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L'etude des effets d'un taux suboptimal de lysine dans le regime sur la consommation spontanee d'aliment, les performances de croissance et la composition corporelle, chez le porc en finition, a fait l'objet d'une experience realisee sur 60 animaux des 2 sexes, femelles et mâles castres, entre 63 et 103 kg de poids vif. Ces derniers sont affectes, par la methode des blocs, a 3 traitements, selon la teneur en lysine et le mode d'alimentation, pour une teneur en matieres azotees ajustee a 15%. Dans le traitement temoin 1, les animaux femelles et mâles castres recoivent respectivement 0,64 et 0,58% de lysine, taux differencies selon leurs besoins. L'effet d'un apport suboptimal de lysine (15% en dessous du temoin: 0,54 et 0,49% respectivement pour les femelles et les mâles castres) est analyse soit en alimentation a volonte (traitement 2), soit en ajustant le niveau d'alimentation sur celui du temoin (traitement 3) a l'interieur de chaque bloc, sur la base du poids metabolique (poids vif, kg 0,75 ). Les resultats montrent qu'un apport suboptimal de lysine ne modifie pas significativement le niveau d'ingestion d'aliment, qu'il soit exprime en quantite moyenne journaliere ou par kg de poids metabolique. Il s'ensuit que la reduction du gain ponderal (-7,6%) s'accompagne d'une legere augmentation de l'etat d'adiposite des carcasses a l'abattage (diminution du rapport tissus maigres/tissus gras). L'application aux animaux recevant un aliment deficitaire en lysine d'un plan de rationnement correspondant au niveau d'ingestion a volonte par les animaux recevant un taux optimal de lysine a provoque une restriction alimentaire (-11 %), accentuant l'effet depressif sur la croissance (-12%). Les variations resultant des apports de lysine et d'aliment exercent des effets independants et additifs sur la croissance ponderale, les gains de tissus maigres et gras etant determines respectivement par la consommation de lysine et celle d'aliment. Le probleme de l'alimentation egalisee entre traitements a un niveau correspondant a celui de l'alimentation a volonte est discute

An experiment involving 110 crossbred pigs (Pietrain x Large White) was conducted in order to evaluate the requirement for digestible lysine during the finishing period. Two periods were considered: 50 to 80 kg live weight and 80 to 110 kg live weight, with 50 pigs (25 castrated males and 25 females) in each of them. Ten additional pigs were slaughtered and dissected at 50 kg live weight in order to estimate the initial body composition of experimental animals. Five increasing levels of lysine supply were tested for each period and gender. From 50 to 80 kg, average daily gain (ADG) increased linearly with lysine supply whereas a linear-plateau response was measured from 80 to 110 kg, up to a maximum response of 930 g/d for a supply of 17.2 g digestible lysine per day. For a same daily supply of lysine, ADG and feed conversion ratio (FCR) were 50 g/d and 0.5 kg/kg higher during the second than during the first period, respectively. ADG increased by 37.9 g/d, FCR decreased by 0.16 kg/kg and average daily muscle gain increased by 29 g per g of supplementary digestible lysine. For the genotype involved and the feeding level achieved in our experiment, it was concluded that the requirement for digestible lysine decreased from about 0.80 g/MJ net energy at 50 kg to 0.63 g/MJ at 100 kg live weight. The marginal efficiency of digestible lysine was around 65–70%. This value can be used for a factorial estimation of the requirement, based on daily protein deposition. More empirical predictive equations, based on ADG or muscle gain, are also proposed.

Three experiments were conducted with 188 finishing pigs (females and castrated males) of the Large White breed, between mean body weights (BW) of 53 and 88 kg, and fed according to a feeding scale, to study the effects of dietary tryptophan (TRP) deficiency (0.10 vs. 0.13%) on feed intake, growth performance, body composition and tissue gain, and meat quality, according to age or BW at slaughter or BW gain. TRP deficiency depressed feed intake, growth performance, and tissue (muscle and fat) gains, with less pronounced effect with advancing age. Females were more sensitive to TRP deficiency than castrated males. The weights of lean and fat joints both decreased with TRP deficiency in pigs slaughtered at the same age, with no resulting change in carcass composition, while they were similar to those in control animals after slaughter at the same BW. The addition of dietary limiting TRP affected carcass conformation through preferential stimulation of development in depth (forehand, hindquarter) compared to development in length, thus producing longer carcasses at the same age at slaughter, but shorter carcasses when pigs were slaughtered at the same BW. This was also the case after feed restriction, for similar gain as in TRP-deficient animals. There was no effect of dietary TRP on muscle quality characteristics. The results were discussed in relation to the common stimulating effect of the limiting dietary factor for growth, whether amino acid or energy, on the development of the early maturing body compartments and the resulting changes in carcass conformation according to age or weight at slaughter.

