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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).

L'accroissement de l'efficacité alimentaire est un élément clé de la durabilité économique et environnementaledes systèmes de productions animales. Cet accroissement peut être réalisé par l'application de technologiesinnovantes telles que l'alimentation de précision permise par les progrès en termes de capteurs et d'automates, et aussi d'outils d'aide à la décision (OAD). Dans le cadre du programme Horizon 2020 EU Feed-a-Gene , un OAD a été développé chez le porc et la volaille pour gérer les données et appliquer des modèles nutritionnels afin de il calculer en temps réel les besoins des animaux et ii) d'ajuster la composition et les quantités d'aliment àdistribuer. Cet outil, destiné à être utilisé en élevage commercial pour des animaux nourris individuellement ou engroupe, présente une structure modulaire pour s'adapter à plusieurs dispositifs d'alimentation, d'espèces et destades de production (porc en croissance, truie en gestation ou lactation, poulet de chair, poule pondeuse). Lesmodules sont conçus pour réaliser les opérations de façon coopérative, incluant la gestion des donnéescaractérisées par des méta-données définies pour l'alimentation de précision. L'outil permet une interopérabilitédes données entre les différents équipements (mangeoires, pesons .. . ), grâce à un encodage standard. Lesmodules sont dédiés à la vérification et la correction des données pour renseigner la base de données, laprédiction des performances (poids vif, consommation), le calcul des besoins nutritionnels et l'ajustement de laration. Des méthodes spécifiques d'analyse dynamique des données ont été testées et sélectionnées par espèce selon le nombre de données disponibles, le type de données et leur fréquence d'obtention. Le calcul des besoins nutritionnels est basé sur des modèles nutritionnels spécifiques à l'espèce ou au stade de production. Un travail a en particulier été réalisé chez la truie et le poulet de chair pour affiner les modèles existants. Les modules d'analyse et de prédiction sont actuellement conçus pour des animaux élevés en conditions optimales, mais pourront être étendus à des situations perturbées (pathologies, conditions climatiques inhabituelles) par l'ajout d'autres modèles. Pour le porc en croissance, I'OAD a été associé à des alimentateurs de précision en alimentation ad libitum ou rationnée pour des tests en élevage expérimental, avec une réduction observée de l'excrétion azotée de 7 à 10 o/o par rapport à une alimentation classique bi phase, sans modification des performances techniques. L'application de I'OAD chez le poulet de chair a permis une réduction du coût alimentaire (-5 %) et des rejets de phosphore (-6 %) malgré un indice de consommation légèrement supérieur (+0,03 point). Ces travaux montrent l'intérêt de ces OAD développés pour l'application de l'alimentation de précision afin d'améliorer simultanément la durabilité économique et environnementale des élevages de monogastriques.

La présence d’odeurs indésirables dans la viande de porcs mâles entiers est principalement liée à l’accumulation d’androsténone et de scatol. L’androsténone est synthétisée par les testicules et le scatol par les bactéries du colon à partir du tryptophane. Leur teneur dans le tissu adipeux résulte du bilan entre leur synthèse, leur élimination et leur réabsorption. Le principal levier d’action pour réduire la teneur en androsténone est la sélection génétique. Pour le scatol, les principaux leviers d’action concernent la conduite d’élevage : propreté des cases, gestion de l’environnement microclimatique et conduite alimentaire, notamment. La mixité des groupes et l’instabilité sociale ont peu d’impact sur les teneurs en composés odorants, mais sont importantes à contrôler pour réduire les risques de bagarres et de lésion. Même en réduisant fortement la teneur en composés odorants, il ne sera pas possible d’obtenir des niveaux indétectables sur toutes les carcasses. Une stratégie d’utilisation des carcasses odorantes de porcs mâles entiers doit être définie. Elle implique de comprendre les facteurs de rejet des viandes odorantes par les consommateurs. La perception d’odeurs sexuelles dépend de facteurs liés à l’animal, au type de produit, au mode de préparation/consommation et au consommateur lui-même. De plus, les deux molécules odorantes semblent interagir. La prise en compte des différents cas de figure peut être envisagée par une approche de modélisation, avec en préalable la mise en œuvre d’une détection des odeurs sur la chaine d’abattage. Or actuellement, seule la détection par le nez humain est opérationnelle au niveau des chaines d’abattage et des méthodes instrumentales restent à développer., Boar taint in pork comes mainly from the presence of two molecules: androstenone and skatole. Androstenone is produced by the testes and skatole is synthetized from tryptophan by bacteria in the colon. Their content in fat tissues results from the balance between synthesis, elimination and reabsorption. The main way to decrease the androstenone concentration is genetic selection. Regarding skatole, the main ways involve husbandry, cleanliness of pens, management of microclimatic conditions and feeding strategy. Gender mixing and social instability have little influence on boar taint but it is important to control them to decrease the risk of fighting and lesions. Even if it is possible to drastically decrease the boar taint level, it will not be possible to reach undetectable levels in every single carcass. It is necessary to define an entire male pig carcass-use strategy. It involves understanding the factors leading to consumers’ rejection of tainted pork. The perception of sexual odors depends on factors related to the animal, the type of pork product, the way of cooking/consumption and the consumer oneself. Moreover, the two odorant molecules seem to interact. A modelling approach is necessary to consider the different specific cases, which requires methods to detect the odors on-line. Currently, only the detection by the human nose is operational in slaughterhouses and instrumental methods still have to be developed.

Precision feeding is a promising way to improve feed efficiency and thus economic and environmental sustainability of livestock production. A decision support system (DSS) was built to determine in real-time the nutritional requirements of animals and feed characteristics (i.e. composition, amount) for an application of precision feeding in pig and poultry commercial farms. This tool, dedicated to animals managed individually or in groups, is designed with a modular structure for adaptation to different feeder devices, species and production stages. The modules are built to perform specialized tasks in a cooperative way. It includes a data management module with a proper characterization of data by meta-data definition for precision feeding. It ensures standard encoding to allow data interoperability from any platform. Other modules are dedicated to data verificatrion and correction for inclusion in a database, prediction of most probable body weight (BW) gain and feed intake (ad libitum or restricting feeding), and the calculation of nutritional requirements. The BW and feed intake prediction is based on dynamic data analyses. For that, specific methods have been evaluated and selected depending on the number of available data, data type (BW or feed intake), and recording frequency. The calculation of nutritional requirements is performed using nutritional models specific for a species or production stage. These two modules are currently designed for healthy animals and will be refined to extend prediction to a larger range of field situations (e.g. health problems, climatic conditions) with nutritional models in development/refinement in other workpackages of the project. The general specifications of this DSS and dynamic data analyses will be illustrated for growing pigs. This study is part of the Feed-a-Gene project and received funding from the European Union’s H2020 program under grant agreement no. 633531.

Preweaning piglet mortality is largely attributed to the incidence of low birth weight and birth weight variation within the 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 (CV(BW0)) 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, CV(BW0) was less (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.

