 2 with six levels of L-Tyr supplementation to attain 21%, 27%, 33%, 39%, 45% and 52% SID Tyr : Lys. Phenylalanine was supplied at a level sufficient to sustain maximum growth (estimated in experiment 1). The SID Phe : Lys and SID Tyr : Lys requirements for maximizing daily gain were 54% and 40% using a curvilinear-plateau model, respectively. A 10% deficiency in Phe and Tyr reduced daily gain by 3.0% and 0.7%, respectively. In experiment 3, the effect of the equimolar substitution of dietary SID Tyr by Phe to obtain 50%, 57%, and 64% SID Phe : (Phe +Tyr) was studied at two limiting levels of Phe +Tyr. From 57% to 64% SID Phe : (Phe +Tyr), performance was slightly reduced. In conclusion, it is recommended not to use a Phe +Tyr requirement in the ideal AA profile but rather use a SID Phe : Lys of 54% and a SID Tyr : Lys of 40% to support maximal growth.

Accroitre l’efficacité des stratégies alimentaires tout en réduisant l’apport protéique des aliments est un enjeu majeur pour la durabilité de la filière avicole, que ce soit d’un point de vue économique, environnemental et social. Les aliments sont classiquement formulés avec un niveau de protéines (MAT) conséquent avec une incorporation massive de tourteau de soja, matière première problématique quant à la volatilité de son prix, son coût environnemental (transport, déforestation) et sa culture majoritairement OGM. La réduction du niveau d’apport protéique combinée à l’ajout d’acides aminés (AA) libres permet de réduire l’utilisation de soja mais aussi l’excrétion azotée. Cependant, contrairement à ce que l’on observe chez le porc, le maintien des performances de croissance et de rendement n’est pas systématique chez le poulet lorsque l’on réduit la MAT du régime. L’objectif de ce travail a donc été d’étudier les freins à la baisse de protéines des régimes de poulets afin de proposer des solutions nutritionnelles qui permettent le maintien des performances sans compromettre de la qualité des produits en période de croissance-finition. Une baisse de l’apport protéique ne peut s’envisager que si les besoins en AA indispensables (AAI) des poulets sont satisfaits avec des apports équilibrés (protéine idéale respectant un profil où les AAI sont exprimés en proportion de la lysine). Les données bibliographiques que nous avons compilées dans le cadre d’une méta-analyse montrent de grandes distorsions de résultats que la diversité des protocoles utilisés lors d’essais baisse de protéines pourraient expliquer. Elles montrent en particulier que la quantité d’AA sous forme libre ajoutée dans les régimes ainsi que les profils utilisés sont deux facteurs très variables. La première partie de cette thèse a alors été consacrée à l’étude de l’impact du profil en acides aminés sur la réponse des animaux et de sa possible interaction avec le niveau de Lysine digestible apportée dans la ration. Dans un second temps, nous avons analysé l’effet de la forme d’apport protéique de la ration. Les mécanismes d’une éventuelle adaptation de la physiologie digestive ont également été explorés. Ces facteurs n’étant pas limitants dans les conditions classiques de formulation, nous avons étudié la réponse du poulet à des apports réduits en protéines. Nous avons examiné, au cours de deux essais, les performances des animaux nourris avec un aliment témoin à teneur classique en protéines (19% de MAT) comparés à ceux nourris avec des aliments dont la teneur en protéines est réduite jusqu’à 15% ou 16% de MAT en équilibrant les apports en AAI. Nous montrons qu’une baisse jusqu’à 17% de MAT, dans la mesure où l’apport en AAI est bien contrôlé et respecte le concept de la protéine idéale, n’altère pas les performances et les rendements en muscles, module la qualité de la viande tout en réduisant l’excrétion azotée. Pour envisager une baisse inférieure à 17% de MAT, un troisième essai a été mis en place afin d’explorer la possibilité que certains AA non indispensables (AANI) soient limitants. Les résultats présentés ne montrent aucune évidence permettant de considérer ces AANI comme des facteurs limitants à la baisse de protéines dans nos conditions expérimentales. Dans l’avenir, il sera nécessaire de combiner les approches (méta-analyses, études nutritionnelles et métaboliques), d’intégrer les données obtenues à différents niveaux d'échelle (de la cellule à l'animal voire au système d’élevage) et la compréhension du métabolisme des AA, pour fournir les bases de recommandations nutritionnelles pertinentes incluant une nutrition des poulets de plus en plus précise

International audience; The objective of the current study was to identify biomarkers of branched chain amino acids (BCAA) intake status that could be linked to the best animal growth perfonnance. Three dose-response studics were carried out to collect blood and urine samples from pigs fed diets with increasing levels of isoleucine (Ile), valine (Val), or leucine (Leu) followed by a non-targeted LC-MS approach to characterize the metabolic profile of plasma and urine, when the level of BCAA in the diet is optimum for the best animal growth performance. The LC-MS method could separate and identify the plasma and urine metabolites which were discriminating the pigs fed optimum dietary level of Ile, Val, and Leu. Among the discriminating plasma and urine metabolites, that correlated closely to the highest animal growth performance, were plasma glycocholic acid and taurocholic acid as biomarkers of the optimum Ile level in the diet, and plasma creatine and urinary 2-aminoadipic acid, ascorbic acid, and choline as biomarkers of optimum Leu level. No good biomarkers were identified in the Val study.