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La production porcine a bénéficié, au cours des dernières décennies, de progrès importants et continus réalisés par la sélection pour une croissance sans cesse plus forte de tissus maigres et un dépôt décroissant de gras, en réponse à la demande des consommateurs. Cet article examine les changements intervenus dans l’alimentation en considérant les évolutions récentes et les perspectives, compte tenu de l’évolution prévisible des performances de production et de l’apport des nouvelles technologies. L’importance du progrès génétique en faveur de la croissance des tissus maigres a conduit en premier lieu à envisager une modélisation de la prévision des besoins nutritionnels (énergie, protéines et acides aminés, minéraux), dont les variations se traduisent notamment par des exigences moins marquées en énergie que par le passé et par un accroissement important des besoins en acides aminés relativement à l’apport énergétique. Grâce à cette démarche de modélisation, il est désormais possible de définir de nouvelles stratégies d’alimentation adaptées pour la production de viande maigre (plan de rationnement alimentaire, choix du type d’aliment pour une phase de production déterminée), en fonction des conditions particulières de production et à l’aide de systèmes d’évaluation des aliments suffisamment discriminants (énergie nette, digestibilité iléale des acides aminés). En outre, l’augmentation de certains intrants alimentaires (azote, phosphore) pour une production accrue de viande maigre implique une gestion raisonnée de leurs apports, afin de prévenir des rejets excessifs dans l’environnement (eau, atmosphère). La tendance à une certaine dégradation de la qualité de la viande, notamment sous l’angle technologique et organoleptique, au fur et à mesure des progrès de la sélection sur la croissance musculaire, oblige à une prise en compte, par l’alimentation, des exigences de qualité des produits, qu’il s’agisse des dépôts gras ou des tissus maigres (importance du gras intramusculaire). Il en est de même avec le recours à de nouvelles technologies permettant, soit de préserver le potentiel de croissance musculaire (utilisation du porc mâle entier), soit de le stimuler (facteurs de croissance). En dernier lieu, après avoir considéré les effets de l’alimentation sur la conformation des carcasses, en relation avec l’amélioration du développement musculaire, les conséquences d’un amaigrissement excessif des truies sur les performances de reproduction sont évoquées en liaison avec la mobilisation et la reconstitution des réserves lipidiques corporelles. Ce problème d’équilibre entre les tissus musculaire et gras constitue un enjeu important pour l’évolution future de l’alimentation du porc maigre. Au plan de l’application, les nouvelles approches nutritionnelles, basées sur l’établissement de lois de réponse qui prennent en compte la diversité à la fois des types génétiques (depuis les plus gras jusqu’aux plus maigres) et des conditions d’élevage et de milieu devraient permettre, dans chaque cas, de définir les conditions optimales de production d’un type de porc particulier., During the last decades, pig production has gained important and continuous progress from selection for constantly increasing lean tissue gain and decreasing fat deposition, in order to meet the increasing demand of market and consumer. The present report is intended to examine the changes that have been introduced in pig feeding to bring the necessary adaptations for optimizing growth performance, by considering the recent development and the trends for the future, in relation to the predictable shift in production performance and technological innovations. The unceasingly changing contribution of animal related factors has made it necessary to consider prediction modelling of nutritional requirements (energy, protein and amino acids), with a general trend to lower energy needs than in the past and higher amino acid requirements relative to energy. This modelling approach allows to implement new feeding strategies (feeding scale, type of feed for a given phase of production) that are adapted to lean meat production, according to specific production conditions and with sufficiently discriminating feed evaluation systems (net energy, ileal amino acid digestibility). In addition, the steady increase in some dietary inputs (nitrogen, phosphorus) for expanded lean meat production implies a sound management of nutrient supply, in order to prevent excessive loss to the environment (water, atmosphere). The observed trend to some degradation of meat quality with intense selection for muscular growth, particularly with regard to technological and organoleptic characteristics, necessitates to take into account these constraints in feeding, whether one considers fat deposition or lean tissue gain (extent of intramuscular fat). Finally, after examining the effects of feeding on carcass conformation, we have considered the incidence of excessive leanness in sows on reproduction performance, in relation to mobilization and restauration of body lipid reserves. This problem of optimum balance between lean and fat is an important challenge for future evolution of feeding lean pigs. From practical standpoint, the new nutritional approaches based on establishing dose - response relationships that integrate the diversity of available genotypes (from the fattest to the leannest), along with production and environmental conditions, should contribute, in each case, to fix the optimum conditions for producing a given type of pig.