In most countries, male pigs are physically castrated soon after birth to reduce the risk of boar taint and to avoid behaviours such as fighting and mounting. However, entire male pigs are more feed efficient and deposit less fat than barrows. In addition, many animal welfare organizations are lobbying for a cessation of castration, with a likelihood that this could lead to inferior pork unless an alternative method is used to control boar taint. An alternative to physical castration is immunization against gonadotrophin releasing factor (GnRF) which allows producers to capitalize on the superior feed efficiency and carcass characteristics of boars without the risk of boar taint. From a physiological perspective, immunized pigs are entire males until shortly after the second dose, typically given 4 to 6 weeks before slaughter. Following full immunization, there is a temporary suppression of testicular function and a hormonal status that resembles that of a barrow. Nutrient requirements will be different in these two phases, before and after full immunization. Given that there have been few published studies comparing the lysine requirements of entire males and barrows in contemporary genotypes, it is useful to use gilt requirements as a benchmark. A series of meta-analyses comparing anti-GnRF immunized boars and physical castrates and use of nutritional models suggest that the lysine requirement of entire males before the second immunization is 5% higher than for gilts, from 25 to 50 kg BW, and by 8% from 50 to 95 kg. Given that the penalty in growth performance for having inadequate dietary lysine is greater in males than in gilts or barrows, it is important to ensure that lysine requirements are met to obtain the maximum benefits of entire male production during this phase. After the second immunization, the lysine requirement of immunized males decreases and may become more like that of barrows. In addition, a consistent effect of full immunization is a marked increase in voluntary feed intake from about 10 days after the second dose. Putting these together, the estimated lysine requirement, expressed in terms of diet composition, falls to 94% of the gilt level. Although general principles can be described now, further research is needed to fully define the lysine requirements of immunized boars. It is important that the temporal pattern of tissue deposition rates and feed intake be explored to be incorporated into models to predict nutrient requirements over the period of rapidly changing metabolism.

Article disponible en ligne; Pig breeders can cope with variation in sow prolificacy as long as the total number of piglets born alive does not exceed the total number of functional teats of the sows in the farrowing unit. Cross-fostering allows adjusting the size of the litter to the milk production potential of the sow. When prolificacy increases, this objective becomes more difficult to achieve. In addition, the within-litter variation of birth weight increases with prolificacy, compromising the survival chance of small piglets. Short-term solutions can be obtained by providing additional care around birth, by grouping of pigs of similar body weight and by providing appropriate feeding strategies. Nevertheless, variability is still observed at the end of the fattening period. This results in difficulties to find the best slaughtering strategy, especially when the economic return depends on a payment grid that is based partly on carcass weight. Although genetic selection may eventually reduce the variation in performance in sows and piglets, feeding strategies that account for the individual requirement of the gestating sow can already be used to improve the farrowing process. Although this helps to improve piglet vitality at birth, to date, it is not effective in reducing within-litter variation in birth weight. Most of these improvements have been reported for sows and piglets kept in experimental facilities. It remains a challenge to obtain these results in production units.; La variabilité de la prolificité est maîtrisable par l'éleveur tant que le nombre de porcelets nés vivants n'excède pas le nombre de tétines fonctionnelles dans la maternité : des adoptions entre portées permettent alors d'ajuster le nombre de porcelets allaités aux capacités laitières des truies. Quand la prolificité est très élevée, la gestion des porcelets devient plus compliquée et la variabilité de leurs poids de naissance pénalise les chances de survie des individus les plus petits. S’ensuit aussi une variabilité accrue des performances de croissance. Des solutions à court terme peuvent être mises en oeuvre, en particulier l'adaptation selon le poids des animaux des soins pratiqués aux porcelets à la naissance, la constitution de lots de porcs sur la base du poids au sevrage et à l'entrée en engraissement, et l'adaptation des transitions alimentaires en fonction du poids moyen de chaque lot. Malgré ces pratiques, la variabilité des poids au sein d'une bande persiste jusqu’en fin d'engraissement, compliquant l'organisation des départs pour l'abattoir. Ceux-ci sont généralement gérés au mieux de l'intérêt économique de l'éleveur en relation avec la grille de paiement basée en partie sur le poids de carcasse. Sans attendre les progrès de la sélection génétique pour limiter la variabilité des performances des truies et des porcelets, la prise en compte précoce des besoins individuels des truies au sein d'une bande permettrait de gérer l'évolution de l'adiposité maternelle pendant la gestation et faciliter le déroulement des mises bas. La prise en compte de l'évolution des besoins nutritionnels au cours de la gestation par des plans d'alimentation adaptés améliore la vitalité des nouveau-nés, mais jusque-là ne joue pas sur la variabilité des poids intra-portée. Ces améliorations sont obtenues le plus souvent dans des troupeaux expérimentaux, et restent à généraliser dans les élevages de production.

A feeder prototype has been developed by IFIP and an equipment manufacturer toperform precision feeding for 96 group-housed growing pigs each equipped witha RFID ear tag. A sorting station, placed on force sensors, allows for weighingpigs individually and orienting them towards (i) five automatic feeders (AF), aslong as daily feed allowance is not reached, (ii) a pen for specific care, or (iii)the life area otherwise. Each AF can deliver (min. 30 g) and mix two diets, andis connected to a computer that calculates the daily dietary allowance per pig,based on time (initial BW × 0.04 +27 g/d up to 2.4 (gilts) or 2.7 (barrows) kg/d),body weight (BW) and feeding strategy. A trial was performed to assess theproper functioning of the system and to compare two feeding strategies (2- vs9-phase strategy, called 2P and 9P) with different amino acid supplies dependingon the BW range. Four pigs did not adapt to the system after 7 days. Sevenpigs were removed because of accidents or health issues. Eleven pigs did notconsume their feed allowance on more than 4 non successive days. During thefirst week, it was due to the high occupation rate of AF. Growth performances of74 other pigs were characterized. Average daily gain (2P: 787, 9P: 774 g/d), feedconversion ratio (2P: 2.70, 9P: 2.74) and carcass leanness (2P: 65.2, 9P: 65.1%muscle) were similar for both strategies (P > 0.22), but cumulated N intake wasreduced with the strategy 9P (4.55 vs. 4.65 kg/pig, P = 0.05).

Variability in bodyweight (BW) among pigs complicates the management of feeding strategies and slaughter. Including variability among individuals in modelling approaches can help to design feeding strategies to control performance level, but also its variability. The InraPorc model was used to perform simulations on 10 batches of 84 crossbred pigs each to characterise the effect of feeding strategies differing in amino acid supply or feed allowance on the mean and variation in growth rate. Results suggested that a feed restriction reduces the coefficient of variation of BW at first departure for slaughter (BW1) by 34%. Growth performance obtained from an in silico simulation using ad libitum and restricted feeding plans was compared with results obtained in an in vivo experiment on a batch of 168 pigs. Pigs were offered feed ad libitum or were restricted (increase in feed allowance by 27 g/day up to a maximum of 2.4 and 2.7 kg/day 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, respectively. Actual growth was similar to that obtained by simulation. Coefficient of variation of BW1 was similar in vivo and in silico for the ad libitum feeding strategy but was underestimated by 1 percentage point in silico for the restriction strategy. This study confirms the relevance of using simulations performed to predict the level and variability in performance of group housed pigs.

Forty-two multiparous Large White sows were used to investigate the effect of diurnally fluctuating temperature (T) on lactation performance and feeding behaviour. The animals were allocated to one of the four thermic treatments: constant T at 25°C (25C) and 29°C (29C) or equal-mean diurnal cyclic T varying from 21 to 29°C (25V) and from 25 to 33°C (29V). Photoperiod was fixed to 14 h of light. The sows were given food ad libitum between the 7th and the 19th day post partům. Lactation performance was measured for all sows whereas the feeding behaviour was recorded only on 28 sows. The ad libitum food intake was comparable at 25C and 25V (6•31 kg/day) as were milk production and body reserves mobilization. In contrast, food intake at 29V was higher than at 29C (4•53 v. 3•48 kg/day) with no difference in milk production between the two treatments. The increased daily food intake at 29V resulted from higher intakes over the coolest periods of the day and especially during the dark period. Neither meal size nor daily number of meals were significantly affected by T. Feeding behaviour was mainly diurnal but with differences between treatments: 0•90 of total food intake at 29C v. 0•78 at the other three T It appears that the effects of diurnally fluctuating T on lactation performance of sows depend on the mean level of T

The feeding behaviour of eight Pietrain boars (PP/M), eight Large White boars (LW/M) and nine barrows (LW/C), and six Meishan barrows (MS/C) was studied at three different stages of growth (S1, S2, S3) corresponding to average body weights (BW) of 23, 39 and 57 kg, respectively. The PP, LW and MS breeds were considered as lean, conventional and fat types of pigs, respectively. All animals were reared individually. The light pattern was 12 hours of artificial light. The type of pig significantly affected the daily voluntary feed intake (1659, 1746, 1970 and 1622 g/d in PP/M, LW/M, LW/C and MS/C, respectively). Daily number of meals was higher in PP/M (14.4) than in LW/M and LW/C (12.2 on average) and in MS/C (7.3) whereas meal size was lower in PP/M (125 g vs. 166 g in LW pigs and 250 g in MS/C). Feed intake increased linearly with BW; the increase was lower in PP/M and MS/C (+15 g per kg of BW gain) than in LW/M (+26 g per kg) and in LW/C (+35 g per kg). With increasing age, number of meals per day decreased. Simultaneously, their size increased but the increase was more important in MS/C than in other types of pigs. The pattern of feed intake was mainly diurnal and more pronounced with the increase of BW (57 and 66% of feed intake during the day at S1 and S3, respectively). The results obtained in the present experiment clearly indicate that differences observed in composition of BW gain between types of pigs are associated with differences in VFI but also with differences in feeding behaviour.

