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This paper reviews the available knowledge on nutritional requirements of non-surgically castrated male pigs to promote their potential for higher feed efficiency while ensuring low risk of boar taint and good carcass and meat qualities. Reasons for giving entire males ad libitum access to diets enriched with amino acids to satisfy their high potential for protein deposition are presented. This also applies to immuno-castrated male pigs, which can be fed like entire males until the second vaccination. Then their requirements for essential amino acids decrease significantly and supplies can be reduced accordingly. As boar taint is a crucial issue when producing entire male pigs, effects of incorporating various feed ingredients to reduce skatole level are discussed in terms of their efficacy and mode of action. With a low carcass adiposity, entire males have a lower intramuscular lipid content than females and barrows, which decreases the organoleptic quality of the meat. In addition, adipose tissues whose fatty acids may be highly unsaturated modify the technological aptitude of processed-and dry cured products. Accounting for these criteria in quality specifications of products may have impact and induce changes on the nutritional recommendations.

The practice of weaning at 21 days of age has developed considerably in France. The objective of this trial was to study the impact of the age of piglets at weaning (at 21 or 28 days of age) on pig health after weaning under normal or degraded conditions of live. The study was performed in experimental facilities on two batches of 252 piglets from weaning until seven weeks after weaning. A feeding practice with a secure feed during the first 7 days of post-weaning was implemented for pigs weaned at 21 days. Mortality rate was recorded, and diarrhea was assessed by analyzing fecal scores and measuring the dry matter content of the feces. Blood was collected from 160 piglets (to analyze the complete blood count, haptoglobin, antioxidant defense and the production of reactive oxygen species. During the post-weaning period, 47% of piglets were observed to have diarrhea on at least one day, and this percentage was not significantly influenced by age at weaning. The piglets weaned at 21 days of age had a 7-day lag in the onset of diarrhea compared to those weaned at 28 days of age. Animals weaned at 21 days under normal conditions have a higher mortality rate than those weaned at 28 days but not under degraded conditions. These results should be confirmed by other studies.

This paper reviews the available knowledge on nutritional requirements of non-surgically castrated male pigs to promote their potential for higher feed efficiency while ensuring low risk of boar taint and good carcass and meat qualities. Reasons for giving entire males ad libitum access to diets enriched with amino acids to satisfy their high potential for protein deposition are presented. This also applies to immuno-castrated male pigs, which can be fed as entire males until the second vaccination, when their requirements for essential amino acids decrease significantly. As boar taint is a crucial issue when producing entire male pigs, effects of incorporating various feed ingredients to reduce skatole and indole levels are discussed in terms of their efficacy and mode of action. With a low carcass adiposity, entire males have a lower intramuscular lipid content than females and barrows, which decreases the organoleptic quality of the meat, and adipose tissues whose fatty acids may be highly unsaturated, which modifies the technological aptitude of dry cured products., Quelles stratégies alimentaires pour couvrir les besoins nutritionnels des porcs mâles entiers et/ou immuno-castrés et pour réduire les risques d'odeur de verrat dans la viande ? Cet article fait le point sur les connaissances relatives aux besoins nutritionnels des porcs mâles non castrés chirurgicalement, dans la perspective de favoriser leur potentiel pour une meilleure efficience alimentaire, tout en veillant à maintenir un faible risque d'odeurs de verrat et à préserver les qualités de la carcasse et de la viande. Les raisons pour lesquelles une alimentation à volonté des mâles entiers, avec des aliments plus concentrés en acides aminés, doit être privilégiée, sont présentées, notamment pour optimiser leur potentiel de développement de la masse protéique. Elles s'appliquent également aux porcs mâles immuno-castrés, qui peuvent être nourris comme les mâles entiers jusqu'à la deuxième vaccination. Au-delà, leurs besoins en acides aminés essentiels sont nettement inférieurs à ceux des mâles entiers. Le risque d'odeur de verrat de la viande étant un problème crucial à maîtriser dans la production de mâles entiers, les impacts de l'incorporation de divers ingrédients alimentaires susceptibles de réduire les teneurs en scatol et indole sont discutés, tant pour ce qui concerne leur efficacité que les mécanismes mis en oeuvre. Avec une très faible adiposité de carcasse, les mâles entiers présentent, d'une part, une teneur en lipides intramusculaires inférieure à celle des femelles et des mâles castrés chirurgicalement, qui pénalise la qualité organoleptique de la viande et, d'autre part, un tissu adipeux dont les acides gras peuvent être fortement insaturés, ce qui modifie l'aptitude technologique au séchage des produits. What kind of feeding strategies should be used to meet nutritional requirements of entire male pigs and or immuno-castrated pigs and to reduce the risk of boar taint in meat?

The criteria for growth and feed efficiency are based on monitoring weight gain, regardless of its tissue composition. However, since carcass value is based essentially on its muscle content, the objectives of this study were to develop criteria related to the mass of muscle deposited, and then to test them on data from a pig trial. First, the limits of using the classification criterion “Lean Meat Percentage” in animal-production trials are explained. Then, replacing it with carcass muscle content based on scanner measurements is described. Measuring muscle mass by computed tomography or dissection allows average daily muscle gain (ADGm) to be calculated and the feed conversion ratio to be expressed per kg of muscle gain (ICm). These new criteria were compared to the usual ADG and IC criteria based on results obtained from pigs subjected to feed restriction (RA) compared to those with an ad libitum control diet. For the RA strategy, the relative difference (as a percentage of the control) was not significant for ICm, while it was negative for IC (-10.5%; P < 0.01). These results show the relevance of introducing animal-production criteria as a function of muscle mass to better assess effects of the feeding strategy. The additional cost of tomography can be limited by scanning only a subsample. Accurate measurement of body composition should be an integral part of animal-production trials in general and precision-breeding studies in particular., Les critères de croissance et d’efficacité alimentaire sont fondés sur le suivi du gain de poids, sans tenir compte de sa composition tissulaire. Or, la valorisation de la carcasse repose essentiellement sur sa teneur en muscle. Les objectifs de cette étude sont de proposer des critères rapportés au kg de muscle déposé, puis de les tester sur les données d’un essai porcin. Au préalable, sont expliquées les limites de l’utilisation du critère de classement (TMP) dans les essais zootechniques. Puis, il est proposé de lui substituer la teneur en muscle de la carcasse (TMC) en utilisant un scanner. Mesurer la masse musculaire par tomodensitométrie ou par dissection permet de calculer le gain moyen quotidien de muscle (GMQm) et l’indice de consommation exprimé par kg de gain de muscle (ICm). Ces nouveaux critères sont comparés aux critères habituels de GMQ et IC à partir des résultats obtenus chez des porcs soumis à une restriction alimentaire (RA) en comparaison avec une alimentation témoin à volonté. Pour la conduite RA, la différence relative (en % du témoin) est non significative pour l’ICm, alors qu’elle est négative pour l’IC (-10,5% ; P < 0,01). Ces résultats montrent la pertinence d’introduire des critères zootechniques rapportés au kg de muscle pour mieux évaluer l’incidence de la conduite alimentaire. Le surcoût lié à la tomographie peut être limité en ne scannant qu’un sous-échantillon. La mesure précise de la composition corporelle devrait faire partie intégrante des essais zootechniques en général et des études sur l’élevage de précision en particulier.