National audience; The effects of tryptophan (Trp) supplementation were investigated in growing pigs (n = 100 from 40 to 100 kg) fed ad libitum in a context of a reduction of the crude protein (CP) level. A control diet with a CP content close to the standard level (NP; 16.5%) was compared to four low CP diets (LP; 13.7%) gradually supplemented with L-Trp (0, 0.3, 0.6 and 0.9 g/kg for LP0, LP1, LP2 and LP3, respectively). All the diets were formulated to contain similar net energy (9.9 MJ/kg) and standardized ileal digestible (SID) lysine (Lys; 0.81%) contents. The actual SID Trp:Lys ratios were 22, 17, 20, 23 and 27% for NP, LP0, LP1, LP2, and LP3 diets, respectively. Growth performance decreased when pigs were fed a low CP diet without L-Trp supplementation (LP0 vs. NP, -160 g/d; P < 0.05). The average daily gain of pigs fed the LP1 diets was similar to that obtained with NP treatment (958 vs. 989 g/d; P > 0.05). Similar growth performances were measured in LP1, LP2 and LP3 groups. In our experimental conditions, the SID Trp:Lys ratio in growing pigs fed a low CP diet has to be at least 20% to optimize the growth performance.

National audience; The effects of tryptophan (Trp) supplementation were investigated in growing pigs (n = 100 from 40 to 100 kg) fed ad libitum in a context of a reduction of the crude protein (CP) level. A control diet with a CP content close to the standard level (NP; 16.5%) was compared to four low CP diets (LP; 13.7%) gradually supplemented with L-Trp (0, 0.3, 0.6 and 0.9 g/kg for LP0, LP1, LP2 and LP3, respectively). All the diets were formulated to contain similar net energy (9.9 MJ/kg) and standardized ileal digestible (SID) lysine (Lys; 0.81%) contents. The actual SID Trp:Lys ratios were 22, 17, 20, 23 and 27% for NP, LP0, LP1, LP2, and LP3 diets, respectively. Growth performance decreased when pigs were fed a low CP diet without L-Trp supplementation (LP0 vs. NP, -160 g/d; P < 0.05). The average daily gain of pigs fed the LP1 diets was similar to that obtained with NP treatment (958 vs. 989 g/d; P > 0.05). Similar growth performances were measured in LP1, LP2 and LP3 groups. In our experimental conditions, the SID Trp:Lys ratio in growing pigs fed a low CP diet has to be at least 20% to optimize the growth performance.

Several aspects of tryptophan (Trp) metabolism are dependent upon pyridoxine (B 6 ) status. The present experiment aimed to determine if Trp metabolism and the eventual growth responses to dietary supplementation of Trp is modulated by dietary B 6 . Exploratory measurements related to the modulation of the immune system were also made. Piglets weaned at 15 to 18 days of age ( n = 544) were grouped in 32 pens of 17 animals and distributed in a factorial arrangement of treatments with two dietary additions of B 6 [0 (B 6 −) or 5 mg/kg (B 6 +)] and two dietary additions of synthetic Trp [0 (Trp−) or 0.5 g/kg (Trp+)]. Basal dietary concentrations of B 6 varied according to age, between 2.1 and 3.5 mg/kg, and for Trp, between 1.9 and 2.5 g/kg. Growth performance was recorded every week from 2 to 9 weeks of age. Blood samples were taken from two piglets in each pen at 2, 4, 6 and 8 weeks of age. Another piglet in each pen was immunized twice with ovalbumin emulsified with incomplete Freund adjuvant to evaluate the antibody response. No treatment effect was observed on feed intake, body weight gain or feed conversion ratio for the whole experimental period but feed conversion increased more drastically in Trp− than in Trp+ piglets during the last week of experiment (B 6 × Trp × age, P 6 vitamer, was 19% lower in red blood cells of B 6 − than B 6 + piglets (B 6 × age, P 6 + than in B 6 − piglets. The percentage of B lymphocyte population at 4 and 6 weeks of age dropped in B 6 − animals whereas it remained stable in B 6 + piglets (B 6 × age, P 6 × Trp × age), the results indicate that, globally, within the present dietary levels, pyridoxine is not a major factor for Trp metabolism and therefore, for Trp requirements of post-weaning piglets. The absence of interaction between B 6 and Trp on the present immunological indicators suggest that each nutrient modulates the immune response through independent mechanisms.