The aim of the present paper is to investigate the effect of energy supplies on growth characteristics in pigs when protein supplies are non-limiting. An experimental program was carried out at INRA between 1992 and 1994 and involved 60 pigs from three types fed at five energy levels. The effects of energy intake on protein deposition (PD) and lean gain on one hand and on lipid deposition (LD) and fat gain on the other hand were found to be very similar, which is logical with the fact that more than 55% of PD and 80% of LD are deposited in lean and fat tissues, respectively. Our results indicate that PD increases with energy supplies according to a linear–plateau relationship, which slope ( β p ) and maximum value are influenced by genotype, sex, and stage of growth. From our results and those of literature, β p is reported to vary between 2.9 and 6.1 g per MJ digestible energy (DE) intake over the 45–100 kg body weight (BW) range. Simultaneously, LD increases linearly with energy level but neither the genotype nor the sex influence significantly the slope of the relationship (14.5 g/MJ DE between 45–100 kg BW). Differences in growth response to energy intake between types of pigs result in an important variation in BW gain and its composition associated to energy intake. Therefore, characterisation of relationships between growth components and energy intake specific to each type of pig is necessary for modelling response to energy intake.

The influence of variation of ambient temperature (T) on growth performance was studied in three successive experiments, involving each 192 crossbred gilts and barrows. The T was either kept constant or fluctuated over the day by 1.5, 3 or 4.5C around 24 or 28C. Artificial light was provided between 0700 and 1900. Growth performance were lower at 28 than at 24C whichever the range of variation of T. At the mean T of 24C, the highest average daily gain (ADG) was obtained when the diurnally variation of T was 1.5C (903 vs. 881 g/d at the other T); at the mean T of 28C, the lowest ADG was obtained when the variation of T was 3C (753 vs. 789 g/d at the other T). Feed consumption was mainly diurnal: 80% of total feed intake occurred during the day when T was kept constant at 24 or 28C, this proportion decreased when variation of T was higher than 3C (74% on average at 24 4.5 and 28 4.5C). Such a result is associated with the decrease of feed intake when T increased above 24 (or 28)C during the day. Simultaneously, feed intake increased T decreased below 24 (or 28)C, especially during the night. However this adaptation did not permit to maintain feed intake level when variation of T exceeded 1.5C around 24C. Similarly, a variation of T above 1.5C around 28C induced an additional marked reduction in growth performance.

Inclusion of variation in deterministic nutritional models for growth by repeating simulations using different sets of parameters has been performed in literature without or with only hypothetic consideration of the covariance structure among parameters. However, a description of the structure of links among parameters describing individuals is required to generate realistic sets of parameters. In this study, the mean and covariance structure of model parameters describing feed intake and growth were analyzed from 10 batches of crossbred gilts and barrows. Data were obtained from different crossbreeds, originating from Large White × Landrace sows and nine sire lines. Pigs were group-housed (12 pigs/pen) and performance testing was carried out from 70 days of age to ∼110 kg BW. Daily feed intake (DFI) was recorded using automatic feeding stations and BW was measured at least every 3 weeks. A growth model was used to characterize individual pigs based on the observed DFI and BW. In this model, a Gompertz function was used to describe protein deposition and the resulting BW gain. A gamma function (expressing DFI as multiples of maintenance) was used to express the relationship between DFI and BW. Each pig was characterized through a set of five parameters: BW70 (BW at 70 days of age), BGompertz (a precocity parameter) PDm (mean protein deposition rate) and DFI50 and DFI100 (DFI at 50 and 100 kg BW, respectively). The data set included profiles for 1288 pigs for which no eating or growth disorders were observed (e.g. because of disease). All parameters were affected by sex (except for BW70) and batch, but not by the crossbreed (except for PDm). An interaction between sex and crossbreed was observed for PDm (P < 0.01) and DFI100 (P = 0.05). Different covariance matrices were computed according to the batch, sex, crossbreed, or their combinations, and the similarity of matrices was evaluated using the Flury hierarchy. As covariance matrices were all different, the unit of covariance (subpopulation) corresponded to the combination of batch, sex and crossbreed. Two generic covariance matrices were compared afterwards, with (median matrix) or without (raw matrix) taking into account the size of subpopulations. The most accurate estimation of observed covariance was obtained with the median covariance matrix. The median covariance matrix can be used, in combination with average parameters obtained on-farm, to generate virtual populations of pigs that account for a realistic description of mean performances and their variability.

Twenty crossbred (Large Wliite × Piétrain) boars were used to investigate the effect of energy intake (0·71, 0·80, 0·90, 1·00ad libitum) and body weight (BW) on growth performance, and rates of protein (PD) and lipid (LD) deposition between 40 and 100 kg BW. Daily crude protein intake was kept constant. Total PD and LD were measured according to the comparative slaughter technique (CST) during total experiment and according to nitrogen and energy balance technique at 45, 65, 80 and 94 kg mean BW. Average daily gain increased linearly with metabolizable energy (ME) intake (+36 g/MJ ME) whereas food conversion ratio was not affected by energy level (28·0 M] ME per kg BW gain). Daily PD increased from 126 to 171 g/day, and LD from 70 to 187 glday between 0·71ad libitumandad libitumME intake. Maintenance ME requirement was constant when expressed per kg BW'60 (992 kJ/day). PD varied with ME intake above maintenance (MEp) according to a linear-plateau relationship. The slope decreased with BW (+11·5 g/MJ MEp at 65 kg BW and +9·0 g/MJ MEp at 94 kg BW). LD was linearly related to MEp (+16 g/M} MEp). The LD: PD ratio in marginal empty BW gain was constant within BW class, but increased from 1/5 to 1/9 between 65 and 94 kg BW.

