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In growing pigs, reduced growth during heat stress (HS) is mainly related to decreased feed intake. The study aimed to determine whether the reported positive effects of live yeast (LY) supplementation in HS pigs were due to a modified feeding behaviour or energy metabolism, and if these can be replicated by imposing an increased meal frequency. The effect of LY supplementation (0 (NS) v. 100 (LY) g/ton of feed), and of feeding window (FW) (unlimited or Unli, 2FW of 1 h each and 8FW of 15 min each) were measured in entire male finishing pigs (n 36). Ambient temperature was at 22°C during the thermoneutral (TN) period (5 d) and at 28°C during the HS period (5 d). Heat exposure decreased DM intake (DMI) and retained energy (RE) (–627 and −460 kJ·kg BW–0·60 · d–1, respectively; P < 0·01). During HS, LY supplementation in Unli pigs decreased inter-meal intervals (P = 0·02) attenuating HS effect on DMI which tended to improve RE (P = 0·09). NS – 8FW had higher DMI and RE than NS – 2FW (P < 0·05) but protein deposition (PD) were similar. Supplemented pigs had higher PD during HS regardless of FW (+18 g · d–1; P = 0·03). Comparing the 2FW groups, improved heat tolerance of LY-supplemented pigs were due to improved insulin sensitivity (P < 0·05) and latent heat loss capacity after a meal (P < 0·05) allowing them to increase their DMI (via an increased number of meals) and thus their energy efficiency. Imposing an increased meal frequency improved DMI in HS pigs but did not replicate positive effects of LY on PD.

In vitro models of digestion are useful tools to explore the behavior of dietary fiber sources in gastrointestinal conditions. To evaluate the validity of our digestion model, digesta obtained in vivo and in vitro were characterized and the impact of cell wall integrity on protein bioaccessibility and digestibility evaluated. Six cannulated barrows [Pietrain × (Large White × Landrace)] were included in a 2 × 2 Latin square design where they were fed two diets identical in chemical composition but differing in nutrient bioaccessibility. Pea was given either as flour (R1, most proteins encapsulated by intact cell walls) or reconstituted flour (R2, mixture of proteins and purified, broken cell walls). Digesta were collected at the duodenal and ileal cannulas at regular interval and after slaughtering, following ingestion of either R1 or R2. The two diets were also digested in vitro using a static gastrointestinal model. The original pea ingredients as well as the digesta collected in vivo and in vitro were characterized (i.e., particle size measurement, microscopy observations and gel electrophoresis) and then compared with each other. The degradation of the pea ingredients differed greatly between the two forms of flour, where particles filled with nutrients were recovered at the latest stage of R1 intestinal digestion as observed with the particle size distribution and the microscopy images. These results were consistent with the in vivo and in vitro digestibility analysis that showed lower protein hydrolysis for R1 than that for R2 (about 19% difference in protein digestion regardless of the method). Overall, great similarities were found between the digesta collected in vivo and in vitro, especially regarding the particle size measurements. To summarize, a substantial proportion of the proteins contained in R1 was retained within the pea cells following gastrointestinal digestion. These encapsulated proteins reduced the amount of amino acids and small peptides available for absorption. This mechanism will have consequences on postprandial metabolism of amino acids and bacterial population based on the delivery form of the dietary fiber.

Pigs subjected to heat stress (HS) decrease their feed intake and growth. The objectives of the experiment were to determine the effects of live yeast (LY) supplementation (Saccharomyces cerevisiae var boulardii CNCM I-1079) on feeding behaviour, energy metabolism and faecal microbiota composition of finishing boars (n 10) housed in a respiration chamber at thermoneutrality (7 d at 22°C) or during HS (seven plus six days at 28°C). Dietary LY supplementation increased DM intake (P = 0·01) whatever the ambient temperature, whereas HS decreased feed intake whatever the dietary supplementation (P = 0·01). Dietary LY supplementation increased the number of meals (P = 0·02). Energy retention was higher with dietary LY supplementation (P < 0·01) but decreased during HS (P < 0·01). The skin temperature of the supplemented pigs was lower at thermoneutrality and increased during HS to a lesser extent than that of non-supplemented pigs (P < 0·01). Faecal microbiota composition was determined using 16S rRNA gene sequencing. Treponema, Christensenellaceae R-7, Ruminococcaceae UCG-002, Rikenellaceae RC9, Clostridium sensu stricto 1 and Romboutsia genera and some bacteria belonging to Alloprevotella, Oxalobacter and Anaeroplasma genera were more abundant under HS. LY supplementation attenuated HS effects on Romboutsia abundance, while decreasing the abundance of some bacteria from Ruminoccocus, Coprococcus, Peptococcus and Oxalobacter genera and increasing the abundance of beneficial bacteria from Lactococcus and Subdoligranulum genera. Our results suggest that higher level of the keystone species Ruminococcus bromii at thermoneutrality may be one of the causes for higher energy retention observed under subsequent HS.