International audience; The branched-chain amino acids (BCAA) valine (Val) and isoleucine (Ile) are considered to be among the next-limiting amino acids for growth in piglets. In earlier studies, we estimated the standardized ileal digestible (SID) Val : Lys (lysine) requirement to be at least 70%, whereas the Ile : Lys requirement may be as low as 50%. Because the BCAA partially share a common route of catabolism, the supply of one BCAA may affect the availability of the other BCAA. Four experiments were conducted to determine the response of 6-week-old piglets to the Val supply in relation to the other BCAA. A deficient supply of Val or Ile typically results in a reduction in average daily feed intake (ADFI). Experiment 1 was designed to determine the effect of a limiting Val supply, independent of the effect on feed intake. In a dose–response study using restrictively fed piglets, nitrogen retention did not increase for an SID Val : Lys supply greater than 64%. In the remaining experiments, piglets were offered feed ad libitum using ADFI, average daily gain (ADG) and gain-to-feed ratio as response criteria. The interaction between the Val and leucine (Leu) was studied in Experiment 2 in a 2 × 2 factorial design (60% and 70% SID Val : Lys, and 111% and 165% SID Leu : Lys). Performance was considerably lower in piglets receiving 60% Val : Lys compared with those receiving 70% Val : Lys and was lowest in piglets receiving the diet with low Val and high Leu content. To further evaluate the interaction between Val and Leu, a dose–response study was carried out in which the response to Val supply was studied in combination with high Leu supply (165% Leu : Lys). Using a curvilinear-plateau model, the average SID Val : Lys requirement was 72%. However, low Val supply (60% SID Val : Lys) reduced performance by 13% to 38%, which was much greater than what we observed in earlier studies. Experiment 4 was carried out to test the hypothesis that the Val requirement is not affected by low Ile supply (50% SID Ile : Lys). Performance was not improved for Val : Lys supplies greater than 65%, which may indicate that Ile (and not Lys) was second-limiting in this study. In conclusion, the first response of piglets to deficient Val supply appears to be a reduction in ADFI, rather than a reduction in ADG or nitrogen retention. A large supply of Leu may not affect the Val requirement per se, but may aggravate the consequences of Val deficiency.

International audience; 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.

Etat des lieux et nouvelles perspectives de la nutrition protéique en poulet de chair. Réunion technique Altilis-Ajinomoto

Threonine requirement of broiler chickens: integrated prediction by meta-analysis. 20th European Symposium on Poultry Nutrition

International audience

Organised by The Working Group 2: Nutrition of the European Federation of Branches of the World’s Poultry Science Association (WPSA) and The Czech Branch of the WPSA; Is meta-analysis an effective tool to estimate the glycine plus serine requirement of broiler chickens? . 20. European Symposium on Poultry Nutrition (ESPN)

International audience

Revisiting amino acid nutrition. 20th European Symposium on Poultry Nutrition (ESPN)

De récentes études ont estimé les besoins en valine, isoleucine et leucine chez le porcelet. Bien que l’on puisse faire l’hypothèse que ces besoins peuvent être extrapolés aux porcs en phases de croissance et finition, cela n’a pas été confirmé expérimentalement. L’objectif est d’évaluer la réponse des porcs en croissance et finition à l’apport en valine, lysine et matières azotés totales (MAT) du régime. Des porcs alimentés à partir de 45 ou 90 kg de poids vif pendant 3 semaines avec trois régimes à teneurs différentes en valine, lysine et MAT. Un régime à bas taux protéique (régime A) a été formulé pour être limitant en valine [58% digestibilité iléal standardisé (DIS) valine:lysine] et sub‐limitant en lysine. Deux régimes ont couvert les besoins en valine (régime B) et en valine et lysine (régime C). Le régime D était similaire au régime C mais avec un haut niveau en MAT. Aux deux stades, la consommation et la croissance ont été réduites de 10‐15% chez les animaux qui recevaient le régime A en comparaison avec les autres. La meilleure performance a été observée chez les animaux qui recevaient les régimes B et C, sans différence entre eux. La consommation était ou tendait à être réduite chez les animaux recevant le régime D en comparaison avec les régimes B et C. En conclusion, la réduction de la MAT dans l’aliment n’a pas eu d’impact sur les performances des porcs en croissance et finition quand les besoins en acides aminés étaient couverts. Il apparaît également que la valine est potentiellement limitante dans l’alimentation de ces porcs., Recent studies have been carried out to determine the requirements for valine, isoleucine, and leucine in piglets. Although it is hypothesized that these requirements can be extrapolated to growing and finishing pigs, this has not been confirmed experimentally. The objective of this study was to test the response of growing and finishing pigs to the valine, lysine, and crude protein (CP) contents in the diet. Pigs with an initial body weight of 45 or 90 kg were fed for 3 weeks with diets differing in valine, lysine and CP contents. A low‐CP diet (diet A) was formulated to be limiting in valine [58% standardized ileal digestible (SID) valine:lysine] and sub‐limiting in lysine. Two other diets (based on diet A) were formulated to cover the valine requirement (diet B) and valine and lysine requirements (diet C). Diet D was similar to diet C but with a higher CP content. At both stages, feed intake and growth rate were 10‐15% lower in pigs receiving diet A compared to those receiving the other diets. The best performance was observed in pigs receiving diets B and C, with no difference between these treatments. Feed intake was or tended to be lower in pigs receiving diet D compared with those receiving diets B and C. In conclusion, a reduction in the dietary CP content had no impact on performance of growing and finishing pigs as long as the amino acid requirements were met, and valine can be a potentially limiting amino acid in the diet of these pigs.