For centuries, entire male pigs have been castrated to reduce the risk of boar taint. However, physical castration of pig is increasingly being questioned with regard to animal welfare considerations. Immunization against gonadotrophin releasing hormone (GnRH) provides an alternative to physical castration. Using the currently available commercial product (Improvac®; Pfizer Animal Health), a two-dose regimen of a GnRH vaccine is administered. After the second vaccination, a substantial increase in feed consumption has been reported, which may be associated with increased body fatness and decreased feed efficiency when compared with unvaccinated entire male pigs. The aim of the present study was to investigate the effect of a feed restriction on these traits and on the behaviour of 120 group-housed entire males (five pigs/pen) vaccinated against GnRH. The first vaccination was performed at 62 days of age and the second (V2) at 130 days of age. Pigs were slaughtered in two batches 4 to 5 weeks after V2. They were either offered feed ad libitum over the 22 to 114 kg BW range (AL treatment) or ad libitum up to a maximum of 2.50 (R2.50 treatment) or 2.75 kg/day per pig (R2.75 treatment). Behavioural observations and skin lesion scoring were conducted 1 week before V2, and 1 and 3 weeks after V2. At slaughter, the volumetric lean meat content was measured using an X-ray computed tomography scanner. Between V2 and slaughter, the average feed intakes for the R2.75 and R2.50 treatments were 15% and 22% lower than the average AL feed intake (3.20 kg/day), respectively. Feed restriction was associated with a reduced average daily gain after V2 (846, 932 and 1061 g/day in the R2.50, R2.75 and AL groups, P < 0.01) but had no effect on the feed conversion ratio (3.00 kg feed/kg BW gain on average, P = 0.62). No difference was observed in the lean meat content (71.8%, 70.7% and 70.4% in the R2.50, R2.75 and AL groups, P = 0.14), despite a reduced backfat thickness measured in restrictively fed pigs (12.0, 13.0 and 13.6 mm in the R2.50, R2.75 and AL groups, P < 0.01). Higher skin lesion scores were observed 3 weeks after V2 in R2.50 and R2.75 pigs than in the AL ones (scores 33.4, 27.7 and 25.5, respectively, P = 0.04). These results, combined with an unimproved feed efficiency and no marked change in carcass characteristics, suggest that immunologically castrated pigs should not be restrictively fed during the late finishing period.

Knowledge of amino acid requirements in growing pigs is required to formulate diets that optimize the feed efficiency and potentially limit the environmental impact of pig production. However, not all pigs have the same amino acid requirements, and thus the same responses to a defined nutrient supply, resulting from the variation in growth potential between pigs. The objective of this review was to discuss the tools available to assess the variation in amino acid requirements in growing pigs. We also demonstrate how the integration of variability in modelling tools is possible and allows optimizing feeding strategies. Current experimental techniques allow defining the requirement of individual animals, but the extrapolation of the results obtained is limited because few animals can be studied simultaneously. Although a sufficient number of data will be required, accounting for individual variability in pig growth models allows for a dynamic analysis of requirements of large populations. Using these models to simulate populations instead of a single average pig, feeding strategies can be defined that are adapted to the studied populations and optimize performance and economical results while reducing environmental impact. Accounting for individual variability in growth modelling is also essential to develop new technologies, such as precision feeding.; Chez le porc en croissance, la connaissance des besoins nutritionnels, notamment en acides aminés, est nécessaire pour formuler des aliments permettant d'optimiser l’efficacité alimentaire et potentiellement de réduire l’impact environnemental de cette production. Cependant, tous les animaux ne présentent pas les mêmes besoins et donc pas les mêmes réponses à des apports équivalents, ce qui résulte de la variabilité du potentiel des animaux au sein d'un groupe. Cet article présente les outils disponibles pour évaluer la variabilité individuelle des besoins en acides aminés chez le porc en croissance. Nous montrons ensuite comment il est possible d'intégrer cette variabilité aux outils de modélisation afin d'optimiser les stratégies d'alimentation. Si les techniques expérimentales actuelles permettent une détermination individuelle des besoins, la représentativité des résultats obtenus sur la variabilité des besoins est limitée par le nombre restreint d’animaux étudiés. Tout en nécessitant un nombre important de données, l’intégration de la variabilité individuelle dans les modèles mathématiques de croissance du porc offre la possibilité d’analyser la variabilité des besoins de façon dynamique et sur des populations plus grandes. En utilisant ces modèles pour simuler des populations d’animaux et non plus un individu unique, des stratégies alimentaires adaptées aux populations considérées peuvent être définies pour optimiser leurs résultats zootechniques et économiques tout en minimisant l’impact environnemental. L’apport de la modélisation et la prise en compte de la variabilité individuelle amènent également à envisager le développement de nouvelles pratiques telles que l’alimentation de précision.

Quiniou, N., Quinsac, A., Crépon, K., Evrard, J., Peyronnet, C., Bourdillon, A., Royer, E. and Etienne, M. 2012. Effects of feeding 10% rapeseed meal (Brassica napus) during gestation and lactation over three reproductive cycles on the performance of hyperprolific sows and their litters. Can. J. Anim. Sci. 92: 513–524. Largely due to increased production of biodiesel, there is a greater availability of solvent-extracted rapeseed meal (RM) in France, making it competitive for feeding pigs. Nevertheless, the long-term effects of dietary glucosinolates (GSL) when feeding RM on sow reproductive and litter performance are a persistent concern to feed manufacturers. Four batches of 24 hyperprolific sows were fed to evaluate the effects of including 0 or 10% RM [14.5 µmol GLS g−1dry matter (DM) basis] in the gestation and lactation diets over three reproductive cycles. Intake of dietary GLS remained below 5 mmol d−1over the gestation period and averaged 8 mmol d−1over the lactation period, corresponding to less than 2 µmol GLS g−1DM basis. Lactation feed intake, sow body weight and backfat, and the length of the weaning-to-estrus interval were not different (P>0.05) between treatment groups. Sows fed diets with 10% or no RM farrowed 43.6 and 43.8 piglets over three reproductive cycles, respectively (P>0.05). Piglet weight at birth or weaning, survival and litter weight gain were not affected (P>0.05) by dietary RM inclusion. Similar (P>0.10) plasma thyroxin levels of sows and piglets indicated that thyroid function was not altered by RM inclusion. In conclusion, feeding gestation and lactation diets including 10% RM to hyper prolific sows over three parities was safe and did not affect sow longevity, reproductive or litter performance.

For a sustainable pork production, emission of pollutants from pig farms has to be reduced as much as possible whilst economical results have to be maximised. To evaluate different feeding strategies in terms of economic performance and environmental impact (through nitrogen excretion), we simulated herd performance using the prediction model InraPorc. A population of 1000 virtual pigs was generated. Performance of these pigs was simulated using different feeding strategies varying in digestible lysine to NE ratio in the diet (85 to 115% of the mean population requirement) and number of diets used (i.e. a 1-phase feeding strategy, a 2-phase strategy or a continuous multiphase strategy where the lysine/NE ratio was changed daily according to requirement). Diets were formulated on a least-cost basis using two contexts of ingredient prices: September 2007 (P1) or March 2009 (P2). Simulations were ended at a mean population body weight of 112 kg. Average daily gain increased while feed-to-gain ratio and duration of growth decreased with increasing lysine content. Maximum performance was achieved for a supply between 105 and 115% of the mean population requirement for lysine/NE. Increasing the lysine/NE ratio from 85 to 100% for the 1-phase strategy and to 105% for multiphase strategies reduced total feed cost in both economic contexts. The financial return (carcass payment minus feed and labour costs) increased with increasing lysine/ NE ratio and was maximal with the multiphase strategy and a lysine/NE ratio corresponding to 110% of the mean population requirement. When using a lysine/NE ratio greater than the mean population requirement, multiphase feeding strategies reduced nitrogen excretion by 3 to 16% compared with 1-phase strategy. The relationship between financial return and nitrogen excretion depended on the feeding strategy. Using multiphase strategies allows to better match the nutrient supply to the requirement. Based on feed cost alone, it allows optimizing economic return while reducing nitrogen excretion. Apart from the interest of including the variation between animals, stochastic simulation modelling can be helpful in multiple criteria evaluation of feeding practices.

