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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

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

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.

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

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).

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)., 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).

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.

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Pre-weaning piglet mortality is largely attributed to the incidence of low birth weight and birth weight variation within litter. Therefore, developing strategies to increase within-litter uniformity of piglet birth weight is important. This study investigated the effects of different feeding strategies based on specific nutrient supplies in sow diet on the within-litter variation of piglet birth weight (BW0). Four batches of highly prolific crossbred Landrace × Large White sows were used. Three dietary treatments were compared: supplies of dextrose during the week before insemination (190 g/d) and of L-arginine (25.5 g/d) from d 77 of pregnancy until term (DEXA, n = 26), a dietary supplementation of L-arginine only (25.5 g/d), from d 77 of pregnancy until term (ARGI, n = 24), and no supplementation to a standard gestation diet (CTL, n = 23). Total born piglets (TB), i.e., piglets born alive (BA) and stillborn piglets, were numbered and weighed at birth and at weaning. Data were analyzed by ANOVA using the MIXED procedure in a model that included dietary treatment (ARGI, DEXA, and CTL), initial parity (1, 2 and 3, 4 and more) and backfat thickness (below or above the average value at the onset of the experiment: 15.7 mm) as the main effects and batch as random effect. The treatment did not influence (P > 0.10) the number of piglets at birth (on average 15.6 ± 3.8 and 14.2 ± 3.6 for TB and BA, respectively) or piglet BW0 (on average 1.48 ± 0.26 and 1.50 ± 0.26 kg for TB and BA, respectively). The coefficient of variation of piglet BW0 (CVBW0) was less in litters from ARGI sows than in litters from CTL sows, and intermediate in litters from DEXA sows (for TB: 21.4, 23.4, and 25.7%, P = 0.08; for BA: 20.6, 22.5, and 25.4%, P = 0.03, in the ARGI, DEXA, and CTL groups, respectively). Irrespective of diet, CVBW0 was less (P < 0.01) in litters with 16 TB piglets or less than in the largest litters (20.9 vs. 26.5%). Litter growth rate during lactation and litter size at weaning were not influenced (P > 0.10) by dietary treatments. In conclusion, supplementing gestation diet with L-arginine during the last third of pregnancy reduced within-litter variation of piglet birth weight. Combining L-arginine dietary supply with a supplementation of dextrose before insemination provided no additional benefit.

Dans les élevages porcins français, en moyenne un porcelet né vivant sur sept meurt avant le sevrage. Le poids de naissance et sa variation intra-portée sont deux facteurs déterminants de la survie post-natale des porcelets. Aussi, définir des pratiques d’élevage visant à réduire le nombre de petits porcelets ou l’hétérogénéité des portées à la naissance permettra de concilier des impératifs de compétitivité des élevages et un souci de meilleure acceptabilité sociale de la filière. L’hétérogénéité des portées se manifeste dès la fin du développement embryonnaire et s’amplifie pendant le développement foetal. De ce fait, l’hétérogénéité pourrait être réduite par des stratégies alimentaires appliquées à la truie avant l’insémination en modulant la qualité des ovocytes et des follicules, ou pendant le développement foetal en stimulant les échanges de nutriments entre la mère et les foetus. Notre étude consiste à évaluer l’effet de stratégies alimentaires portant sur deux nutriments spécifiques, le dextrose et la L-arginine, fournis à la truie à deux périodes stratégiques, respectivement avant la fécondation et pendant le dernier tiers de la gestation. Le dextrose stimulerait la sécrétion d’insuline et d’IGF-I, et ainsi la maturation folliculaire et ovocytaire. La L-arginine est un précurseur commun de l’oxyde nitrique (NO), qui stimule l’angiogénèse et la vasodilatation des vaisseaux sanguins, et des polyamines qui régulent les synthèses d’ADN et de protéines.

Session 13A. Sow nutrition to cope with increased reproductive potential; absent

Session : Alimentation; A virtual population of 2000 pigs was used to simulate the effect of feeding strategy on the average performance and variability of the population, and on N output depending on the context of feed priees. The evolution of the average digestible lysine requirement of females was used to design a biphase strategy, combined with feed restriction or ad libitum feeding. Multiphase strategies were also tested in ad libitum conditions, with lysine levels ranging from -10% to +35% around the average requirement of females (FlOO}. Performance was simulated individually using lnraPorc® up to an average (population) final body weight of 115 kg. Nitrogen excretion and economie results were calculated in five different contexts of feed priees (2005/06 to 2009/10}, with or without limitations on the dietary crude protein content. Results indicated that the lysine supply should be 30% above F100 to maximize growth. However, when multiphase strategies above F100 are used, N excretion is increased. The best economie AA supply depends on the context of feed priees and limitation on the dietary formulation. A precision feeding technique, with tailored feed supply to individual pigs, allows for an improved margin per pig and a reduced N output. With a biphase strategy, simulations indicate that feed restriction allows for a reduction in variation in final body weight, increased margin and reduced N excretion.