This study aimed at refining the response of piglets to different supplies of standardized ileal digestible (SID) isoleucine (Ile), valine (Val), and leucine (Leu). Three 2‐week experiments were carried out with piglets, initially weighing 7 kg and which were penned individually. One week after weaning, piglets (16 per treatment) were offered ad libitum the experimental diets. These diets were sub‐limiting in lysine (Lys) and supplied 6 equidistant levels of either Ile (42 to 62% SID Ile:Lys), Val (58 to 78% SID Val:Lys), or Leu (70 to 120% SID Leu:Lys). Feed intake, body weight gain, and feed efficiency were determined each week. Significant performance responses were observed in the three dose‐response studies. Increased Ile levels had an effect on feed intake and weight gain, while increased levels of Val and Leu affected all performance traits. The estimated requirement values (levels obtained by the curvilinear‐plateau model to reach the plateau) were 52% SID Ile:Lys, 70% SID Val:Lys, and 100% SID Leu:Lys, and similar to literature data. An amino acid supply 10% below the requirement values determined for average daily gain (ADG) resulted in the reduction by 3% for Ile, 6% for Val, and 5% for Leu of the ADG.

La connaissance des besoins en protéines et en acides aminés des volailles reste un enjeu majeur car elle conditionne à la fois les performances, la qualité des produits, le coût de revient et les rejets environnementaux. Afin de déterminer l’impact d’un apport variable en protéines sur la réponse du poulet de chair, une base de données bibliographique a été établie. Une première base a été construite et regroupe 56 essais issus de 29 publications traitant la baisse de la teneur en protéine et publiées après 1990 pour s’affranchir du facteur de progrès génétique. Les informations recensées concernent à la fois les caractéristiques des protocoles, les performances et les caractéristiques nutritionnelles des régimes qui ont tous été recalculés sur une base commune (Table INRA-AFZ, Sauvant et al, 2004). Ceci permet d’obtenir les profils complets en acides aminés (AA) totaux et digestibles. De cette base 15 essais ont été sélectionnés selon 1) leur niveau de lysine digestible (dLys) qui devait être sub-limitant et constant au cours de la baisse de protéine et 2) leur profil en AA essentiels qui devait être équilibré selon la protéine idéale. Si la majorité des essais ne testent que 2 niveaux et ne permet pas d’aboutir à une loi de réponse, on remarque toutefois une variabilité des performances en réponse à la baisse de protéine, notamment au-delà d’un ratio dLys/MAT >6,5. La sélection ayant été faite sur le profil en AA « essentiels » (AAE), on remarque que certains AA « non essentiels » (AANE) varient dans notre base. Les interactions AAE/AANE peuvent être une piste d’explication de la variabilité des performances observées. Cette méta-analyse permet d’ores et déjà de présenter des singularités propres aux essais pour lesquels il y a maintien des performances et d’apporter des pistes de travail quant aux impacts de la baisse de protéine en poulet de chair., Knowledge of protein and amino acid (AA) requirements in poultry remains a major issue because it affects performance, product quality, diet price and environment impact. A bibliographic database was established to determine the effect of varying protein intake on the response of broilers. A first database included 56 trials originated from 29 publications focused on the decrease in dietary protein and selected after 1990 to overcome ‘genetic progress’. The information identified concerned the experimental design, chicken performance and the characteristics of diets which were recalculated on a common basis (Tables INRA-AFZ, Sauvant et al, 2004). The database therefore included the profiles of total AA and digestible AA. Fifteen trials were selected according to 2 ‘selection criteria’: 1) the level of digestible lysine (dLys) that had to be sub-limiting and constant when dietary protein was decreased, and 2) their profile in essential AA (EAA) that had to be consistent with ideal protein. After selection, results of trials were compiled and graphically analyzed to assess the effect of protein decrease on performance (consumption, weight gain and feed conversion ratio). The majority of the trials tested only two levels that did not lead to a law of response, but we noticed a low-protein related variability of performances above 6.5 of dLys/crude protein ratio. The selection was made according to the EAA profile but but some non-essential AA (NEAA) varied in our database. Interaction between EAA and NEAA had to be considered as a possible explanation of the performance variability observed. Without modeling the response of chicken performance to dietary protein decrease, this meta-analysis already allows to identify the specific peculiarities of trials in which performance are maintained and brings out some assumptions concerning the impact of low protein diets in broiler chickens.