Different energy values are given to a given feed according, firstly, to the considered step of energy utilization by the pig (digestible (DE), metabolizable (ME) or net (NE) energy) and, secondly, to the prediction method used for each step. The aspects developed in the first part of this review relate to the effects of chemical composition of the diet and animal factors such as physiological stage or body weight, and also the interactions between diet and animal, on digestive and metabolic utilization of energy. In a second part, the available DE, ME and NE systems when applied to diets or ingredients are presented. In the third part, the different energy systems (firstly DE vs. ME vs. NE, and secondly the NE systems) are compared in terms of advantages, limits and applicability for each of them. The comparison indicates that the hierarchy between diets and, more clearly, between ingredients is markedly dependent on the energy system. The composition of diets (ingredients and chemical characteristics) resulting from least-cost formulation is also affected by the energy system. The last part of the review considers the validity of the different energy systems or their ability to predict pig performance. From this review, it is clear that more emphasis should be given to, firstly, study digestive interactions and, secondly, improve the methods (chemical, physical, in vitro, …) used for (rapid) prediction of energy values of pig feeds.

Self-selection of dietary lysine was studied in one 42-d experiment involving 100 Large White growing pigs, with an equal number of females and castrated males, initially weighing 17.7 kg, within 5 treatments of 20 animals in each. A common basal diet (17% CP, 13.8 MJ DE/kg) based on maize, soybean meal and peanut meal, and containing a deficient level of lysine (0.61%), was used. Supplementary L-lysine was provided to obtain suboptimal (0.74%), optimal (0.85%) and superoptimal (1.21%) levels of total lysine for growth, as assumed from usual recommendations. In addition to treatment 1, a control where pigs were fed ad libitum a single diet with 0.85% lysine, 4 treatments with free choice of lysine within paired diets were compared. These included deficient or suboptimal levels of lysine on the one hand and optimal or superoptimal levels on the other according to a 2 x 2 factorial plan: 0.61 vs 0.85% (treatment 2), 0.74 vs 0.85% (treatment 3), 0.61 vs 1.21% (treatment 4), 0.74 vs 1.21% (treatment 5). The results showed sex difference in diet selection according to lysine content. Females had a distinct preference for the superoptimal level (1.21%) compared to the optimal level (0.85%), especially during the initial period of the trial, their requirement being higher than the presupposed 0.85% optimal level. For castrated males, the preference for lysine was restricted to the lower 0.85% level. The ability of females to self-select a greater proportion of the high lysine feed as opposed to castrated males was related to a higher potential for lean tissue growth. These results confirm that the growing pig is able to differentiate between diets differing only in their lysine contents. Complementary observations on plasma-free amino acids suggested the use of diets adequately balanced for amino acids when offered for free choice.

Cet article traite des données récentes sur les relations d’équilibre entre les acides aminés dans l’alimentation du porc en croissance, au travers du concept de la protéine "idéale". Après avoir précisé les limites de ce concept, sur le plan de la constance des rapports entre les teneurs en acides aminés indispensables et celle en lysine, prise comme référence, sont considérés les ratios entre les acides aminés limitants secondaires (tryptophane, thréonine, méthionine et acides aminés soufrés) et la lysine, compte tenu des spécificités de leur rôle fonctionnel au plan métabolique et physiologique. Pour cela, l’incidence des écarts entre le profil de composition en acides aminés de la protéine alimentaire et celui de la protéine idéale (excès de protéines) sur l’ingestion alimentaire et les performances de croissance est étudiée selon la nature de l’acide aminé le plus limitant. En raison de sa faible contribution aux processus métaboliques autres que ceux concernant la synthèse de protéines corporelles, la lysine constitue une référence stable pour l’expression des rapports entre les acides aminés. A la différence de la lysine, le tryptophane interagit fortement et négativement avec les protéines excédentaires (acides aminés neutres de grande taille) au niveau de l’appétit et de la croissance, en liaison avec un dysfonctionnement du système sérotoninergique. Ceci met en défaut la constance du rapport tryptophane / lysine, qui devrait être corrigé sur la base d’un ratio minimum tryptophane / acides aminés neutres de 4 %, pour se prémunir d’un risque d’excès de ces derniers dans certaines protéines alimentaires. Dans le cas de la thréonine, lorsqu’elle est limitante, il ressort une interaction positive avec les acides aminés non indispensables (acide glutamique). L’équilibre méthionine / cystine a été reconsidéré en fonction des données récentes de la bibliographie. En conclusion, les recommandations concernant les rapports acides aminés / lysine pour le porc en croissance ont été réactualisées., The present review was intended to provide recent information on the relationships between dietary amino acids in growing pigs, through the concept of “ideal” protein. The limits of this concept were given, namely with regards to the constant ratios between essential amino acids and lysine, as a reference. The ratios between secondary limiting amino acids (tryptophan, threonine, methionine and sulphur amino acids) and lysine were considered, according to their specific functional role in metabolic and physiological processes. For this purpose, the effects of the deviations between amino acid profiles of dietary and ideal protein (excess protein) on voluntary feed intake and growth performance were investigated, in relation to the most limiting amino acid. Owing to its poor contribution to metabolic processes, lysine is a stable reference for expressing ratios between essential amino acids. Unlike lysine, dietary tryptophan interacts heavily and negatively with excess protein (large neutral amino acids), through brain serotonin dysfunction, in relation to depressed appetite and growth. In practice, the tryptophan / lysine ratio should not be considered as a constant. It should be corrected on the basis of a minimum ratio between tryptophan and large neutral amino acids of 4 %, in order to prevent an eventual risk of their excess in some dietary protein. In the case of threonine, when it is limiting, a positive interaction with non essential amino acids (glutamic acid) was reported. Dietary balance between methionine and cystine was re-evaluated in accordance with the recent data from literature. To conclude, the revised essential amino acid to lysine ratios for the growing pig were given.