Minerals, including trace-elements, and vitamins are currently introduced into the pig diet in order to obtain suitable performances for the modern pig genotype bred in confinement. Most of the mineral and vitamin contents of cereals and usual protein compounds are characterized by their poor and variable availability. Supplemental diets are then usually needed. This paper, based on literature data, reviews the pig requirement for minerals and vitamins in order to ensure economic and profitable performance. Recent research has focused on phosphorus due to environmental considerations. The widespread use of microbial phytase has decreased the need for inorganic phosphates. Cereals are particularly deficient in calcium and sodium, consequently limestone and salt are necessary to meet the pig need for these minerals. Zinc and copper are recognized as growth promoting agents but their use at high levels is detrimental to the environment. The pig diets usually contain supplemental contents of iron, manganese, cobalt, iodine and selenium. The need for these elements in pig diets is described individually. Vitamin E and choline represent the most expensive vitamins added. Choline is then usually not incorporated into the pig fattening diet taking into account the choline contents of the raw materials, while vitamin E is included at a lower level than those which improve the meat quality. Our recent research has dealt with increased levels of vitamins added in combination, calculating higher requirement of the modern pig genotype. Fewer improvements have been obtained in this way, suggesting that recommendations proposed by INRA in 1984 are mainly justified. Minerais, inclusive elementos traços, e vitaminas são atualmente adicionados nas rações de suínos objetivando obter performance adequada para genótipos modernos criados em confinamento. A maioria do conteúdo de mineral e vitamina dos cereais e compostos protéicos é caracterizada por sua baixa e variável disponibilidade. Dietas suplementares são então geralmente necessárias. Este artigo, baseado em dados de literatura, revê a exigência do suíno para minerais e vitaminas objetivando assegurar desempenho econômico e rentável. Recente pesquisa tem focado no fósforo devido às considerações ambientais. A propagação do uso de fitase microbial reduziu a necessidade de fosfato inorgânico. Cereais são particularmente deficientes em cálcio e sódio, consequentemente calcário e sal são necessários para atender a necessidade do suíno para estes minerais. Zinco e cobre são reconhecidos como agentes promotores de crescimento, mas sua utilização em elevados níveis são prejudiciais ao meio-ambiente. As rações de suínos geralmente contêm quantidades suplementares de ferro, manganês, cobalto, iodo e selênio. A necessidade para estes elementos nas rações de suínos é descrita individualmente. A vitamina E e a colina são as vitaminas mais caras a serem adicionadas. Consequentemente, a Colina não é incorporada na ração de suínos em terminação, levando-se em conta o conteúdo das matérias-primas, enquanto que a vitamina E é incluída em nível mais baixo do que aqueles que melhoram a qualidade da carne. Nossa pesquisa recente lidou com níveis elevados de vitaminas adicionadas em misturas, calculando exigências mais elevadas dos genótipos suínos modernos. Poucos avanços foram obtidos dessa maneira, sugerindo que as recomendações proposta pelo INRA em 1984 são até hoje justificadas.

Part of these results was presented at the EAAP meeting (58th meeting of the European Association for Animal Production, Dublin, Ireland, 26 to 29 August 2007); International audience; Within-litter variation of piglet birth weight (BW0) is associated with an increased piglet mortality and a high variability in pig weight at weaning and weight or age at slaughter Data collected in tW0 experimental herds were used to quantify within-litter variability in BW0 and to assess the influence of factors mainly related to the sow Within 24h after birth, piglets born alive were individually weighed and stillborn piglets were collectively (first data set) or individually (second data set) weighed. The first data set was restricted to litters with no or only one stillborn piglet (3338 litters). It was used to assess the influence of genetic selection on BW0 variation by comparing litter characteristics before (1994 to 1996) and after (2001 to 2004) the development of hyperprolific sows in this herd. The second data set included all litters (n = 1596) from sows born between 2000 and 2004. For each litter mean BW0 (mBW0) and its coefficient of variation (CV(BW0)) were calculated. Then, variance analyses were performed to test the influence of litter size, parity, year of sow birth and season at conception. Prolificacy improvement was associated with an increased CV(BW0) in litters from pure Large White (LW) and Landrace X Large White (LR X LW) crossbred sows. The CV(BW0) averaged 21% and was significantly influenced by litter size and parity. It increased from 15% to 24% when litter size varied from less than 10 piglets to more than 15 piglets. The proportion of small piglets (i.e. weighing less than 1 kg) increased concomitantly. The CV(BW0) was not repeatable from a parity to the following. It was lowest for first and second parities (20%) and thereafter increased progressively. The CV(BW0) was positively related to sow's backfat thickness gain during gestation. Taking into account litter size, parity, year of sow birth and season at conception explained 20% of BW0 variation. Thus, major part of heterogeneity is due to other factors, presumably including embryo genotype, on the one hand, and factors that influence embryo and foetus development, such as epigenetic factors, on the other hand.

International audience; Two trials were carried out to compare the effects of fat or starch inclusion in sow's diet on sow and litter performance. In each trial, sows were assigned to one of two treatments. In trial 1, the sows were fed diets containing either soybean oil (5%, treatment GL5) or cornstarch (11.3%, GL0) from day 35 of gestation to weaning. Daily net energy and nutrient allowance were equalised during gestation. In trial 2 the same treatments were applied only after farrowing (treatments L5 and L0, respectively). Within each trial, a batch of piglets was studied until slaughter In trial 1, adipose cell development and total lipid content were determined on some pigs at weaning (n = 6/treatment) and at slaughter in dorsal subcutaneous adipose tissue (n = 13/group at least) and in muscle (n = 46/group at least). Piglets' birth weight was not affected by treatment in trial 1, Survival rates at birth and after 24 h of life were higher in treatment GL5 (4.0% v. 7.5% stillborn piglets in GL0 treatment, P < 0.05, 8.7% v. 12.6% of piglets alive at 24 h of age died in treatment GL0, P = 0.06). Subsequently, overall survival rate until weaning was higher in treatment GL5 (81.4% v, 75.7% of total born piglets, P = 0.03), but litter size at weaning was not significantly affected (11.3). Litter growth rate before weaning was increased when a fat-enriched diet was provided during gestation and lactation (+ 140 g/day per litter; P < 0.01) and to a lower extent when provided only after farrowing (+90 g/day, P < 0.05). Energy supply through fat did not decrease the mobilisation of the sow's body reserve and backfat thickness loss was even higher with treatment GL5 (P < 0.05). After weaning, pigs' average daily gain, feed: gain ratio and carcass lean content were not affected by the energy source supplied before and/or after farrowing. At weaning, the number of adipose cells in the dorsal subcutaneous adipose tissue and in the Longissimus dorsi muscle was higher in the GL5 pigs. Muscle lipid content at weaning did not differ between treatments, but it was higher at slaughter, around 110 kg, in the GL5 pigs (3.46% v. 2.58%, P < 0.001).

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National audience

A heat balance model was combined with a food intake model and a metabolism model, to form a larger model which estimates a pig’s response to heat stress. The combined model was implemented as a computer program, and used to calibrate, test and validate parts of the heat balance model. Heat transfer modes considered were convection, radiation and evaporation of water at the skin, and heating and humidification of air by breathing. Sensitivity analysis revealed a large effect of air temperature, humidity and velocity on heat loss, especially in a hot environment. It also showed that wetting of the pig’s skin is the most effective means to alleviate heat stress. The calibration procedure confirmed that characteristics related to heat tolerance in pigs must be re-evaluated, due mainly to the changes brought about by genetic improvement (such as reduced backfat thickness). The model was challenged using two different data sets. Although simulated results varied in the same way as measured data, more research is needed to determine more precisely some of the parameters. Long-term predictions were more reliable than those for short (1-day) periods.