The objective of the study was to estimate Leu requirement for weaned piglets to balance indispensable AA in reduced CP diets. A dose-response experiment was conducted to estimate the standardized ileal digestible (SID) Leu to Lys ratio required for the maximum growth of young pigs after weaning. In this study, 96 female pigs (initial BW of 8 kg) were allotted to 1 of 6 dietary treatments with 16 individually penned pigs per treatment. Graded levels of crystalline l-Leu were added to a basal diet to provide diets containing 0.70, 0.80, 0.90, 1.00, 1.10, and 1.20 SID Leu:Lys. Lysine was limiting and fulfilled 90% of the current recommendations. The ADFI, ADG, and G:F were determined during a 2 wk experimental period. Blood and urine samples were taken at the end of each wk. The ADFI increased linearly (P < 0.001) from 0.70 to 0.80 SID Leu:Lys and then remained constant from 0.90 to 1.20 SID Leu:Lys. The ADG showed a quadratic increase (P = 0.02), as the SID Leu:Lys level increased from 0.70 to 0.90 SID Leu:Lys and did not change further from 0.90 to 1.20 SID Leu:Lys. The G:F increased quadratically (P < 0.001) with increasing SID Leu:Lys level, and the greatest G:F was achieved with pigs receiving the diet with 0.80 SID Leu:Lys. Increasing the dietary SID Leu:Lys resulted in a linear increase in plasma Leu concentration (P < 0.001) and quadratic increases (P < 0.001) in plasma Cys concentration. The plasma concentration of most of the other AA was lowest in pigs receiving the diets with 0.90 to 1.00 SID Leu:Lys. The plasma urea nitrogen concentration tended (P = 0.08) to be lowest in pigs receiving 1.00 SID Leu:Lys, suggesting a more balanced AA profile at this level. Using a curvilinear-plateau model, the SID Leu:Lys requirement was estimated at 0.93 to maximize growth in female pigs weighing 8 to 12 kg.

Research on AA requirements and their profile is still running and the recommendations are being updated frequently. The dietary crude protein level could be reduced with no marked detrimental effects on animal performance as far as the supply and the balance of indispensable AA meet the animal requirements. A dose-response experiment was conducted to estimate the standardized ileal digestible (SID) isoleucine (Ile) to lysine (Lys) ratio required for the best performance of animals when fed cereal-based diets without blood products. In this study, 96 pigs (initial BW 8 kg) were allotted to 1 of 6 dietary treatments with 16 pigs per treatment. Graded levels of crystalline Ile were added to the basal diet to produce diets providing 0.42, 0.46, 0.50, 0.58, and 0.62 SID Ile:Lys. Average daily feed intake (ADFI), average daily gain (ADG), and feed conversion ratio (FCR) were determined during a period of 14 days. Blood and urine samples were taken at the end of each week. There was a quadratic increase in ADFI (P

The adoption of low-CP diets for pigs depends on the knowledge of the minimum levels of indispensableamino acids that maximize growth. Phe and Tyr are indispensable amino acids, although Tyr can be providedby biosynthesis from Phe. Both amino acids are constituents of body protein while Tyr is also a precursorfor catecholamines, neurotransmitters and thyroid hormones. Knowledge about the requirements for Pheand Tyr is very limited. The objectives of this study were to estimate these requirements in 10-20 kg pigand to determine the extent to which Phe can be used to cover the Tyr requirement. In three dose-responsestudies, pigs were assigned to diets with 14.5% CP with a sub-limiting level of standardized ileal digestible(SID) Lys of 1.00%. In experiment 1, the SID Phe:Lys requirement estimate was assessed by supplementinga Phe-deicient diet with different levels of L-Phe to attain 33, 39, 46, 52, 58, and 65% SID Phe:Lys, usingdiets with a suficient Tyr supply. A similar approach was used in experiment 2 with six levels of L-Tyrsupplementation to attain 21, 27, 33, 39, 45 and 52% SID Tyr:Lys, while Phe was supplied at a level suficientto sustain maximum growth (estimated in experiment 1). The SID Phe:Lys and Tyr:Lys requirements formaximizing daily gain were 54 and 40% using a curvilinear-plateau model, while a 10% deiciency reduceddaily gain by 3.0 and 0.7% for Phe and Tyr, respectively. In experiment 3, the effect of an equimolarsubstitution of dietary SID Tyr by Phe to obtain 50, 57, and 64% SID Phe:(Phe+Tyr) was assessed. From57 to 64% SID Phe:(Phe+Tyr), performance was slightly reduced indicating that Phe cannot be used on anequimolar basis to provide Tyr. It is therefore recommended not to use a Phe+Tyr requirement in the idealamino acid proile but to use a SID Phe:Lys of 54% and a SID Tyr:Lys of 40% to support maximal growth.