International audience; The study objective was to evaluate the effects of elevated temperature on carcass composition and the relative importance of each primal cut of pigs slaughtered at the same age (140 d). A sample of 48 females was reared for 60 days in two groups: one at thermoneutrality (TN, 18-24 °C) and the other in hot conditions (HS, 28-34 °C). Ad libitum access to a standard growing-finishing feed was provided. One day after the slaughter, half-carcasses were scanned by X-ray tomography to determine the tissue’s contents, and then cut according to a standard commercial procedure. Rind content was assumed to be 4% whatever the treatment. Head and feet were considered as bone. HS decreased feed intake (P

Heat stress affects pig health, welfare, and production, and thus the economic viability of the pig sector in many countries. Breeding for heat tolerance is a complex issue, increasingly important due to climate change and the development of pig production in tropical areas. Characterizing genetic determinism of heat tolerance would help building selection schemes dedicated to high performance in tropical areas. The main objective of our study was to estimate the genetic parameters for production and thermoregulation traits in two highly related growing pig populations reared in temperate (TEMP) or tropical humid (TROP) environment. Pigs came from a backcross population between Large White (LW, heat sensitive) and Creole (CR, heat tolerant) pigs. Phenotypic data were obtained on a total of 1,297 pigs using the same procedures in both environments, for body weight (BW, at weeks 11 and 23), daily feed intake (ADFI), backfat thickness (BFT, at weeks 19 and 23), cutaneous temperature (CT, at weeks 19 and 23), and rectal temperature (RT, at weeks 19, 21, and 23). Feed conversion ratio (FCR) and residual feed intake (RFI) were computed for the whole test period (11 to 23 wk). Criteria comparing the fits to the data revealed genotype × environment (G × E) interactions for most traits but not for FCR. The variance components were obtained using two different methods, a restricted maximum likelihood method and a Bayesian Markov chain Monte Carlo method, considering that traits are either similar or different in each environment. Regardless of the method, heritability estimates for production traits were moderate to high, except for FCR (lower than 0.18). Heritability estimates for RT were low to moderate, ranging from 0.04 to 0.34. The genetic correlations of each trait between environments generally differed from 1, except for FCR and ADG. For most thermoregulation traits, they also did not differ significantly from zero, suggesting that the main genetic bases of heat tolerance may vary in different environment. Within environments, the unfavorable genetic correlations between production traits and RT suggest an antagonism between the ability to maintain inner temperature and the ability to increase ADFI and ADG. However, greater RT were also associated to leaner pigs and better feed efficiency. Nevertheless, due to large inaccuracies of these estimations, larger cohorts would be needed to decide about the best breeding schemes to choose for tropical pig production.