La mortalité des porcelets avant le sevrage est en partie liée à l’hétérogénéité du poids de naissance intra‐portée. Notre étude évalue l’effet de stratégies alimentaires portant sur le dextrose et la L‐arginine sur l’hétérogénéité de la portée à la naissance. Dans l’essai 1, trois traitements ont été comparés qui consistaient en une supplémentation de 190 g/j de dextrose pendant la semaine précédant l’insémination et de 25,5 g/j de L‐arginine du 77ème jour de gestation jusqu’à la mise bas (lot DEXA, n = 26), une supplémentation de L‐arginine en fin de gestation (lot ARGI, n = 24), ou aucune supplémentation (lot TEM, n = 23). Les traitements n’influencent ni le nombre ni le poids des porcelets nés totaux (NT) ou nés vivants (NV). Le coefficient de variation (CVPV) du poids de naissance intra‐portée est réduit dans les lots ARGI et DEXA comparativement au lot TEM (respectivement sur NT : 21,7, 23,1 et 25,9%, P = 0,06 ; sur NV : 21,0, 22,2 et 25,6%, P = 0,03). Les performances des porcelets pendant la lactation ne diffèrent pas entre traitements.Dans l’essai 2, conduit dans un autre élevage expérimental avec différents modes de logements, seuls les traitements TEM et ARGI ont été comparés. L’effet positif de l'apport de L‐arginine n’a pas été observé (CVPV de 20,7 et 21,8% respectivement pour ARGI, n = 16, et TEM, n = 13). L’impact de la supplémentation en L‐arginine sur l’hétérogénéité des portées à la naissance pourrait dépendre des élevages et de la conduite des truies., Pre‐weaning piglet mortality is partlyattributed to within‐litter variation in piglet birth weight. This study investigated the influence of different feeding strategies on within‐litter variation of piglet birth weight. Maternal diets were supplemented with dextrose and (or) L‐arginine. In trial 1, three treatments were compared: supplementations of dextrose during the week before insemination (190 g/d) and L‐arginine (25.5 g/d) from day 77 of gestation until term (DEXA, n = 26); supplementation of L‐arginine only (ARGI, n = 24); and no supplementation (TEM, n = 23). The treatments did not influence the number or body weight of total born (TB) or born alive (BA) piglets. The coefficient of variation of birth weight (CVBW) was lower in the DEXA and ARGI groups than in the TEM group (for TB: 21.7, 23.1 and 25.9%, P = 0.06; for BA: 21.0, 22.2 and 25.6%, P = 0.03, respectively). Piglet performance during lactation did not differ among groups. In trial 2 that was carried out in another experimental herd with different housing conditions,only TEM and ARGI treatments were compared. The benefit of L‐arginine supplementation during pregnancy on heterogeneity was not observed (CVBW: 20.7 and 21.8% in the ARGI group, n = 16, and the TEM group, n = 13, respectively). The influence of L‐arginine on within‐litter variation in piglet birth weight might depend on herd and (or) sow management.

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Session 30 : Free communications: pig nutrition and management; Within a population of pigs, variation in performance and nutritional requirements can be important.Nutritionists elaborate feeding strategies that maximize economic return at the batch scale while (in somecountries) accounting for N and P excretion. To evaluate the effect of feeding strategy and feed price onperformance, its variability, economic return and environmental impact, a simulation study was carried outusing both a virtual population of 2,000 gilts and barrows and the InraPorc® growth model. The 2,000 virtualanimal profiles were generated randomly from the average of five parameters that describe growth and feedintake, while using the covariance structure of parameters obtained in a preliminary study. The effects offactors such as feed restriction, number of diets used and amino acids level in each diet were simulated withdiets formulated using the least-cost principle. Five different contexts of feedstuff prices, corresponding toaverage prices recorded for five harvesting campaigns (2005/06 to 2009/10) were used. Calculations wereperformed for the 2,000 individual animals to obtain performance at the average final BW of 115 kg for thegroup. With reference to the French payment grid, carcass value was calculated using the final individualcarcass weights and lean meat contents. Economic return was calculated as the difference between carcassvalue and the costs of feed and labor. Results suggest that the variability of final BW was reduced withan increased supply of amino acids. Feed restriction had a greater impact on variability. The price of feedingredients influenced the optimum level of amino acids for economic return and corresponding N output.These calculations should be performed monthly to adapt nutrient supplies to the economic context.