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Some of the results of an experiment on the breed x nutritional environment interaction effect on performance traits of the growing pig are briefly reported. The breeds involved are two double muscled breeds (Pietrain and Belgian Landrace) and a control breed with a normal conformation (French Landrace). Nutritional variations consist of a 10% increase of the digestible energy concentration and a 27% increase of the ratio of crude protein to digestible energy in the diet offered ad libitum. Breed means, pooled over the diets, are given for a number of trait, including the dynamics of muscle growths digestibility of dietary nutrients and nitrogen retention. Pietrain and Belgian Landrace pigs show a similar degree of muscular hypertrophy and are markedly better than French Landrace pigs in carcase muscle content (+5 percentage points). However, as the Pietrain and the Belgian Landrace greatly differ in terms of lean tissue growth rate, the responses of pigs from these two breeds to the nutritional variations also differ in some aspect, though not to a large extent.

Eight replicates of four Large White littermate female pigs were used to evaluate the effect of protein and lysine levels in the diet on the efficiency of protein and energy utilization. In each replicate, one pig was slaughtered at about 20 kg live weight and the others received three diets that contained (per Mcal digestible energy) 37.5 and 2.00 g (diet pl), 37.5 and 2.35 g (diet pL) or 45.0 and 2.35 g (diet PL) of digestible protein and lysine, respectively. Pigs were slaughtered after a 7-wk period. Tissue and chemical composition of the gain and energy and nitrogen gain were determined by using the comparative slaughter technique. Metabolizable energy (ME) intakes were similar in the treatments. Pigs fed the pl diet had a smaller body weight and muscle gain and retained less nitrogen and more lipids than pigs fed pL and PL diets. The decrease in the level of nonessential nitrogen in the diet (pL vs PL) did not affect body weight and muscle gain and the amount of nitrogen retained in muscle tissues. However, pigs given the PL diet had a higher total nitrogen retention and a lower fat deposition and exhibited a higher heat production. For each gram of additional protein catabolized for energy purposes (PL vs pL), heat production was increased by 1.8 kcal. The amount of lysine per unit of muscle gain (38 g/kg) or protein deposited (120 g/kg) was independent of protein and lysine levels in the diet. Estimates of energy (indirect calorimetry) and nitrogen (balance technique) retention were also obtained on the same animals; results were comparable with data obtained by direct measurements.

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1. The associative effects of two fibre sources on ileal and overall digestibility of amino acids, energy and cell-wall components were studied by comparing wheat bran and soya-bean hulls in semi-purified diets given to growing pigs.2. Castrated male pigs were prepared with ileo-rectal anastomosis to measure ileal digestibility, and overall digestibility was measured in pigs without anastomosis.3. The three diets contained 190 g total fibre/kg dry matter (DM), derived from each fibre source or from a mixture of both fibre sources, so that each source provided half the amount of total fibre, and 170 g crude protein (nitrogen x 6·25)/kg DM by additions of casein.4. The effects of fibre sources on the ileal digestibility of amino acids were additive for most amino acids; the only significant interactions were found for threonine, methionine and aspartic acid. In contrast with ileal digestibility, systematic negative interactions between fibre sources on overall digestibility of amino acids were noted.5. There was no interaction between fibre sources in their effects on the digestibility of energy or of cell-wall components, irrespective of the site of digestion. The digestibility values were higher with soya-bean hulls than with wheat bran, especially at the faecal level.6. It is concluded that ileal digestibility of amino acids provides a better estimate of amino acid availability, as ileal measurements allow a better discrimination between diets than faecal measurements when distinct fibre sources are used alone or in combination at the same total fibre content. In contrast, for energy, the measurement of digestibility at both faecal and ileal levels permits the estimation of the partition of available nutrients between the small and large intestines.

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