La biodiversité, et en particulier la diversité animale, est présentée comme un levier prometteur pour la transition agroécologique et la résilience des systèmes d’élevage. Or, les travaux traitant de cette question sont peu nombreux, récents et épars. Cet article vise à développer un cadre conceptuel pour analyser de manière intégrée la diversité animale et ses modalités de gestion à l’échelle des systèmes d’élevage et à proposer des pistes de recherche pour y contribuer. Ce cadre est structuré en quatre composantes : i) les formes que recouvre la diversité animale, ii) les niveaux organisationnel et temporel auxquels elle se construit et s’exprime, iii) ses modes de gestion et iv) les bénéfices retirés par l’éleveur. Quatre études de recherche contrastées en termes de diversité animale analysée ont été revisitées au travers du cadre conceptuel proposé. Leur relecture et leur analyse transversale montrent l’intérêt d’articuler les quatre composantes du cadre pour raisonner de manière intégrée la gestion de la diversité animale en élevage afin d’en tirer parti sur le long terme. Elles permettent aussi d’identifier trois fronts de recherche à investiguer conjointement : affiner la caractérisation de la diversité animale en élevage, mieux caractériser ses modes de gestion y compris ses déterminants et approfondir l’évaluation des différents bénéfices retirés de sa gestion. Des pistes d’utilisation du cadre en recherche, en enseignement et dans conseil en élevage sont enfin proposées., Biodiversity, and particularly animal diversity chosen by farmers, is seen as a promising lever for the agroecological transition and the resilience of livestock farming systems (LFSs). However, there are few researches on it, and when available they are recent and scattered. This paper aims at developing a conceptual framework to create an integrated view of the management of animal diversity in LFSs and provide some avenues in this research topic. The framework consists of four interrelated components: the forms of animal diversity, the organizational and temporal levels at which it is built and takes place, the forms of its management in LFSs and the benefits from its management for the farmers. The framework was applied on four research studies contrasted in terms of the forms of animal diversity. The crossed case-study analysis showed that articulating the four components enables to manage in an integrated way the animal diversity in LFSs and take advantage of it in the long term. It revealed three novel research directions aiming at deepening the characterization of animal diversity, the understanding of its management in LFSs and the assessment of the various benefits derived from its management. Some avenues for using the framework in research, teaching and advice in LFS were finally suggested.

Climate change is already a reality for livestock production. In contrast to the ruminant species, little is known about the impacts and the vulnerability of pig European Union (EU) sector to climate warming. This review deals with the potential and the already measurable effects of climate change in pig production. Based on evidences published in the literature, climate change may reduce EU pig productivity by indirectly reducing the availability of crops usually used in pig feeding, spreading the vector or pathogen to new locations and increasing the risk of exposure to cereals contaminated with mycotoxins; and directly mainly by inducing heat stress and increasing the animal’s susceptibility to various diseases. Provision of realistic projections of possible impacts of future climate changes on EU pig sector is a prerequisite to evaluate its vulnerability and propose effective adaptation strategies. Simulation modelling approach is the most commonly used approach for exploring the effects of medium or long-term climate change/variability in pig production. One of the main challenges for this modelling approach is to account for both direct and indirect possible effects but also to uncertainties in parameter values that substantially increase the uncertainty estimates for model projections. The last part of the paper focus on the main issues that still need to be overcome for developing a decision support tools for simulating the direct and indirect effect of climate change in pig farms.

National audience; The objective of the study was to determine whether heat stress (HS) effects in pigs were caused directly by heat exposure (regardless of feeding level and pattern) or indirectly due to the reduction of feed intake, and to determine if splitting heat increments via increasing feeding frequency can improve pig response to HS. A total of 48 female pigs (66.1 ± 1.7 kg) were allotted to 4 groups in 3 replicates. After 7 d in thermoneutral conditions (TN; 22°C; P1), pigs were placed in either TN or HS (32°C) conditions for 20 d (P2). The diet was provided either ad libitum (AL; 2 distributions/d) or pair-fed (PF8; 8 distributions/d) using HS-AL pigs as the reference group. Thus, the 4 experimental groups were TN-AL, HS-AL, TN-PF8, and HS-PF8. Daily ration of PF8 pigs was distributed at every 90-min intervals from 09h00 to 19h30. Data was analyzed using the PROC MIXED procedure with replicate (n=3), experimental group (n=4), and their interactions as fixed effects and the REPEATED statement was used to for repeated measures data. Pigs had similar ADFI during P1 (P>0.05), while HS-AL and PF8 pigs had lower ADFI (-19%), ADG (-25%), and final BW (-6.1 kg) than TN-AL pigs (P0.05). Muscle temperature (Tmuscle) variation depended on feeding and physical activity for TN pigs while Tmuscle gradually increased throughout the day for HS pigs. Increase in Tmuscle for each meal was lower in HS-PF8 than TN-PF8 (P