International audience; Suboptimal resource utilization due to outdated building standards, control systems and barn management approaches results in high emissions and losses within EU pig production. Additionally, with increasing concern for animal welfare, pig farmers are struggling to maintain competitiveness. The PigSys project addresses these issues by considering a whole system improvement towards a future sustainable and animal friendly pig production. The developed data warehouse platform is accessible to end-users to collect information on building characteristics and data from on-farm equipment, to connect them with a decision support system (DSS based on a bioclimatic model called ThermiPig). The DSS simulates the thermal balance and climatic conditions of a fattening room depending on a farmer’s decisions. A system using deep learning and machine vision techniques was developed to monitor pig behavior, providing a tool for early warning of problems related to pig welfare and health. New sensor data was used to evaluate level of noxious gases that impact pig performance and welfare. Pig cooling with showers over the slatted area and increasing air velocity at pig lying area were cost-effective options improving hygiene and mitigating ammonia emissions, both being crucial for improved environmental and social acceptability. Models to assess the trade-offs between environmental and bio-economic impacts of different pig housing and manure management were developed.

International audience; The dynamic model ThermiPig was developed to simulate thermal balance at the fattening room scale, as the result of the heat produced by the group of pigs or provided by incoming air and equipment and that lost due to air renewal or thermal conductivity of the walls and ceiling. A growth model (assuming thermoneutral conditions, InraPorc) and a bioclimatic model (ThermiSim) were combined to create ThermiPig. It considers a common time step (1 hour), definition of the pig thermoneutral zone (based on body weight and type of floor), evaluation of impacts of cold and hot exposure on the amount of available energy for growth, and the circadian distribution of heat produced daily by each pig (based on meal partition over the day and post-prandial thermic effect of feed). Data collected in vivo from a group of 96 pigs of the IFIP experimental station were used to evaluate the accuracy of the prediction of ambient temperature (T). Characteristics of the fattening room, regulation rules of the climate box control of the ventilation system, nutritional characteristics of the 2-phase feeding sequence, and outdoor conditions (hourly T and relative hygrometry) observed during the in vivo trial were used as inputs of the model, and simulation were performed on 30 virtual groups of pigs from the same genders and crossbreed. With average in silico growth performance of the 30 groups similar to observed ones, the error of prediction (RMSEP) on ambient T averaged 0.6°C. Thereafter, ThermiPig was used to simulate the impacts of alternative regulations for ventilation or the use of new equipment (heater, pad cooling) on growth performance of pigs, N excretion, and indirect energy (from feed intake) and direct energy (from electricity consumed by equipment) consumption. Comparison of multi-criteria performance in silico helps identify the most interesting option. Economic performance depends on carcass value minus costs of feed intake and electricity (depending on the energy source). Therefore, more accurate prediction of carcass value is expected in the next version of the model by considering effects of ambient temperature on the distribution of body fat and protein metabolism.

International audience; A mechanistic, dynamic and determinist model, called ThermiPig, has been developed by combining a growth model and a bioclimatic model. It allows for the prediction of the within-room thermal balance at the room level and its consequences on the daily and individual performance of group-housed pigs. As this research is part of the Pigsys ERA-Net project, co-funded under EU Horizon 2020 RI program (SuSan, www.era-susan.eu, Grant Agreement n°696231) by the French ANR (grant n°ANR-16-SUSN-0003-02), a survey was performed in different European countries by the partners of the project in order to describe different types of fattening rooms, feeding strategies and climatic conditions. Afterwards, the objective of the study was to use the results of the survey and to combine different characteristics of the fattening room (insulation, cooling and/or installed heater capacity when available, regulation rules of the climate control box) to simulate the corresponding impacts on (i) the thermal balance at room scale, (ii) growth performance, (iii) direct and indirect energy use, and (iv) nitrogen output in pigs. Simulations were performed over the whole fattening duration with each combination using 30 virtual batches of pigs, generated from an average animal growth profile. Based on outputs of the model, it is possible to evaluate the influence of insulation of walls or heater capacity under different climates or to optimize regulation rules of the climate box control of the ventilation system in terms of feed efficiency, margin on feed cost and nitrogen output.

International audience; Pigs in the EU are commonly reared in climate-controlled systems mainly dependent on air ventilation based on a single point (one sensor) temperature set value. These systems assume even spatial distributions of the indoor climate. Since pigs are sensitive to both temperature and other environmental aspects such as humidity and noxious gas concentration, adverse climate conditions can decrease animal welfare and consequently lead to economic losses. In an on-farm study, we measured temperature, relative air humidity, air velocity, ammonia and carbon dioxide concentrations continuously on five different measuring points in one room for a total of three consecutive batches (672 pigs per batch). Fresh air was supplied through ceiling diffuse inlet by a negative pressure ventilation system with two exhaust air ducts which were automatically controlled by the climate control unit The animals were continuously monitored using four network cameras (CCTV) during the whole batches (growing period). Deep learning techniques were developed to automatically detect the activity level of the animals in the recorded video data. Severe spatial differences (horizontal and vertical) in environmental conditions between the measurement points and temporal changes within and across batches were observed, which directly affected the animals’ activity levels. The results demonstrate that environmental control based on single point measurements can have severe shortfalls. Furthermore, environmental information beyond air temperature need to be integrated into climate control to assure appropriate conditions for the animals' health and welfare.