absent

La phénylalanine (Phe) et la tyrosine (Tyr) sont des acides aminés indispensables pour la croissance. La Tyr est fournie soit directement par l’aliment, soit indirectement par biosynthèse à partir de la Phe alimentaire. Les teneurs minimales dans l’aliment de Phe:Lys et en Tyr:Lys digestibles iléales standardisées (DIS) qui maximisent la croissance n’ont pas été estimées expérimentalement. Trois expériences ont été réalisées pour déterminer la réponse de porcelets entre 10 et 20 kg de poids vif à l’apport croissant de Phe:Lys DIS (33, 39, 46, 52, 58 et 65% ; expérience 1), de Tyr:Lys DIS (21, 27, 33, 39, 45 et 52% ; expérience 2) et à la substitution équimolaire de Tyr par la Phe (50, 43 et 36% de Tyr:(Phe+Tyr) DIS ; expérience 3). Pour chaque expérience, six animaux issus de 14 blocs ont été alimentés avec un des six régimes contenant 14,5% de MAT et 1,00% de Lys DIS et différant par l’apport de L‐Phe et/ou de L‐Tyr. La croissance est maximisée pour des teneurs en Phe:Lys DIS et Tyr:Lys DIS de, respectivement, 54 et 40%. Des déficiences de 10% en Phe et Tyr réduisent la croissance de, respectivement, 3,0 et 0,7%. La substitution équimolaire de Tyr par la Phe réduit quant à elle les performances d’environ 10%. En conclusion, il est recommandé de ne pas raisonner le besoin en Tyr exprimé par la somme de la Phe et de la Tyr, mais d’utiliser un ratio de 54% en Phe:Lys DIS et de 40% Tyr:Lys DIS pour maximiser la croissance., Phenylalanine (Phe) and tyrosine (tyr) are indispensable amino acids for growth. Tyrosine can be provided directly by the diet or indirectly by biosynthesis from dietary Phe. The standardized ileal digestible (SID) Phe:Lys and Tyr:Lys requirements have not been determined experimentally in piglets. Three experiments were conducted to estimate the response of piglets (10‐20 kg body weight) offered diets with different levels of SID Phe:Lys (33, 39, 46, 52, 58, and 65%; experiment 1), SID Tyr:Lys (21, 27, 33, 39, 45, and 52%; experiment 2) and the effect of equimolar substitution of Tyr by Phe (50, 43, and 36% SID Tyr:(Phe+Tyr); experiment 3). For each experiment, six pigs (originating from 14 blocks of six pigs each) were assigned to one of six low CP diets (14.5% CP) sublimiting in SID Lys (1.00%) and providing different levels of L‐Phe and/or L‐Tyr. The estimated SID Phe:Lys and SID Tyr:Lys for maximizing daily gain were 54 and 40%, respectively, using a curvilinear‐plateau model. A 10% deficiency in Phe and Tyr reduced daily body weight gain by 3.0 and 0.7%, respectively. The equimolar substitution of Tyr by Phe resulted in a reduced growth rate of about 10%. In conclusion, it is recommended not to express the Tyr requirement as the sum of Phe and Tyr, but rather to use specific ratios for each of these amino acids to maximize growth, i.e., 54% SID Phe:Lys, and 40% SID Tyr:Lys.

The use of crystalline amino acids allows reducing the CP in the diet without compromising performance. The extent to which the CP content in the diet can be reduced under practical conditions depends on accurate knowledge of the requirements of amino acids that may become limiting when pigs are offered low-CP diets. Valine is now considered the next-limiting amino acid after Lys, Met (+Cys), Thr, and Trp in cereal-soybean meal based diets. Nevertheless, experimental studies on the response of pigs to the Val supply are scarce. Our objective was to analyze studies for growing pigs fed diets with increasing levels of L-Val.

Session 2 : Energy and Protein Interaction: Monogastrics; absent

In poultry production, there is a constant need for updating birds' requirements especially protein and amino acids, because of economical purposes, genetic improvements and also because parameters of interest are changing from the classical ones i.e. body weight, feed conversion ratio, to more recent ones, i.e. meat yield and processing quality (Berri et al., 2008; Dozier et al., 2010). In chickens, these last characteristics are strongly influenced by the ultimate pH of the meat which depends on muscle glycogen content (Le Bihan-Duval et al., 2008). Recent observations suggest the possibility of modulating these characteristics by varying the lysine intake of broilers (Jlali et al., 2012). Our objective was to determine the digestible lysine requirements of male Ross broilers during the finishing period, taking into account birds growth, feed conversion, edible parts yields, adiposity and meat quality.