National audience

International audience; Thirty-three multiparous Large White sows were used to determine the effect of high ambient temperature and level of dietary heat increment on their feeding behavior during lactation. Ambient temperature was maintained constant at 20 or 29 °C over 28-d lactation. The experimental diets fed during lactation were a control diet (NP; 17.6% crude protein) and two low protein diets obtained by the reduction of the CP level (LP, 14.6% CP) or both the reduction of CP and addition of 4% fat (LPF, 15.2% CP). The sows were given feed ad libitum between the 7th and the 27th day of lactation. Feeding behavior parameters were not influenced by diet composition. Between d 7 and d 27, daily feed intake decreased at 29 °C ($P < 0.001$; 4149 vs. 7444 g$\cdot$d$^{-1}$ at 20 °C); this was achieved by a concomitant reduction in meal frequency ($P < 0.001$; 6.5 vs. 9.4 meals$\cdot$d$^{-1}$) and in meal size ($P < 0.10$; 687 vs. 834 g per meal). The ingestion rate was not influenced by temperature (126 g$\cdot$min$^{-1}$ on average), and consequently the reduction of daily feed intake resulted in a decreased ingestion and consumption time (-25 and 28 min$\cdot$d$^{-1}$, respectively). The proportion of small meals (i.e., $

Fifty-nine multiparous Large White x Landrace sows were used to determine the effects of high ambient temperature and level of dietary heat increment on lactation and reproductive performance. During a 28-d lactation and the 14-d postweaning period, ambient temperature was maintained constant at 20 or 29 degrees C. Experimental diets fed during lactation were a control diet (NP; 17.6% crude protein) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) and both reduction of CP and addition of 4% fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP, LP, and LPF diets, respectively. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios between essential amino acids and lysine were above recommendations. During the ad libitum period (i.e., between d 7 and 27 of lactation), ADFI and NE intake decreased, respectively, from 7.63 to 4.22 kg and 82.0 to 43.3 MJ of NE when the temperature increased from 20 to 29 degrees C. Exposure to 29 degrees C reduced litter BW gain (2,152 vs 2,914 g/d) and increased lactation BW loss (34 vs 16 kg) but increased postweaning BW gain (2 vs - 4 kg). Expressed per kilogram of feed intake, water intake increased from 4.0 to 7.5 L between 20 and 29 degrees C. Compared with the NP diet, low-CP diets (LP or LPF) maintained performance and reduced total N excretion (-22.5%) in lactating sows at thermoneutrality and attenuated the negative effects of high temperature on NE intake and BW loss (40.9 vs 47.9 MJ of NE/d and 41 vs 30 kg for NP and LP + LPF diets, respectively). Temperature and diet composition did not affect the reproductive performances, and the mean weaning-to-estrus interval was 4.9 d. The respiratory rate and skin, udder, and rectal temperatures increased markedly at 29 degrees C (105 vs 33 breaths per min and 37.8 vs 36.1 degrees C, 38.9 vs 38.2 degrees C, and 39.5 vs 38.8 degrees C, respectively) without any effect of diet. In conclusion, low heat increment diets (i.e., with reduced CP/NE ratio) did not affect lactation performance of sows at thermoneutrality and attenuated the effects of high ambient temperature on energy intake and BW loss. At any ambient temperature, N excretion can be markedly reduced.

International audience; The effect of ambient temperature (T; 12 to 22 °C) and body weight (BW; 37 to 95 kg) on metabolisable energy intake (ME) and the components of energy balance was studied in six individually-housed barrows kept in a respiratory chamber. Each animal was fed ad libitum and was exposed successively in a cyclic manner to variable T (three days per T). The O$_2$ and CO$_2$ concentrations, feed intake and physical activity were continuously recorded and used to calculate total heat production (HP), heat production due to physical activity (HP$_{{\rm act}}$) and the short-term thermic effect of feed (TEF$_{{\rm st}}$). The HP and its components were modelled using non-linear equations with T, BW and ME as predictors. The results were compared to predicted values from the equations obtained in a previous experiment performed on group-housed pigs. Data indicate that adaptations of individually-housed pigs under cold exposure are more extreme when compared to group-housed animals, especially with respect to the marked increase of energy intake and physical activity. The contribution of HP$_{{\rm act}}$ to HP was on average 17 and 23% at 22 and 12 °C, respectively. Over this temperature range, the apparent efficiency of ME utilisation increased from 0.65 to 0.81. Prediction equations obtained for group-housed pigs fitted the measured HP obtained for individually-housed pigs reasonably well, which indicates that the former can be used to model energy utilisation irrespective of housing conditions (individual vs. group) when differences in feed intake under cold exposure are considered.; Effets du froid sur la production de chaleur et le bilan énergétique du porc en croissance en loge individuelle et nourri à volonté ; comparaison avec le porc élevé en groupe. Six porcs males castrés sont utilisés afin d'étudier les effets de la température ambiante (T, entre 12 et 22 °C) et du poids vif (PV, entre 37 et 95 kg) sur la quantité d'énergie métabolisable ingérée (EM, kJ$\cdot$j$^{-1}$) et la production de chaleur. Les animaux sont alimentés à volonté et exposés à des T variant de façon cyclique par pallier de 3 jours au moins par T. Ils sont logés individuellement en chambre respiratoire. Les concentrations en O$_2$ et CO$_2$, la consommation d'aliment et l'intensité de l'activité physique sont mesurées en continu et utilisées afin de calculer la production de chaleur totale (HP), celle liée à l'activité physique (HP$_{{\rm act}}$) et l'effet thermique à court terme de l'aliment (TEF$_{{\rm CT}}$). Des équations non-linéaires sont utilisées afin de prédire HP et ses composantes en fonction de T, PV et EM. Ces résultats sont ensuite comparés à ceux obtenus à partir d'équations établies chez des porcs logés en groupe. D'après nos données, l'exposition au froid entraîne une augmentation de l'EM et de l'activité physique beaucoup plus importante chez les animaux logés individuellement que chez ceux logés en groupe. La contribution de HP$_{{\rm act}}$ est de 17 et 23 % de HP, respectivement à 22 et 12 °C. Sur cette gamme de T, l'efficacité d'utilisation de l'EM augmente de 0,65 à 0,81. L'utilisation des équations obtenues chez les porcs en groupe permet de prédire avec précision l'utilisation de l'énergie chez les porcs logés individuellement quand la différence de consommation au froid est prise en compte.

The effects of ambient temperature (T; 12–29°C), body weight (BW; 30–90 kg) and metabolisable energy intake (ME) on components of energy balance were studied in seven groups of Piétrain × Large White barrows kept in a respiratory chamber. In Expt 1 (groups 1, 2 and 3), T varied in a cyclic way from 22°C to 12°C and then from 12°C to 22°C with three or four consecutive days at each of 22, 19, 16, 14 and 12°C. Similarly, in Expt 2 (groups 4, 5 and 6), T varied from 19 to 29°C and then from 29 to 19°C with three or four consecutive days at each of 19, 22, 25, 27 and 29°C. In both experiments, pigs were offered feedad libitum. In Expt 3, pigs (group 7) were exposed to the thermic conditions of Expt 1 but their feed allowance was adjusted on a BW basis to thead libitumintake recorded at 19 and 22°C in Expt 1. Groups 1, 2, 4, 5 and 7 were used over two successive cycles with initial average BW of 37 kg at cycle 1 (four pigs per group) and 63 kg at cycle 2 (three pigs per group). Groups 3 and 6 were studied at an intermediary stage of growth; their initial BW was 45 kg. The O2and CO2concentrations, physical activity and feed intake were continuously and simultaneously measured and used to calculate total heat production (HP; HPtot), HP due to physical activity (HPact), activity-free HP (HP0), and thermic effect of feed. HP was modelled as a non-linear function with T, BW and ME as predictors. Results indicate that all components of HP were proportional to BW0·60. Physical activity was minimal between 19 and 27°C (8 % ME). The estimated lower critical temperature was 24°C. Between 24 and 12°C, total thermic effect of feed decreased from 31 to 16 % ME, but the short-term thermic effect of feed (5·1 % ME) remained constant. Equations for prediction of HPtot, HPactand HP0according to BW, T and ME are proposed and evaluated according to literature values; values for the feed cost of thermoregulation in pigs are proposed.