International audience

Growth performance of pigs obtained with three feeding strategies were compared. Strategies ALA, ALB and RAA differed by the feeding level (AL: ad libitum, RA: restricted at 85% AL) and the 3-phase feeding sequence that met amino acid requirements or not (subscripts A and B, respectively). Two batches, each with four pens of six gilts or barrows per treatment, were used. Carcass leanness was 1.5 percentage point higher in RAA than in ALA (62.4 vs 60.9, P > 0.01) on average from both batches. The feed conversion ratio (FCR) was similar in both treatments in batch 1 (2.46 vs 2.40), but it increased in RAA in batch 2 (2.56 vs 2.39, P < 0.05). This difference may be related to the housing conditions during batches 1 and 2 (studied in winter and summer, respectively). Hence, daily feed intake (DFI) of ALA was 20% lower in batch 2 than in batch 1. Therefore, DFI of RAA in batch 2 was 28% lower than that of ALA in batch 1. With sequence B, FCR was higher than that of sequence A, and the difference was larger in gilts than in barrows (interaction: P < 0.01). The decrease in carcass leanness was also larger in gilts, especially under warm conditions (batch 2). This study demonstrated that both FCR and carcass leanness are improved by more adequate AA nutrition. Carcass leanness was also improved by restricting feed, which was associated with a longer fattening duration. Precise grading of the entire carcass or its main cuts would help to assess more accurately consequences on the commercial value that may attenuate the extra cost of production due to the longer fattening duration., L’étude compare les performances des porcs en croissance alimentés suivants trois stratégies (ALA, ALB et RAA) qui diffèrent par le niveau d’alimentation (AL : ad libitum ; RA : rationné à 85% de AL) et la couverture des besoins en acides aminés ou pas par une séquence triphase (respectivement notées A et B en indice). Deux bandes sont utilisées avec chacune quatre cases de six femelles ou six mâles castrés par stratégie. Le rationnement permet d’augmenter le taux de muscle des pièces (TMP) de 1,5 point (RAA : 62,4 vs ALA : 60,9, P < 0,01) en moyenne pour les deux bandes. L’indice de consommation (IC) reste stable avec le rationnement dans la bande 1 (2,46 vs 2,40) mais augmente dans la bande 2 (2,56 vs 2,39, P < 0,05). Cela s’explique sans doute par les conditions d’élevage des deux bandes, étudiées respectivement en périodes hivernale et estivale. Ainsi, la consommation moyenne journalière (CMJ) du lot ALA de la bande 2 est inférieure de 20% à celle du lot ALA de la bande 1, d’où une CMJ du lot RAA de la bande 2 inférieure de 28% à celle du lot ALA de la bande 1. La séquence B dégrade l’IC de façon plus importante chez les femelles que chez les mâles castrés (P < 0,01). Une dégradation plus marquée du TMP apparaît également chez les femelles élevées en situation de stress thermique (bande 2). Cette étude confirme l’intérêt de couvrir les besoins en acides aminés pour améliorer l’IC et le TMP. Le rationnement permet également d’obtenir un gain sur ce critère, mais au prix d’un engraissement plus long. Une évaluation plus fine de la qualité de la carcasse et des pièces devrait permettre de mieux quantifier l’incidence sur la valeur commerciale susceptible de compenser le surcoût de production.

National audience

International audience; Due to the relative high mineral phosphate cost and the consequences of phosphorus supplied in excess on the environment, a strong trend towards improved adequacy between its supplies and requirements has been observed for a while in reproductive sows. Conversely, calcium mineral sources are relatively cheap, and the dietary calcium level is not limited by any regulation. As calcium and phosphorus interact in the digestive tract and in their metabolism, their supplies need to be balanced. Based on available literature on phosphorus (large) and calcium (scarce), a model was developed that assesses calcium requirements in reproductive sows. Due to difficulties in the assessment of the degree of bone mineralization in practice, the present version of the model cannot be used to simulate consequences of inadequate supplies of calcium or phosphorus. Phosphorus can be supplied on a digestible basis with reference to tables of nutritive values of feedstuffs, but this is presently not the case for calcium. Consequently, different hypotheses for calcium digestibility are used in the model, which will need to be updated (as well as the definition of the maintenance requirement). Given these limitations, the model is used to investigate the effect of physiological stage and productivity level (prolificacy, milk production) on the daily requirement of calcium.; Le coût élevé des sources de phosphore et l’impact d’un apport en excès de cet élément sur l’environnement conduisent à restreindre les apports en phosphore aux besoins chez la truie reproductrice. Au contraire, les sources de calcium sont peu onéreuses et, en l’absence de contrainte de teneur maximale sur cet élément, sa teneur peut être assez élevée dans les aliments. Phosphore et calcium doivent pourtant être apportés de façon équilibrée. Un modèle est proposé pour estimer en pratique les besoins en calcium de la truie reproductrice sur la base des connaissances disponibles, beaucoup plus limitées pour cet élément que pour le phosphore. Le modèle ne peut pas être utilisé pour simuler les effets d’une carence en l’apport de l’un ou l’autre minéral en raison des difficultés d’évaluation du degré de minéralisation osseuse qui conduisent à ne pas prendre en compte ce critère. Les tables de valeurs nutritionnelles des matières premières permettent de raisonner l’apport en phosphore sur une base digestible, mais ce n’est pas encore le cas pour le calcium. Une hypothèse de digestibilité est donc appliquée dans le modèle pour estimer le besoin en calcium total, qui devra être actualisée (de même que le calcul du besoin d’entretien) dès que les tables de valeurs des matières premières permettront de formuler les aliments sur la base du calcium digestible. Ces réserves étant posées, le modèle est utilisé pour quantifier le besoin en calcium selon le stade physiologique de la truie et son niveau de production (prolificité, production de lait).

International audience; Growth performance of pigs obtained with three feeding strategies were compared. Strategies ALA, ALB and RAA differed by the feeding level (AL: ad libitum, RA: restricted) and the 3-phase feeding sequence that met amino acid requirements or not (subscripts A and B, respectively). Two batches (b1 and b2), each with 4 pens of 6 gilts or barrows per treatment, were used. Batch 1 was studied in winter and b2 in summer with the outdoor temperature being onaverage 10 °C higher so that it was not possible to keep the indoor condition at the thermoneutral level and the daily feed intake (DFI) of ALA decreased by 20% (ALA/b1: 2.12 vs ALA/b2: 2.49 kg/d, P0.05, ALB/b1: 2.42 vs ALA/b1: 2.38 and ALB/b2: 2.13 vs ALA/b2: 2.00 kg/d) but decreased ADG, resulting in a higher FCR (P0.01) on average in both batches, with a larger difference in gilts, especially under warm conditions (b2). This study demonstrated that both FCR and carcass leanness were improved by a more adequate AA nutrition but that only carcass leanness was improved by feed restriction. It may be due to a different partition of energy intake between different functions (growth vs activity) and could motivate a more precise grading of the entire carcass to assess more accurately consequences of feeding strategy and ambient conditions on the composition of BW gain and final carcass value.