Session 53. Feed efficiency in non-ruminants; absent

Session : Environnement; Feed‐use amino acids (AA) allow reducing, at constant performance, the protein content of pig feeds and nitrogen excretion by the animals. The aim was to assess the environmental impact of one kg of live pig produced in a conventional farm in Brittany by Life Cycle Assessment (LCA) according to several scenarios of AA incorporation. Two modalities of effluent management (slurry or solid manure) and two hypotheses of protein sources (soybean only, or soybean, rapeseed and peas) were considered. In three scenarios, feeds were least cost formulated: no AA (NoAA‐Min€), AA incorporation and fixed protein content at CORPEN level (AACORP‐Min€), and AA with free protein content (AA‐Min€). In AA‐MinCP, feeds were formulated to minimize protein content. Fattening pigs were fed either with only one feed (1P), two feeds (2P) or according to multiphase feeding (MP). The protein content of pig feeds decreased with the amino acid incorporation, down to 123 g/kg in MP‐AA‐MinCP. At the same time, the incorporation of soybean meal into feeds decreased down to 70 kg/t in MP‐AA‐MinCP. With slurry management, AA‐Min€ reduced the impacts on climate change, acidification and eutrophication by at least 26%, 22% and 14% respectively. With solid manure management, AA‐Min€ reduced the impacts on climate change, acidification and eutrophication by at least 20%, 20% and 12% respectively. The impacts on terrestrial ecotoxicity, cumulated energy demand and land occupation were barely sensitive to the studied scenarios. Amino acid incorporation in least cost formulated feeds substantially reduced the feeding cost and environmental impacts of pig production.; Les acides aminés industriels (AA) permettent de réduire, à mêmes performances, les teneurs en protéines des aliments et l’excrétion d’azote par les porcs. L’objectif de l’étude était d’évaluer les impacts environnementaux du kg de porc vif produit en sortie d’un élevage conventionnel par Analyse du Cycle de Vie (ACV) selon différents scénarios d’incorporation d’AA. Deux modalités de gestion des effluents (lisier LIS et fumier FUM) et deux hypothèses de sources de protéines (uniquement soja (SOJ) ou soja, colza et pois (SOJCP)) ont été considérées. Trois scénarios sont formulés à moindre coût : pas d’AA (NoAA‐Min€), incorporation d’AA et taux de protéines CORPEN (AA‐CORP‐Min€), et AA avec taux de protéines libres (AA‐Min€). Dans le scénario AA‐MinCP, les aliments sont formulés en minimisant le contenu protéique. Les porcs charcutiers sont engraissés avec un aliment unique (1P), en biphase (2P) ou multiphase (MP). Le contenu protéique des aliments diminue avec l’augmentation de l’incorporation des AA, jusqu’à 123 g/kg pour MP‐AA‐MinCP. Parallèlement, les teneurs en tourteau de soja diminuent jusqu’à 70 kg/t pour MP‐AA‐MinCP. En modalité LIS, AA‐Min€ réduit les impacts sur le changement climatique, l’acidification et l’eutrophisation d’au moins 26%, 22% et 14% respectivement. En modalité FUM, AA‐Min€ réduit les impacts sur le changement climatique, l’acidification et l’eutrophisation d’au moins 20%, 20% et 12%, respectivement. Les impacts écotoxicité terrestre, demande en énergie et occupation des surfaces sont peu sensibles aux scénarios étudiés. L’incorporation d’AA dans des aliments formulés à moindre coût permet de réduire sensiblement les impacts environnementaux de la production porcine.

Session : Alimentation; A meta‐analysis was performed to estimate the tryptophan to lysine requirement ratio, on a standardized ileal digestible basis (SIDTrp:Lys),that maximises average daily gain (ADG), average daily feed intake (ADFI) and gain to feed ratio (G:F) of pigs between 25 and 120kg body weight. A database of87trials was established. The nutrient composition of diets was recalculated from feed ingredients and information from INRA tables. Among the trials, 13weredesigned to express the requirement relative to Lys (i.e., Lys was the second limiting factor after Trp) while testing at least four levels of Trp, and these trials were considered in the metaanalysis. The curvilinear‐plateau model was used to estimate the animal response to SID Trp:Lys. The estimated SID Trp:Lys requirements were20.9, 19.9 and 21.0%, for ADG, ADFI and G:F, respectively, with an average value of 20.6%. The response between 17 and 21% SID Trp:Lys levels was estimated to be +6.7 and +3.6%, for ADG and G:F, respectively.

Session : Alimentation; absent

When a diet deficient in Val with excessive Leu is offered to pigs, feed intake is reduced. The physiological mechanisms underlying the rejection of branched-chain AA (BCAA) unbalance are unknown. A meal pattern analysis was performed to determine how pigs respond to the ingestion of a diet unbalanced in BCAA to identify the mechanisms responsible for the aversive response of such a diet. Eight female pigs (initial BW of 30.7 +/- 1.7 kg at 9 wk of age) received alternatively a diet either unbalanced in BCAA supply (i.e., a diet deficient in Val with an excess supply of Leu) or a control diet (i.e., a diet with a sufficient supply of Val with an excess supply of Leu) during 4 periods of 5 consecutive days. Feed consumption was monitored continuously to determine feeding behavior. Average daily feed intake of pigs receiving the diet unbalanced in BCAA was l3% less than that in pigs offered the control diet (P < 0.01). Offering the unbalanced diet had no effect on meal size but reduced the number of meals from 9.9 to 8.5 per day (P < 0.01). There was no difference between diets in intermeal interval but a slight trend for an increased meal duration from 14.5 to 16.3 min in pigs receiving the unbalanced diet (P = 0.13). The rejection of feed appeared within the first 2 d after offering the unbalanced diet. The results of this experiment indicate that the BCAA unbalanced diet had no effect on satiety and satiation. After initiation of a meal, pigs ate a normal-sized meal and were hungry, but the increase in meal duration and a decrease in the number of meals inferred a negative alliesthesia (less pleasant) response to the BCAA unbalanced diet. On the basis of meal patterns, the rejection of a diet unbalanced in BCAA may not involve short-term mechanisms related to oropharyngeal and gastrointestinal receptors but may be triggered by postabsorptive signals.