L’exposition des porcs à des températures ambiantes élevées s’accompagne d’une chute des performances chez le porcelet sevré, le porc en croissance et la truie en lactation. Cet effet négatif de la chaleur s’exerce notamment via une diminution de la consommation spontanée d’aliment. Après avoir exposé les mécanismes impliqués dans la thermorégulation et les difficultés rencontrées pour définir la zone de confort thermique, cet article présente les effets de la température sur les caractéristiques de la prise alimentaire chez le Porc en s’appuyant sur les résultats d’un programme expérimental développé depuis 1996 à l’INRA de St-Gilles. Ainsi, il apparaît que le Porc a un comportement essentiellement diurne quelle que soit la température ambiante. Dans la gamme des températures étudiées, la moindre consommation alimentaire au chaud résulte, dans un premier temps, d’une diminution de la taille des repas alors que leur fréquence n’est pas modifiée. Cependant, d’après les résultats obtenus chez les truies allaitantes, l’accroissement de l’intensité du stress thermique provoque également une réduction du nombre de repas. Lorsque la température varie au cours de la journée autour d’une valeur moyenne de confort, le porc en croissance et la truie allaitante adaptent leur prise alimentaire aux conditions thermiques et parviennent à compenser leur moindre consommation en période chaude par une ingestion d’aliment accrue pendant les périodes fraîches de la journée. Cependant, sous des températures moyennes élevées (supérieures à la zone de thermoneutralité), la consommation alimentaire plafonne pendant les périodes fraîches et ne permet plus de compenser la chute de consommation lors des périodes chaudes., The increase of ambient temperature above the thermoneutral zone is associated with a decrease of performance in weaned piglets, growing-finishing pigs and lactating sows. This negative effect of warm exposure results mainly from a reduced voluntary feed intake. After a short presentation of the mechanisms implied in thermoregulation, the present paper will focus on the effects of high ambient temperatures on patterns of feeding in pigs. It will refer to an experimental program that began at the Pig research Station of INRA four years ago. The feeding behaviour is mainly diurnal whichever the ambient temperature and the physiological stage. Over the temperature range studied, the decreased daily feed intake with increased temperature results, first, from a meal size reduction whereas its frequency remains constant. However, data obtained in lactating sows indicate that a further increase in heat stress intensity induces a reduction in daily number of meals. When temperature fluctuates over the day around a comfort value, both growing-finishing pigs and lactating sows adapt their feed intake to environmental conditions and the lower feed intake during the warm periods of the day is compensated by an increased feed intake during the fresh periods. However under warmer temperatures (above thermoneutral zone), feed ingestion capacity does not allow for compensation of the additionnal decrease in feed intake under warm conditions and performance are reduced.

Forty multiparous Large White sows were used to investigate the effects of five ambient temperature levels (18, 22, 25, 27, and 29°C) and two dietary protein contents on their feeding behaviour during lactation. At each temperature treatment, ambient temperature was kept constant over the 21-day lactation period. Dietary protein content was either 140 or 170 g/kg with essential amino acids levels calculated to he non-limiting. Photoperiod was fixed to 14 h of artificial light. The animals were given food ad libitum between the 7th and the 19th day of lactation. Feeding behaviour was not influenced by diet composition. Over the 13 days under ad libitum feeding conditions, voluntary food intake decreased from 7·80 to 3·50 kg/day between 18 and 29°C, which was achieved through a decreased daily number of meals at the highest temperature (6·8 to 4·5 at 18 and 29°C, respectively). No significant difference among temperatures was observed on meal size, even if the highest (1372 g) and the lowest (883 g) values were obtained at 18 and 29°C, respectively. Rate of food intake was not influenced by temperature and averaged 133 g/min; consequently, decreased voluntary food intake under heat exposure resulted in reduced ingestion time (61 and 29 min/day at 18 and 29°C, respectively). Hourly food intake peaked at the beginning and the end of the light period. It resulted in a mainly diurnal partition of food intake. This partition was significantly affected by temperature as proportionately 0·87 and 0·91 of total food intake occurred during the day at 27 and 29°C, respectively, v. 0·81 on average between 18 and 25°C. Number of meals was lower during the night (1·1 v. 5·2 during the day on average); it decreased with increased temperature both during the day and the night. Meal size was lower during the night (938 v. 1080 g during the day on average). The ratio between water and food intake was significantly higher at 29°C (8·1 v. 4·2 l/kg on average between 18 and 27°C). Standing activity averaged 124 min/day with no significant difference between temperatures.

The effect of ambient temperature on individual feeding behaviour was studied in six groups of Pietrain×Large White barrows. In experiment 1 (two groups), ambient temperature varied in a cyclic way from 22 to 12°C and 12 to 22°C with three or four consecutive days at each of the following temperatures: 22, 19, 16, 14 or 12°C. Similarly, in experiment 2 (two groups), temperature varied from 19 to 29°C and 29 to 19°C with three or four consecutive days at 19, 22, 25, 27 or 29°C. In both experiments, each group was used over two successive cycles with an initial body weight (BW) of 37 kg at cycle 1 (four pigs per group) and 63 kg at cycle 2 (three pigs per group). During experiment 3, groups of four pigs were exposed to varying temperatures over one cycle either as in experiment 1 (one group) or as in experiment 2 (one group); their initial BW was 45 kg. Photoperiod was fixed to 12 h of light. In experiments 1 and 2, neither the daily number of meals (11) nor the rate of feed intake (37 g/min) were affected by temperature. The daily number of meals was lower at cycle 2 (9 vs. 12 at cycle 1 on average) but their size was higher (305 vs. 181 g/meal at cycle 1). The feeding pattern was mainly diurnal (62%). From individual data obtained at each temperature level and each stage of growth in this study ( N =296), an equation to predict the voluntary feed intake (VFI) from temperature ( T , ranging between 12 and 29°C) and body weight (BW, ranging between 30 and 90 kg) is proposed: VFI (g/d)=−1264+117 T −2.40 T 2 +73.6BW−0.26BW 2 −0.95 T ×BW (RSD=329). The present relationship indicates that VFI depends on temperature and body weight with a marked negative effect of high ambient temperatures in heavier pigs.

Multiparous Large White sows (n = 63) were used to investigate the effects of five ambient temperatures (18, 22, 25, 27, and 29 degrees C) and two dietary protein contents on their lactation performance. At each temperature treatment, ambient temperature was maintained constant over the 21-d lactation period. Dietary protein content was either 14 or 17% with essential amino acids levels calculated not to be limiting. The animals had ad libitum access to feed between the seventh and the 19th day of lactation. Diet composition did not influence lactation performance. Over the 21-d lactation, feed intake decreased from 5.67 to 3.08 kg/d between 18 and 29 degrees C. Between d 7 and 19, the corresponding values were 7.16 and 3.48 kg/d, respectively. This decrease was curvilinear; an equation to predict voluntary feed intake (VFI) from temperature (T, degrees C) and body weight (BW, kg) is proposed: VFI = -49,052 + 1,213 T - 31.5 T2 + 330 BW - .61 BW2 (residual standard deviation: 1,018). Skin temperature increased regularly with increased ambient temperature (34.6 to 37.4 degrees C between 18 and 29 degrees C), whereas udder temperature reached a plateau at 25 degrees C (38.3 degrees C). The gradient of temperature between skin and rectum was minimal (2 degrees C ) at 27 degrees C and remained constant at 29 degrees C. This constancy coincides with the marked reduction of feed intake. The respiratory rate increased from 26 to 124 breaths/min between 18 and 29 degrees C, and this indicates that the evaporative critical temperature was below 22 degrees C. The BW loss increased from 23 to 35 kg between 18 and 29 degrees C, but its estimated chemical composition remained constant. Pig growth rate was almost constant between 18 and 25 degrees C (241 g/d) and was reduced above 25 degrees C (212 and 189 g/d at 27 and 29 degrees C, respectively). In conclusion, temperatures above 25 degrees C seem to be critical for lactating sows in order to maintain their performance.