The dynamic model ThermiPig was developed to simulate thermal balance at the fattening room scale, as the result of the balance between the heat produced by the group of pigs or provided by incoming air and equipment and that lost due to air renewal or thermal conductivity of the walls and ceiling. A growth model (assuming thermoneutral conditions, InraPorc) and a bioclimatic model (ThermiSim) were combined to create ThermiPig; it considers a common time step (1 hour), definition of the pig thermoneutral zone, evaluation of impacts of cold and hot exposure on the amount of available energy for growth, and the circadian distribution of heat produced daily by each pig. Data collected in vivo were used to evaluate the accuracy of the prediction of ambient temperature, which averaged 0.6°C (RMSEP, error of prediction). ThermiPig was used to simulate impacts of alternative regulations for ventilation or the use of new equipment (heater, pad cooling) on growth performance of pigs, N excretion, and indirect energy (from feed intake) and direct energy (from electricity consumed by equipment) consumption. Comparison of multi-criteria performance in silico helps identify the most interesting option. Economic performance depends on carcass value (based on the French payment grid) minus costs of feed intake and electricity (depending on the energy source). However, more accurate prediction of carcass value is expected in the next version of the model by considering effects of ambient temperature on the distribution of body fat and protein metabolism., Un modèle de croissance du porc élevé dans des conditions de thermoneutralité (InraPorc) est combiné à un modèle permettant de simuler l’équilibre thermique de la salle d’engraissement selon la chaleur apportée par l’air entrant, les équipements ou les animaux, et les déperditions par la ventilation ou les parois (ThermiSim). La jonction de ces deux modèles repose sur le choix d’un pas de temps commun (1 heure), la définition de la zone de confort thermique pendant l’engraissement, la quantification des effets de l’exposition au chaud ou au froid sur la quantité d’énergie disponible pour la croissance, et enfin la répartition dynamique de la chaleur produite par les animaux au cours de la journée. Les résultats d’un essai in vivo sont utilisés pour évaluer la précision de prédiction de la température ambiante par ce modèle, appelé ThermiPig ; elle est en moyenne de 0,6°C (RMSEP, erreur de la prédiction). Des simulations sont ensuite réalisées pour évaluer l’incidence d’un changement des règles de régulation du boîtier de ventilation et de l’installation de nouveaux équipements (chauffage ou pad cooling) sur les performances de croissance du groupe de porcs, leurs rejets azotés, leur consommation d’énergie directe (électrique) et indirecte (aliment). En comparant les résultats des simulations, il est possible d’identifier la situation la plus intéressante sur la base de ces différents critères. La différence entre lavalorisation des carcasses dans la grille de paiement et le coût alimentaire et en électricité pour faire fonctionner les équipements, qui dépend de la source d’énergie utilisée pour produire l’électricité, permet d’évaluer la performance économique. Toutefois, la prédiction de ce critère doit encore être affinée par une prise en compte plus précise de l’influence de la température sur la conformation des porcs et sur leur métabolisme protéique.

International audience; Purpose. Feed production and excretion of nutrients by the animals are major sources of the environmental impacts of pig production. New communication and information technologies (NTIC) allow the development of precision feeding (PF) in pig-fattening units, which appears as a promising way to decrease environmental impacts of pig production. Therefore, we performed a life cycle assessment (LCA) of pig production with either conventional or PF applied to growing-finishing pigs.Methods. Two sources of data were involved: experiments and simulations performed using a model of pig fattening. A first experiment compared two-phase (2P) ad libitum (AdLib) feeding to ad libitum PF. A second experiment compared 2P restricted (Res) feeding to restricted PF. With the model, four feeding programs – 2P, 2PLCP (2P with low crude protein content), MP (daily multiphase group feeding) and PF – were simulated according to two feeding levels: AdLib and Res. A cradle-to-farm gate LCA was performed for each strategy, with the kg of live pig at farm gate being the functional unit. Five categories of impacts were evaluated: ILCD climate change (CC), ILCD acidification (AC), CML 2001 eutrophication (EU), CML 2001 land occupation (LO) and CED V1.8 non-renewable and fossil energy demand (CED).Results and discussion. PF slightly increased feed conversion ratio (FCR) and total feed intake compared with their reference 2P strategies, excepted in the in vivo experiment comparing PF-AdLib to 2P-AdLib. In this latter case, FCR was improved with PF. PF resulted in reduced N intake and N excreted relatively to 2P feeding in both in vivo and virtual experiments, whatever the rationing plan applied. PF always decreased AC and EU by reducing nitrogen excretion. With experimental data, CC was reduced in PFAdLib but not in PFRes compared to their respective 2P strategies. Simulated results showed a decrease in AC, EU and LO impacts, but not in CC, what is probably due to the small difference in total feed consumption between ad libitum and restrictedly-fed pigs (5 kg/pig). Conclusions. PF can reduce environmental impacts of pig production, particularly AC, EU and LO. Nevertheless, the definition of constraints on amino-acid and crude-protein contents and feed formulation should be made in accordance with local practices (i.e., feeding level) in order to obtain environmental gains expected with PF.

International audience; A test was performed with 96 growing pigs to implement precision feeding (PF) of restricted-fed growing pigs to characterise growth performance and N output using a PF system developed in the Feed-a-Gene project (H2020, no. 633531) compared to a 2-phase strategy (2P). A decision support tool was used to manage data (mainly individual and daily body weight (BW) measured with an automatic scale), to forecast performance on the following day, to assess corresponding amino acid requirements, and to adapt the quality of the diet delivered on the next day through the proportion of two diets used in a blend. Both diets were formulated to 9.75 MJ net energy (NE)/kg, with contrasting concentrations of digestible lysine and crude protein (A: 1.0 g lysine/MJ NE and 16.6% N x 6.25, B: 0.5 g/MJ NE and 10.9% N x 6.25). Forecasting BW and BW gain for PF pigs was interrupted for 2 weeks due to a problem with an electronic device for 2 consecutive days; it identified a problem of robustness in how forecasting methods were applied. A solution was found and applied to improve the entire system. However, no significant differences were observed between strategies for growth rate (2P: 722 vs PF: 716 g/d, P = 0.62), feed conversion ratio (2.64 vs 2.70, P = 0.063) or carcass leanness (62.0 vs 61.4 units, P = 0.18). The crude protein content of the blend provided to 2P during the growing and finishing phases was 15.8% and 13.4%, respectively. With this new 2P diet management, N output can potentially be reduced by 10% compared to a 2P with standard diets (16.0% and 15.0% N x 6.25). Despite the technical problem, which might have minimised the difference in N intake betweenstrategies, the PF contributed an additional decrease of 6%.