Session : Alimentation; Histidine (His) and leucine (Leu) are essential amino acids for growth in piglets. A consequence of the reduction of the crude protein content of piglet diets by using L‐Lysine (Lys), L‐Threonine, DL‐Methionine, L‐Tryptophan and L‐Valine is that His and Leu may be limiting for growth, although information on the requirements for these amino acids is scarce. The objective of this study was to determine the effect of supplementing a low crude protein diet with L‐His and L‐Leu on feed intake and growth to estimate the His and Leu requirement of 10‐20 kg pigs. In each of four experiments, 14 blocks of six pigs each were allotted to six levels of, respectively, standardized ileal digestible (SID) His:Lys (20, 24, 28, 32, 36, and 40%), His:Lys (21, 24, 27, 30, 33, and 36%), Leu:Lys (70, 78, 86, 94, 102, and 110%), and Leu:Lys (80, 90, 100, 110, 120, and 130%). The estimated SID His:Lys and Leu:Lys requirements were respectively 32 and 102% for maximizing daily gain and 29 and 97% for maximizing feed efficiency using a curvilinear‐plateau model. When His and Leu levels were 10% below the requirement estimate, daily gain was reduced by 3%. The results of the present study indicated that the SID His:Lys and Leu:Lys requirements in 10‐20 kg pigs were determined to be 32 and 102%, respectively.

Improving the amino acid (AA) profile of the diet by using l-Lys, l-Thr, dl-Met, l-Trp and l-Val helps to reduce the dietary CP content, thereby reducing nitrogen excretion while maintaining the performance of pigs. Valine is the fifth limiting AA in cereal–soybean meal-based diets. The extent to which the CP content in the diet can be reduced further without compromising performance depends on the requirement of the next limiting AA. In cereal–soybean meal-based diets, Ile, His and Leu may be the limiting AAs after Val, although information on the requirements for these AAs is scarce. Six experiments were conducted to determine the effect of supplementing a low-CP diet with l-Ile, l-His and l-Leu on the performance of pigs weighing 10 to 20 kg. Experiment 1 was designed to determine the most limiting AA with respect to performance among Ile, His and Leu. A diet 10% deficient in Ile, Leu and His relative to the National Research Council (NRC, 1998) requirement estimates tended to decrease daily feed intake and daily gain by 6% and 8%, respectively. A 10% deficiency in His alone had no effect, whereas a 10% deficiency in Ile or Leu slightly reduced daily feed intake and gain. In the remaining experiments, the standardized ileal digestible (SID) Ile : Lys, His : Lys and Leu : Lys requirements were estimated. In Experiments 2, 3, 4, 5 and 6, 14 blocks of six pigs each were assigned to six levels of SID Ile : Lys (40%, 43%, 46%, 49%, 52% and 55%), His : Lys (20%, 24%, 28%, 32%, 36% and 40%), His : Lys (21%, 24%, 27%, 30%, 33% and 36%), Leu : Lys (70%, 78%, 86%, 94%, 102% and 110%) and Leu : Lys (80%, 90%, 100%, 110%, 120% and 130%), respectively. Across experiments, the estimated SID Ile : Lys, His : Lys and Leu : Lys requirements for maximizing daily gain were 49%, 32% and 102%, respectively, using a curvilinear plateau model. When Ile, His and Leu levels were 10% below the requirement estimate, daily gain was reduced by 9%, 3% and 3%, respectively. The results of this study indicate that the Ile requirement estimate is lower than the current NRC requirement estimate, whereas the Leu and His requirements correspond to those proposed by the NRC.

What are the reasons for the variability of pig responses to dietary tryptophan supply?. CLANA

National audience; The branched‐chain amino acids (BCAA: valine, leucine, isoleucine) are among the next‐limiting amino acids for growth in piglets after Lys, Thr, Met+Cys and Trp. To formulate low crude protein diets, a clear understanding of the BCAA requirement (e.g. Ile) is required. Most studies dealing with the Ile requirement use blood cells as a protein source, which has a very low Ile content and high or very high Leu and Val contents. However, the BCAA share the first two steps of their catabolism and an excess of one BCAA may affect the availability of the other BCAA. The objective of this study was to determine the Ile requirement with a diet morebalanced in BCAA. A dose‐response study was carried out with 14 blocks of 6‐week‐old piglets (11 kg initial body weight). Each piglet within a bloc was allotted to one of six levels of standardized ileal digestible (SID) Ile:Lys (40, 43, 46, 49, 52, 55%) and performance was monitored for three weeks. Requirement for maximum growth rate and feed conversion ratio were estimated, respectively, at 47 and 45% SID Ile:Lys using a linear‐plateau model and at 49 and 47% SID Ile:Lys using a curvilinear‐plateau model. For diets without an excess supply of BCAA, the Ile requirement may be as low as 49% SID Ile:Lys in post‐weaned piglets. With the currently available crystalline amino acids, this recommendation allows further reduction of the crude protein content in piglet diets.