International audience; With the increasing global mean temperature and more frequent summer heat waves, there is a need to find techniques to mitigate heat stress (HS) consequences on pig production. The aim of the study was to evaluate the effect of HS and of increasing feed provision frequency on performance and thermoregulation responses in finishing pigs. A total of 48 pigs (66.1±1.7 kg) were allocated to 4 experimental groups in 3 replicates. After being housed at thermoneutrality (TN; 22 °C) during 7 days (P1), pigs were subjected to either TN or HS (32 °C) conditions during 20 days (P2). In each environment, the diet (14.9%CP, 9.64 MJ NE/kg) was provided either ad libitum (AL; 2 distributions/day) or pair-fed (PF8; 8 distributions/day) with HS pigs fed-AL as the reference group. Thus, there were four experimental groups: TN-AL, HS-AL, TN-PF8, and HS-PF8. In PF8 groups, the calculated daily ration was divided into 8 feed provisions distributed at every 90-min intervals from 09:00 to 19:30. In P2, HS-AL and PF8 pigs had lower ADFI (-19% on average; P0.05). The PF8 groups had lower total viscera percentage than TN-AL pigs (-2.1% on average; P>0.05), while HS-AL had intermediate results. Pigs in HS-AL and in PF8 groups had similar slaughter BW (P

International audience; The objective of this study was to evaluate the impact of acute and repeated exposure to a diet naturally contaminated with mycotoxins (deoxynivalenol, DON) on the performance and fecal microbiota composition of finishing pigs. In total, 160 pigs raised in two successive batches were randomly distributed between four experimental groups. The control group received a standard finishing diet (uncontaminated) from 99 to 154 days of age. The experimental groups were fed a diet formulated with naturally DON-contaminated maize (3.02 mg DON/kg) for 7 days beginning on 113, 134, or both 113 and 134 days of age. Microbiota composition was analyzed using 16S rRNA sequencing applied to fecal samples collected at 99, 119, 140, and 154 days of age. DON exposure decreased daily feed intake (1.90 vs 2.64 kg/d following the first challenge period, 2.27 vs 3.27 kg/d following the second challenge period, P < 0.05). This resulted in a decrease in average daily gain measured over the entire experiment (0.94 vs 1.05 kg/d, P < 0.05). The DON challenge resulted in short-term modification of microbiota composition and bacterial functions, particularly those related to DON detoxification in the intestinal tract. After a 2-week recovery period, no difference in microbiota composition was observed between control and challenged pigs, suggesting resilience of the microbiota after perturbation caused by ingestion of a contaminated diet.; L’objectif de cette étude est d’évaluer l’impact d’expositions courtes et répétées à un aliment naturellement contaminé avec des mycotoxines et notamment de la déoxynivalénol (DON) sur les performances et la composition microbienne fécale de porcs en finition. Au total, 160 porcs issus de deux bandes successives ont été répartis aléatoirement entre quatre traitements expérimentaux. Le groupe témoin a reçu un aliment finition standard (non contaminé) entre 99 et 154 jours d’âge. Les groupes expérimentaux ont reçu un aliment formulé à partir de maïs naturellement contaminé par DON (3,02 mg DON/kg) pendant 7 jours à partir de 113, 134 et à partir à la fois de 113 et 134 jours. Une exposition à DON a entraîné une réduction de l’ingéré (1,90 vs2,64 kg/j suite à la première période d’exposition et 2,27 vs 3,27 kg/j suite à la deuxième période d’exposition, P < 0,05). Il en résulte une diminution du gain de poids mesuré sur l’ensemble de la période de test (0,94 kg/j vs 1,05 kg/j, P < 0,05). La composition du microbiote a été analysée par séquençage du gène de l’ARN 16S dans des fèces collectées à 99, 119, 140 et 154 jours d’âge. Une exposition à DON entraîne une modification temporaire de la composition microbienne et des fonctions bactériennes, notamment celles associées à la dégradation de DON dans le tube digestif. Après une période de récupération de 2 semaines, aucune différence n’est observée entre les animaux exposés et les témoins suggérant une forte résilience du microbiote suite à une perturbation liée à l’ingestion d’un aliment contaminé.