International audience; Precision feeding (PF) in growing-finishing pigs appears as a promising technology to decrease environmental impacts of pig production. However, few studies have compared environmental impacts of conventional and PF. Therefore, the aim of this study was to perform life cycle assessment (LCA) of pig production with either conventional or PF applied to growing-finishing pigs. Two approaches were used: using data from two experiments or relying on simulations performed with a fattening-unit model. In the ExpAdLib experiment, two-phase ad libitum (AdLib) feeding was compared to ad libitum PF. In the ExpRat experiment, two-phase restricted (Res) feeding was compared to restricted PF. In the model, four feeding programs − S2PREF (reference two-phase), S2LowProt (two-phase with low protein content), SMPGr (daily multiphase group feeding) and SMPInd (daily multiphase individual feeding) − were simulated according to two levels of supply: AdLib and Res. PF always decreased acidification and eutrophication impacts by reducing nitrogen excretion. Experimental results showed that climate change was reduced in PF AdLib but not in PF Res. Simulated results showed decrease in acidification, eutrophication and land occupation impacts, but not of climate change because of a worse feed conversion ratio. This LCA confirms that PF is a technology for reducing environmental impacts of pig production, particularly acidification and eutrophication. Nevertheless, definition of constraints on amino-acid and crude-protein contents, feed formulation and definition of the level of feed restriction should be made carefully in order to obtain the expected environmental gains with PF.; L’alimentation de précision (AP) des porcs charcutiers pourrait réduire les impacts environnementaux de la production porcine. Pourtant peu de résultats ont été publiés sur ce sujet. Cette étude visait à évaluer par analyse du cycle de vie les impacts de l’AP de porcs charcutiers en comparaison d’une alimentation conventionnelle. Deux approches sont utilisées : l’une reposant sur des données obtenues dans deux expérimentations et l'autre sur des simulations réalisées avec un modèle de l’atelier d’engraissement. Dans l’expérimentation ExpAdLib, une stratégie biphase (2P) ad libitum (AdLib) a été comparée à une AP AdLib. Dans l’expérimentation ExpRat, une stratégie en biphase rationné (2Prat) a été comparée à une alimentation de précision rationnée (Rat). Quatre programmes d’alimentation ont été simulés : S2PREF = biphase deréférence, S2PBasProt = biphase à basse teneur en protéines, SMPGr = multiphase journalier groupe et SMPInd = multiphase journalier individuel, selon deux plans de rationnement : AdLib et Rat. L’AP réduit de façon systématique les impacts acidification et eutrophisation, grâce à la réduction de l’excrétion d’azote. Pour l’impact sur le changement climatique, les résultats expérimentaux suggèrent une amélioration en AP AdLib mais pas en AP Rat. Les résultats simulés font état d’une amélioration claire sur l’acidification, l’eutrophisation et l’occupation des sols, mais pas d’amélioration sur le changement climatique en raison de la légère augmentation de l’indice de consommation. Cette étude confirme que l’AP est un levier de réduction des impacts environnementaux de la production de porcs charcutiers, particulièrement pour l’acidification et l’eutrophisation. L’AP doit faire l’objet d’une approche globale incluant la définition des niveaux d’acides aminés des aliments, la formulation des aliments, et la définition du niveau de rationnement, pour obtenir le meilleur gain environnemental.

International audience; Within the Horizon 2020 EU program Feed-a-Gene, a decision support system (DSS) was developed to implement precision feeding (PF) in commercial pig farms and to help improve feed efficiency. This study aimed to perform PF with the DSS in practical conditions with growing pigs fed ad libitum and to assess consequences on performance and nutrient use. Sixty-four pigs were reared from 77 to 161 days of age (33.5 to 108.8. kg body weight, BW) in a single pen equipped with an automatic weighing-sorting system and eight automatic feeders that register feed intake and deliver a tailored blend of two diets (A and B, respectively 1.0 and 0.4 g SID Lysine(Lys)/MJ net energy (NE), and 9.7 MJ NE/kg) to individual pigs. The control group received a blend providing 0.9 g Lys/MJ NE until the group weighed 65 kg on average (growing phase) and 0.7 g Lys/MJ NE thereafter (finishing phase). For the PF group, the Lys requirement was assessed individually and on a daily basis, based on up to 20 previous records of BW and feed intake, and diets A and B were blended accordingly. Daily feed intake, average daily gain, and feed conversion ratio did not differ between treatments. During the growing period, Lys and nitrogen (N) intake and N excretion were 11%, 9%, and 14% lower in the PF group than those in the control group, respectively (P < 0.05). During the finishing period, these values were only numerically lower (difference 0.66). These results could be explained by the slightly higher feed intake in the PF group (+100 g/d, P = 0.24) and the lower Lys content used during the finishing period of the 2-phase strategy compared to standard diets.

National audience

Pig livestock farming systems encounter several economic and environmental challenges, connected with meat price decrease, sanitary norms, emissions etc. To deal with these issues, methods and models to assess the performance of a pig production system have been developed. For instance, Thermipig model represents the pig fattening room and simulates performances of pigs at the batch level, taking into account interactions between the individual variability of pigs, farmer's practices, room characteristics and outdoor climate conditions. The model requires some static basic inputs fulfilled in several spreadsheets (such as rooms, pigs, and dietary characteristics) but also data files for voluminous variable inputs (such as outdoor temperature or climate control box parameters) for further modelling and outcome producing. This leads to challenges in data providing by the farmers and have to be improved. This paper deals with the implementation of the separate modules of the developed data warehouse system for usability improvements of the Thermipig model. The idea is to substitute input from the data files with online data input and automated variable processing by the model using the python script for connection to the remote data warehouse. The data warehouse system is extended with ‘Property Sets’ section dealing with all the operations that can be performed to a set of input variables. This approach demonstrates the ability of the data warehouse to act as data supplier for the remote model. As well the outcome of the model is also transferable back to the data warehouse for evaluation. This work is done within the Era-Net SuSan PigSys project - Improving pig system performance through a whole system approach.

La plupart des porcs élevés en Europe sont logés en bâtiments dont l'ambiance est contrôlée, combinantconsommation directe et indirecte d'énergie. L'énergie indirecte dépend de l'aliment (quantité, qualité) fourni auxanimaux, du nombre de porcs et de leurs performances. Les modèles bioclimatiques représentent et prédisent labalance énergétique et la consommation directe d'énergie à l'échelle de la salle, selon les caractéristiques dubâtiment, la gestion de l'ambiance et les performances moyennes des porcs. Les modèles de croissance actuelssimulent dynamiquement les performances des porcs mais en condition de thermoneutralité. Un modèle a étédéveloppé dans le projet Pigsys (H2020 EU EraNet SusAn, convention 696231 ), combinant un modèlebioclimatique (Thermisim) et le modèle de croissance lnraPorc pour évaluer les performances des porcs encroissance et la consommation d'énergie à l'échelle de la bande de façon dynamique, selon les caractéristiques de la salle, la stratégie alimentaire, la gestion de l'ambiance et les conditions climatiques extérieures. Le modèle, écrit en langage Python, est un modèle multi-agent, mécaniste, dynamique, déterministe, individu centré. li se base sur Thermisim et sur Mogador, qui inclut une version modifiée d'lnraPorc (calcul des performances individuelles au sein d'une population), un générateur de populations et des outils gérant le taux de mortalité et la stratégie d'abattage. Les principaux développements ont consisté à définir i) un pas de temps horaire conciliant ceux de Thermisim (seconde) et Mogador (jour); ii) l'influence des conditions d'ambiance au jour J sur la consommation d'aliment au jour J+ 1; iii) la répartition circadienne de l'ingestion selon le nombre de repas; iv) l'effet des repas sur la production de chaleur des animaux; v) les limites de thermoneutralité en fonction du poids du porc. Le modèle complet a été évalué sur une base de données issues d'une bande de porcs élevés en France, comprenant le profil de croissance, les détails sur les aliments reçus, les caractéristiques de la salle et de gestion d'ambiance, et des mesures de température à l'intérieur et à l'extérieur toutes les 15 minutes.Les performances de croissance in silico sont similaires aux performances in vivo (i.e., RMSEP relative inférieure à 2,6% pour le gain moyen quotidien, la consommation alimentaire et l'indice de consommation). La température ambiante simulée diffère des valeurs mesurées de moins de 0,5°( en moyenne, ce qui est inférieur à la précision de la mesure. Etant données cette précision et la contribution majeure du taux de ventilation dans la régulation de la température, la prédiction du taux de ventilation est considérée conne suffisamment fiable. Le modèle sera maintenant utilisé pour évaluer les performances des porcs selon différentes conditions climatiques, stratégies alimentaires, caractéristiques de bâtiment ou de régulation d'ambiance.