Session : Alimentation; Les modèles de croissance du porc actuels n’intègrent pas la variation entre individus. Les besoins nutritionnels d’un porc "moyen" n’étant pas représentatifs de ceux du groupe, un aliment formulé selon les besoins du profil moyen d’une bande ne correspond pas aux animaux dont les besoins sont supérieurs à la moyenne. La connaissance de la variation des paramètres clés d’un modèle et de leurs liens est nécessaire à la simulation des réponses individuelles d’une bande. Le but de cette étude est de rechercher, par une analyse factorielle multiple duale, les structures de covariance liant les paramètres individuels entre eux à partir d'observations réalisées sur 1028 animaux issus de 32 groupes de porcs étudiés à la station IFIP de Romillé (35). Chaque profil individuel est déterminé par cinq paramètres, dont trois décrivent la croissance et deux l’ingéré ad libitum. Les distributions des paramètres au sein des populations sont résumées par un vecteur des moyennes et une matrice de covariance des paramètres autour de leur moyenne. Ni le vecteur moyen ni la matrice de covariance ne peuvent être généralisés à l'ensemble des groupes étudiés, ce qui indique que la structure diffère entre populations. En pratique, il est quasiment impossible de collecter en élevage les informations définissant la structure d'une population. Néanmoins, nous proposons de recueillir, pour un élevage donné, seulement les informations permettant de construire le vecteur moyen et d'appliquer ensuite une matrice de covariance générique obtenue à partir de l'échantillon des porcs étudiés afin de simuler une réponse de population la moins biaisée possible.

National audience; Different factors are known to affect milk production in sows, especially sow parity and litter size (LS). In practice, milk production can be estimated from litter growth rate and LS. This approach is generally used for the determination of nutrient requirements.But information on factors affecting litter performance is scarce. Data from about 3 500 litters from three experimental units were used to quantify the effect of LS and parity on milk production estimated from piglet growth rate. On average, milk production reached 10.7 kg/day which is higher than most published results. Total milk production increased with LS, by about 0.75 kg/day perextra piglet, whereas the amount of milk available per piglet decreased, especially when LS exceeded 12 piglets. Milk production increased from parity 1 to 2, was the highest in parity 2 to 4 and decreased thereafter. These results will contribute to a better estimation of milk production and consequently of the variability of nutrient requirement of lactating sows.

The effect of dietary NE content on feed intake and performance of pigs was investigatedusing crossbred barrows with initial and fi nal BW of approximately 35 and 110 kg, respectively. Pigs werehoused individually and allowed ad libitum access to feed. Pigs were randomly allotted to 6 wheat andsoybean meal-based diets (8.1, 8.7, 9.3, 9.9, 10.5, and 11.1 MJ NE/kg) with 16 pigs/diet. Ratios betweenstandardized ileal digestible AA and NE were similar in all diets. Over the entire experiment, increasein dietary NE concentration was associated with a decreased ADFI (3.216, 3.216, 3.122, 2.910, 2.732,and 2.684 kg/d, respectively, for diets containing 8.1 to 11.1 MJ NE/kg; linear, P < 0.01). The NE intakeincreased as dietary NE increased from 8.1 to 11.1 MJ NE/kg (26.04, 27.98, 29.03, 28.81, 28.68, and 29.77MJ/d, respectively; linear, P < 0.01, and quadratic, P= 0.06). Average daily gain increased when dietaryNE concentration increased (1.046, 1.126, 1.135, 1.177, 1.156, and 1.152 kg/d, respectively, for dietscontaining 8.1 to 11.1 MJ NE/kg; linear and quadratic, P < 0.01). The increase in dietary NE concentrationwas associated with an increase in dressing percentage (76.5, 77.0, 77.4, 78.0, 78.2, and 78.4% of BW;linear, P < 0.01) but no differences in lean percentage (58.3, 57.9, 58.0, 57.3, 58.1, and 56.4% of HCW,respectively, for diets containing 8.1 to 11.1 MJ NE/kg; P = 0.12). When dietary NE concentrationincreased from 8.1 to 11.1 MJ/kg, the G:F increased (0.326, 0.352, 0.364, 0.405, 0.425, and 0.428 kg/kg,respectively; linear, P < 0.01), but the G:F expressed using the NE system did not change (G:F, 39.97 g/MJNE; P = 0.44). When adjusted to the same dressing yield and lean percentage, the differences in adjustedADG increased among treatments, but the adjusted G:F expressed using the NE system was not infl uencedby dietary energy concentration. These results confirm the ability of individually housed pigs to adjust theirspontaneous feed intake over a very wide range of NE concentrations (8.7 to 10.5 MJ/kg). Under commercialconditions, pigs may experience less variation in ADFI than the results obtained in this experiment because ofdifferences in dietary energy concentrations. However, it seems that only a severe reduction in dietary energyconcentration will be effective in restricting energy intake of pigs that are allowed ad libitum access to feed

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