International audience

When modelling the effect of a changing nutrient supply to growing animals, it is important to distinguish the individual response curve of an animal from the change in this response that may occur during growth. A data analysis model is proposed where, for an individual animal, the relation between protein deposition (PD) and metabolizable energy (ME) intake above maintenance (MEp) is curvilinear, so that PD intersects the origin and reaches its maximum at the maximum protein deposition rate (PDmax). An increase of MEp beyond that required to attain PDmax would not change PD. The MEp not used for protein synthesis can be used for lipid deposition (LD). The relation between PD and LD on the one hand and ME on the other hand can then be described as a function of the maintenance energy requirement (MEm), PDmax, the level of ME required to attain PDmax (F; as a multiple of MEm) and the energetic efficiencies of PD (kp) and LD (kf). Of these statistics, only kp and kf were assumed to be independent of body weight (BW), age or genotype. Variation in PDmax was described as a Gompertz function (of age) whereas variation in F was assumed a linear function of BW. Maintenance energy requirement was expressed as a power function of BW. To evaluate the model, 145 nitrogen and energy (indirect calorimetry) balances were obtained from three types of pigs (Large White castrated males (cLW) and Piétrain × Large White castrated males (cPP× ) and males (bPP×)) ranging in BW between 45 and 100 kg and housed under thermoneutral conditions. Animals were allotted to one of four energy levels ranging from 0·70 to 1·00 of ad libitum intake. The MEm was not different between genotypes (849 kJ/kg BW0·60) whereas the kp and kf were 0·56 and 0·75, respectively. For castrated animals on ad libitum intake, PDmax started limiting PD at approximately 130 days of age (78 and 86 kg BW for cLW and cPP×, respectively). Before this age and for bPP×, PD was limited by MEp. In bPP×, the difference between PD and PDmax was small (less than proportionately 0·05). The F did not change with BW for bPP× (2·85 × MEm) whereas for the other genotypes, it decreased linearly from 4·47 at 45 kg to 2·00 at 100 kg of BW. Due to its nature, the model allows estimation of PDmax even when energy is restricting PD.

1 tables 1 graph. Cet article fait partie du dossier : L’augmentation de la prolificité des truies : acquis, progrès envisageables et conséquences; National audience

The effect of energy supply between 45 and 100 kg body weight (BW) on the contribution of lean tissue (muscle plus intermuscular adipose tissue) to total protein mass was studied in Large White castrated males (cLW), crossbred Piétrain × Large White castrated males (cPPx) and boars (bPPx). The pigs were allocated to four energy levels (0·70, 0·80, 0·90 or 1·00 ad libitum) and kept in metabolism cages in experiment 1 or given food ad libitum and kept in individual pens in experiment 2. Daily protein supplies were calculated to be non-limiting for growth and identical for all pigs in experiment 1. Temperature was 23°C in both experiments. The pigs were slaughtered at 100 kg BW and physically dissected; the body tissues were chemically analysed. Taking into account housing conditions, the food intake of pigs in experiment 2 corresponded to 1·20 of ad libitum intake of pigs in experiment 1; data of both experiments were combined. The energy supply and the type of pig influenced significantly the protein content of empty BW (eBW) (170 g/kg on average), of lean (184g/kg on average) and non-lean compartment (eBW minus lean, 152 g/kg on average), the proportion of total protein deposited in lean (604 g/kg of total protein, on average) but not the protein content in fat-free eBW (209 g/kg on average). The fat-free eBW can be predicted as 4·8 times the body protein mass.

The effect of energy supply on physical composition of body weight gain between 45 and 100 kg was studied in Large White castrated males (cLW), crossbred Pietrain × Large White castrated males (cPPX) and boars (bPPX). The pigs were either given food ad libitum and kept in individual pens in experiment 1, or allocated to four energy levels (0·70, 0·80, 0·90, and 1·00 ad libitum) and kept in metabolism cages in experiment 2. Daily protein supplies were calculated to be the same at the four energy levels within each type of pig and non-limiting for growth. Five additional animals for each type of pig were slaughtered at 45 kg. Daily tissue gain was measured according to the comparative slaughter technique. The daily lean gain increased with metabolizable energy (ME) intake according to a linear-plateau relationship whereas the daily fat gain increased linearly. The type of pig significantly affected the slope of the relationship between lean gain and ME intake (from 15 to 22 g per extra MJ ME) but not the slope of the relationship between fat gain and ME intake (10 g per extra MJ ME on average). Increased energy intake was associated with increased fatness of body-weight gain, which was higher in cLW and cPP× than in bPP×.

The effect of dietary crude protein level (17.7: L or 24.3%: H), on nitrogen (N) and energy utilization between 20 and 50 kg body weight, was studied in six groups of two littermate pigs fed close to their ad lib. level. Nitrogen (collection of excreta) and energy (indirect calorimetry) retentions were estimated by continuous balance; results were compared to those obtained on the same pigs by the comparative slaughter technique. Initial body composition of each group of experimental pigs was estimated from other two littermates slaughtered at the beginning of the experiment. Gaseous N, methane losses and N and energy in digesta were also measured. The L pigs retained more energy as fat (7.96 vs 4.94 MJ/d), and less energy as protein (3.19 vs 4.02 MJ/d) than H pigs. The balance technique overestimated the energy retention (+4.4%) and nitrogen retention (+2.5%) as estimated by the comparative slaughter technique. The discrepancy for N doubles when evaporation N losses were not taken into account. The higher discrepancy in energy retention measurement could be related to the accuracy in estimation of the initial body energy content, or with the underestimation of heat production by the equation of Brouwer (1965).

Growing pigs are often fed below ad libitum to increase their feed efficiency and carcass leanness. When energy supply is under control, precision feeding is implemented through the amino acids (AA). As the AA requirement depends on the body weight (BW) for the maintenance part and on its daily variation (ΔBW) for the growth part, the adequacy between requirements and supplies on day D+1 depends on the adequacy of predicted BWD+1 and ΔBWD+1. Data sets from four trials were used to forecast BW from time series analyses based either on multivariate adaptive regression splines (MARS) or double exponential smoothing (HWα) methods using the k latest data (8, 14 or 20). Pigs (n = 117) were group-housed and restrictively fed, and their BW was recorded daily and individually with an automatic scale (n = 11 736). With HW0.6, the RMSEP of BWD+1 was the smallest one (1.21 kg) and not influenced by k. Linear regression on the l latest forecasted BW was used to assess ΔBWD+1. At the beginning of the trial, ΔBWD+1 was more difficult to predict from BW forecasted with MARS than with HW0.6. Descriptive statistics of individual variation of ΔBWD+1 based on MARS and HW0.6 were comparable with k = l = 20 only after removal of the first 19 days. Compared to other methods studied, the method HW0.6 seems to be the best compromise to forecast BWD+1 and ΔBWD+1 of restrictively fed pigs.

National audience

Continuous measurements of ammonia and greenhouses gases were achieved on exhaust air from two fattening rooms differing by the type of floor (totally slatted floor vs. partially slatted floor) and the ambient temperature. Temperature was regulated at 18°C in the room with partially slatted floor (room PSF18) and 24°C in the room with fully slatted floor (FSF24). Pigs were fed ad libitum. Daily feed intake, growth rate and carcass backfat thickness were significantly higher for PSF18 pigs than for FSF24 ones, corresponding to a higher feed conversion ratio for PSF18 pigs. Under cold conditions (18°C), the N-NH3, N-N2O, C-CH4 and C-CO2 daily emissions per pig on partially slatted floor were similar to those on fully slatted floor under thermoneutral conditions (FSF24: 8.9–0.12-7.3 and 676 g, PSF18: 9.1–0.15-8.4 and 629 g/pig, respectively). A further reduction of ammonia emission from pig units on partially slatted floor would require a more pronounced reduction of ambient temperature. However, in such conditions, a deterioration of feed conversion ratio and carcass leanness may be expected. Thus, the extra-cost induced by the utilization of partially slatted floor in cold ambient conditions would not be acceptable with regard to the definition of Best Available Techniques given by the IPPC directive.