Modelling growth performance of pigs and within-room thermal balance in different local conditions. 70. Annual Meeting of the European Federation of Animal Science (EAAP)

National audience; Precision feeding is a promising strategy to improve the efficiency of resource use by improving the adequacy between nutrient supplies and animal requirements. Technologies that identify each pig within a group (RFID ear tags), weighs it automatically and mixes different diets to adapt the quality of the feed ration on an individual and daily basis (precision feeders) were combined in a decision support system developed in the H2020 Feed-a-Gene project. It also includes a conceptual model to estimate nutritional requirements that relies on prediction of body weight (BW) and BW gain. These day D+1 criteria must be predicted from daily and individual measurements of BW performed up to day D on growing pigs group-housed in a pen equipped with an automatic weighing scale. The BW predicted with the Holt-Winters’ double exponential smoothing model (HWα, with the smoothing parameter α set at 0.6) were compared to measurements performed over at least 97 days on two groups of 96 pigs. From the 85 and 83 individual growth curves available, the slope of the regression between mean measured and predicted BW averaged 0.98 (R² = 0.99). Based on 9080 and 7662 measured BW available (respectively in each group), mean daily RMSEP regularly varies over time around 4-5% (without any particular event during the trial). Consequently, the accuracy of the prediction method was considered to meet expectations.

National audience

Improvement of feed efficiency in growing pigs is a key issue for the economic and environmental sustainability oflivestock production. This can be achieved with novel techniques such as precision feeding (PF). Within the Horizon 2020 EU Feed-a-Gene program (grant agreement n°633531), a decision support system (DSS) was developed to implement precision feeding in commercial pig farms. This study aimed to test the functioning of the DSS in practical conditions and the consequences on performance and nutrient use of growing pigs fed ad libitum. Sixty-four pigs were reared from 77 to 161 days of age (34 to 109 kg body weight, BW) in a single pen equipped with an automatic weighing-sorting system and eight automatic feeders allowing to register feed intake and deliver a tailored blend of two diets (A and B with respectively 1.0 and 0.4 g SID Lysine (Lys)/MJ NE, and 9.7 MJ NE/kg) to individual pigs. Pigs of the control group received a blend providing 0.9 g SID Lysine (Lys)/MJ NE until the average group BW was 65 kg (growing phase) and 0.7 g SID Lys/MJ NE thereafter (finishing phase). For the PF group, the assessment of the SID Lys requirement was performed individually and on a daily basis, based on up to 20 previous records of BW and feed intake. Feed composition was changed accordingly by blending diets A and B in appropriate proportions. Daily feed intake, average daily gain, and feed conversion ratio did not differ between treatments for the overall period or per period. During the growing period, the SID Lys intake and the nitrogen intake and excretion were respectively 10.8, 8.8, and 14.4% lower in the PF group compared to the control group (P0.68). This could result from a slightly higher feed intake (+100 g/d, P=0.24) in PF group combined with a SID Lys supply already low in control group. A second experiment will be performed in the same conditions to confirm the potential of the PF using the developed DSS.

International audience; Nutritionists, feed companies and equipment manufacturers look for solutions that help farmers to improve sustainability of pig production. Based on experimental results obtained in silico or in vivo, a better adequacy between amino acid supplies and requirements increases feed efficiency and farmer’s income and reduces the environmental impact of growing pigs, highlighting the interest for precision feeding. Data are collected to characterize daily animal traits (e.g. body weight, BW) and their variation from one day to another (e.g. growth rate, ΔBW). They are used to determine the requirement for maintenance and growth on the next day, respectively. Therefore, adequacy between requirements and supplies depends on these predicted BW and ΔBW. The double exponential smoothing (Holt-Winters) method with a smoothing parameter α=0.6 (HW0.6), presents a low sensitivity to the number of latest values used to forecast BW. It seems to allow for a secured prediction of BW soon after the beginning of the growing phase (at least after 4 days). A group of pigs was used in restricted feeding conditions to compare results obtained either with a 2-phase feeding strategy, considered as the control treatment, or a precision feeding strategy based on BW forecasting with the HW0.6 method. Pigs allocated to both treatments were group-housed in the same pen, equipped with the decision support system built in the Feed-a-Gene project to manage the data, to determine in real-time the corresponding nutritional requirements, and to adapt the feed characteristics provided to each pig through the blend of two diets (9.75 MJ net energy/kg, 0.5 or 1.0 g of digestible lysine per MJ). Available results from 24 pigs per treatment indicate that overall average growth performance were not influenced by the feeding strategy (P>0.58 for both average daily gain and feed conversion ratio) but digestible lysine intake was reduced by 6% (1,774 vs 1,879 g, P

Even though animals are from the same genetic line, farmers have to cope with variability both in sows and piglets. In sows, variability is observed in traits such as parity, prolificacy, appetite, body weight (BW) and back fat thickness (BF). For instance, at the beginning of gestation, variability in body condition among sows can be high due to parity and age. In addition, at a given age, variability in litter size, milk potential, and appetite results in different nutrient requirements and consequently in variability of changes in maternal body reserves. Variability in BF can be a problem as several studies have indicated that too high or too low BF values are to be avoided at farrowing as well as at weaning. In both cases, the longevity of the sow is impaired, and farmers are advised to manage the sows toward a target BF depending on the physiological stage, associated with an age-dependant BW, increasing with age up to mature BW. In addition, variation in sow’s body condition at farrowing and in prolificacy influences the new born and weaning piglet traits. Compared to less prolific sows, high-prolific sows farrow more piglets, which are both lighter on average and more heterogeneous. Compared to normal birthweight piglets, the survival rate of low birthweight piglets is lower. Providing additional care around birth helps these piglets to survive, but subsequent housing and feeding management have to be adapted to deal with the variability in their growth potential. Nutritional strategies (based on modelling approaches that take into account criteria that influence requirements) are suggested to optimise the expression of the animals’ potential, but most often without an intention to reduce inter-individual variability in growth performance. In order to control or reduce variability, other solutions have been evaluated in experimental studies that focus on the level and the dynamic of the feeding plan and the quality of the diet. The challenge is now to validate these solutions in production units, which will be more or less easy depending on the existing housing and feeding systems, and the economic, welfare and environmental context.

National audience; Two trials were carried out to compare the farrowing process and piglet characteristics (body weight, survival rate, and diarrhoea) from birth to weaning when sows (168 in total) are fed on an iso-net energy (NE) basis with a gestation (G) or a lactation (L) diet from the arrival in the farrowing unit to the day of farrowing. In both trials, NE and digestible lysine contents were fixed to 9.0 MJ and 5.0 g/kg, respectively, for the G diet and to 9.7 MJ and 8.5 g/kg for the L diet. In trial 2, diet G contained more insoluble fibre and diet L contained more soluble fibre than those of trial 1. When diet G was replaced by diet L, the daily allowance was reduced by 200 g/d (nulliparous sows: 3.0 kg L vs 3.2 kg diet G/d) or 300 g/d (other parities: 3.2 kg L vs 3.5 kg G/d) so that daily supply of NE was similar for both treatments. The iso-NE switch from diet G to L did not significantly impair frequency of faecal excretion before farrowing, sow body temperature after farrowing or frequency of diarrhoea in litters. During trial 2, diet G significantly improved the farrowing process at the beginning of parturition, whereas diet L improved it at the end. A better survival rate was observed for small piglets (i.e., weighing less than 1 kg) with diet L. The statistical power was not high enough to obtain a significant improvement in average birth weight with diet L (1.45 vs 1.41 kg, P = 0.34), but the number of small piglets tended to be smaller with diet L before farrowing. More investigation on the relationship between soluble fibre and the farrowing process or with an earlier supply of diet L would be interesting.; Le déroulement de mise bas (MB) et les caractéristiques des porcelets de la naissance au sevrage sont comparés dans deux essais impliquant 168 truies sont alimentées sur une base iso-énergie nette (EN) avec de l'aliment de gestation (G) ou de lactation (L) de l'entrée en maternité à la MB. Dans les deux essais, l'aliment G contient 9,0 MJ EN et 5,0 g de lysine digestible (LYSd) par kg, contre 9,7 MJ EN et 8,5 g LYSd /kg pour l'aliment L. Dans l’essai 2, l'aliment G contient plus de fibres insolubles et l'aliment L plus de fibres solubles que dans l'essai 1. Lors du remplacement de l'aliment G par de l'aliment L, la ration est réduite de 200 g/j (nullipares : 3,0 kg L vs 3,2 kg G/j) à 300 g/j (autres rangs : 3,2 kg L vs 3,5 kg G/j) afin d'apporter la même quantité d'EN par jour aux truies des deux lots. Le changement iso-EN d'aliment n’impacte ni la fréquence des déjections avant MB, ni la température de la truie après MB ni la fréquence des diarrhées sur la portée. Dans l'essai 2, l'apport d'aliment G améliore le rythme de naissance en début de MB, mais l’aliment L améliore la fin de la MB, ce qui contribue probablement à une meilleure survie des petits porcelets. La puissance expérimentale de l'étude est insuffisante pour démontrer une amélioration significative du poids de naissance avec l'aliment L (1,45 vs 1,41 kg, P = 0,34), néanmoins le nombre de porcelets de moins de 1 kg tend à être plus faible dans ce lot. Il serait intéressant de poursuivre cette étude par des investigations sur la relation entre fibres solubles et MB, ou en démarrant la distribution d'aliment L plus tôt.

National audience

National audience; To maintain a profitable pig delivery, some farmers delay the last marketing from the batch so that the lightest pigs reach the optimal weight before their delivery to the slaughterhouse. According to the field investigation carried out in 22 farrow-to-finish farms in Western France, different strategies were identified, such as an increased number of departures per batch or, when the rooms have to be emptied, the transfer of the last pigs to the following batches or to specific facilities. But these practices may have negative consequences, such as increased feed intake or health risk. A classification of farms was made in connection with their characteristics and carcass data (weight, lean content). In addition, a batch of 144 pigs was studied in an experimental unit, marketed in six departures with the terminal delivery performed 57 days after the first one. Growth profiles per delivery were characterized with InraPorc® software from individual body weight and feed intake measurements, and used to simulate the growth performance of the lightest pigs of the batch with different marketing strategies. These simulations show lower performance for these “end of batch” pigs, in comparison with the first pigs slaughtered. Keeping them longer at the end of finishing period can bring between 11 and 20 euros bonus per pig, depending on the animal profile (in the economic context of the first half of 2015).; Pour optimiser le paiement des carcasses, les éleveurs peuvent attendre que les porcs les plus légers d’une bande aient atteint leur poids optimal avant de les envoyer à l’abattoir. Une enquête réalisée dans 22 élevages naisseurs-engraisseurs du Grand Ouest a permis de caractériser différentes pratiques, telles que le départ échelonné des animaux ou, lorsque les salles doivent être vidées, le transfert des fins de bande vers des locaux spécifiques ou leur mélange avec les porcs des bandes suivantes. Ces pratiques s’accompagnent cependant de contreparties économiques liées à une consommation accrue d’aliment ou une augmentation du risque sanitaire. Une classification des élevages a été réalisée en lien avec les caractéristiques des ateliers et les données d’abattage disponibles (poids, taux de muscle). En parallèle, une bande de 144 porcs a été étudiée en station expérimentale, abattue en six départs étalés sur 57 jours. Le profil de croissance moyen des porcs de chaque départ a été établi à l'aide du logiciel InraPorc® à partir des mesures individuelles de poids et de consommation d’aliment, puis il a été utilisé pour simuler les performances de croissance associées aux différentes stratégies de commercialisation des derniers porcs de la bande. Ces simulations montrent que les animaux constituant les fins de lot suivent des profils moins performants que ceux des animaux abattus en premier. L’intérêt économique de prolonger leur engraissement est réel, puisqu’après 21 jours supplémentaires, le gain de marge se situe entre 11 et 20 euros par porc concerné selon le profil animal (contexte économique du premier semestre 2015).

National audience

National audience

A feeder prototype has been developed by IFIP in association with an equipment manufacturer to perform precision feeding for 96 group‐housed growing pigs, each equipped with a RFID (Radio Frequency IDentification) ear tag. It consists in five automatic feeders (AF), one weighing‐sorting station (WS), and three areas. The WS station is placed on force sensors and allows for weighing pigs individually, with a 0.1 kg accuracy, and sorting them towards (1) the AF (pigs whose daily cumulated feed intake is presently below the daily allowance), (2) a pen for specific care or departure for the slaughterhouse (after selection by the farmer), (3) the original pen for the other cases. In case 1, the pig enters an AF, both back and front doors close automatically. Its ear RFID tag is recognized by an antenna, and successive doses of feed fall into the trough. Each AF can deliver (min 30 g) and mix two diets, and is connected to a computer that calculates the daily dietary allowances per pig, based on time, body weight (BW) and feeding strategy. In this first trial, all pigs were restricted and two feeding strategies were designed (2‐ vs 9‐ phase strategy) based on the same evolution of amino acid requirements with BW for all pigs. Taking into account pigs not adapted to the system after 9 days (n = 4), accidents (n = 2), health issues (n = 5) and those which failed to consume their feed allowance on more than 4 days (n = 14), data from 71 pigs were available at the end of the fattening period.

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UMT Ingénierie des systèmes de production porcine Session : Génétique et Qualité; The effect of feeding level (AL: ad libitum or R: restricted) on the changes in tissue composition during growth was studied in 10 females and 10 castrated male pigs by feeding level. The animals were sedated and scanned in vivo with a CT-scanner at approximately 30, 50, and 70 kg body weight (BW) (scans 1, 2, and 3). After slaughter at approximately 112 kg, carcasses were also scanned (scan 4). At slaughter, the mass and volumetric proportion of fat was lower while the proportion of muscle was greater in restrictively-fed pigs than in ad libitum fed pigs. The effect of feed restriction on the proportions of fat and muscle in the body was observed from scan 2 onwards. The CT scans made it possible to quantify the effect of a feed restriction on the dynamics of muscle and fat deposition. Between scans 1 and 3, the proportion of muscle in BW gain was higher and the proportion of fat was lower in restrictively-fed pigs than in ad libitum fed pigs, the difference of fat proportion between feeding levels being no more significant between scans 3 and 4. The correlation between the proportion of muscle (% BW) measured in vivo and the CT muscle content (% carcass weight) at slaughter increased with the age at scan and this correlation was higher in ad libitum fed pigs. These correlations are lower for the restrictively fed animals due to the effect of feed restriction on the composition of BW gain.; L'effet des conditions d'alimentation (à volonté : AL ou rationnement : RA) sur l'évolution de la composition tissulaire du poids vif (PV) est étudié à partir de 10 femelles et 10 mâles castrés par lot. Les animaux sont anesthésiés puis scannés in vivo au tomographe RX vers 30, 50 et 70 kg de PV (scans 1, 2 et 3). La carcasse est également scannée après l'abattage vers 112 kg de PV (scan 4). A l’abattage, les proportions volumique et massique de gras sont réduites et les proportions de muscle plus élevées chez les porcs RA comparativement aux porcs AL. Les mesures RX permettent d'observer un effet du rationnement sur les proportions de gras et de muscle (% PV) dès le scan 2. Entre les scans 1 et 3, les porcs RA présentent une proportion de muscle dans le gain de PV plus élevée et une proportion de gras plus faible que les porcs AL, la différence entre lots n'étant plus significative pour le gras entre les scans 3 et 4. La corrélation entre la proportion de muscle (en % du PV) mesurée in vivo aux scans 1 à 3 et le taux de muscle RX (% du poids de la carcasse) à l'abattage est d’autant plus élevée que le scan in vivo est réalisé tardivement et elle est plus élevée chez les porcs alimentés à volonté. Ces corrélations sont plus faibles chez les animaux rationnés en raison de l’effet du rationnement sur la composition du gain de PV.

UMT Ingénierie des systèmes de production porcine Session : Alimentation; In a previous study where simulations were performed on a virtual population of 2000 (Large White x Landrace) x (Large White x Piétrain) pigs, it was suggested that a feed restriction could improve the homogeneity of body weight (BW) at first departure (BW1) to the slaughter house. Growth performance obtained with two feeding plans previously tested in silico was compared with results from an in vivo experiment on a batch of pigs of the same crossbreed. Pigs were housed in pens of six pigs of the same sex each (n = 168). They were offered feed ad libitum (AL) or were restricted (RA) with an increase in feed allowance of 27 g/d to a maximum allowance of 2.40 and 2.70 kg/d, for gilts and barrows, respectively. A two-phase feeding strategy was applied, with 0,9 and 0.7 g of digestible lysine per MJ of net energy (NE) in diets provided before or after 65 kg BW (9.75 MJ NE/kg), respectively. Growth was similar to that obtained by simulation. In vivo, BW1 was more homogenous with the restricted feeding plan than with the ad libitum feeding plan (P = 0.02), in association with a more homogenous feed intake per pen. Although competition for feedwas not taken into account in the simulations, in vivo and in silico BW1 coefficients of variation were very similar (AL: 8.8 vs 8.3% / RA: 6.8 vs 5.7%, respectively). This study confirms the relevance of using simulations performed in advance from a virtual population of pigs to predict the average and variability in performance in groups of growing pigs.

L'alimentation représente près de 70% des charges dans un élevage de porcs et contribue par ailleurs à l'impact environnemental de l’élevage porcin. De ces deux points de vue, il est donc crucial de valoriser au mieux l’aliment. Les connaissances sur la croissance du porc sont nombreuses et intégrées dans des modèles de prédiction des performances ou des besoins pour un individu moyen. Le changement d'échelle vers la modélisation des performances d’une population implique de caractériser sa variabilité, ce qui a été réalisé à partir de 1288 porcs issus de dix croisements. Un nouveau générateur de population virtuelle a été élaboré qui permet de disposer de populations de porcs virtuels utilisables pour simuler l'effet de la conduite alimentaire sur leurs performances de croissance et les rejets azotés. La pertinence des résultats de simulation a été vérifiée par leur proximité avec ceux obtenus lors d'un essai in vivo. Ces résultats seront intégrés dans des démarches d'alimentation de précision., Feed represents almost 70% of cost production in piggeries. Due to economic but also to environmental concerns, utilisation of dietary supplies should be optimized. Knowledge on the average growth performance and nutrient requirements of growing pigs is important and integrated in growth models. Accounting for differences among pigs within a group supposes to characterize the variability of the population of pigs, which was performed from 1288 pigs originating from ten crossbreeds, studied in an experimental station. Based on these data, a new generator of virtual pigs was proposed and used to obtain virtual populations for which the effect of feeding strategies on performance and N output were simulated. An in vivo trial confirmed the relevance of simulation results. This work allows considering future integration of a population dimension in growth models and tools.

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