Postnatal heat stress (HS) effects on pig physiology and performance are widely studied but prenatal HS studies, albeit increasing, are still limited. The objective of this study was to evaluate the chronic prenatal HS effects in growing pigs raised in postnatal thermoneutral (TN) or in HS environment. For prenatal environment (PE), mixed-parity pregnant sows were exposed to either TN (PTN; cyclic 18 to 24 °C; n = 12) or HS (PHS; cyclic 28 to 34 °C; n = 12) conditions from day 9 to 109 of gestation. Two female offspring per sow were selected at 10 wk of age and allotted to one of two postnatal growing environments (GE): GTN (cyclic 18 to 24 °C; n = 24) and GHS (cyclic 28 to 34 °C; n = 24). From 75 to 140 d of age, GTN pigs remained in GTN conditions, while GHS pigs were in GTN conditions from 75 to 81 d of age and in GHS conditions from 82 to 140 d of age. Regardless of PE, postnatal HS increased rectal and skin temperatures (+0.30 and +1.61 °C on average, respectively; P < 0.01) and decreased ADFI (−332 g/d; P < 0.01), resulting in lower ADG and final BW (−127 g/d and −7.9 kg, respectively; P < 0.01). The GHS pigs exhibited thicker backfat (P < 0.01), lower carcass loin percentage (P < 0.01), increased plasma creatinine levels (P < 0.01), and decreased plasma glucose, nonesterified fatty acids, T3, and T4 levels (P < 0.05). Prenatal HS increased feed intake in an age-dependent manner (+10 g·kg BW–0.60·d−1 for PHS pigs in the last 2 wk of the trial; P = 0.02) but did not influence BW gain (P > 0.10). Prenatal HS decreased the plasma levels of superoxide dismutase on day 3 of GHS (trend at P = 0.08) and of T4 on day 49 (P < 0.01) but did not affect T3 on day 3 nor 49 (P > 0.10). Prenatal HS increased rectal and skin temperatures and decreased temperature gradient between rectal and skin temperatures in GTN pigs (+0.10, +0.33 and −0.22 °C, respectively; P < 0.05) but not in GHS pigs (P > 0.10). There were also PE × GE interactions found with lower BW (P = 0.06) and higher backfat (P < 0.01) and perirenal adiposity (P < 0.05) for GHS–PHS pigs than the other groups. Overall, increased body temperature and altered thyroid functions and physiological stress responses suggest decreased heat tolerance and dissipation ability of pigs submitted to a whole-gestation chronic prenatal HS. Postnatal HS decreased growth performance, increased carcass adiposity, and affected metabolic traits and thyroid functions especially in pigs previously submitted to prenatal HS.

International audience; Mycotoxins are a major contaminant of pig feed and have negative effects on health and performance. The present study investigated the impact of single or repeated acute challenges with a diet naturally contaminated with deoxynivalenol (DON) and zearalenone (ZEN) on growth performances of finishing pigs and their fecal microbiota composition. A total of 160 pigs (castrated males and females) in two successive batches were randomly divided into four experimental groups of 40 pigs each. The control group received a control finisher diet from 99 to 154 days of age. Challenged groups were subjected to a 7-day acute challenge by being fed a DON- and ZEN-contaminated diet (3.02 mg DON/kg feed and 0.76 mg ZEN/kg feed) at 113 days (group DC), 134 days (group CD) or both 113 and 134 days (group DD). Microbiota composition was analyzed via 16S rRNA sequencing from fecal samples collected from the 80 females at 99, 119, 140 and 154 days. Challenged pigs (i.e. groups DC, CD and DD) reduced their average daily feed intake by 25% and 27% ( P < 0.001) and feed efficiency by 34% and 28% ( P < 0.05) during the first and second mycotoxin exposure, respectively. Microbiota composition was affected by mycotoxin exposure ( P = 0.07 during the first exposure and P = 0.01 during the second exposure). At the family level, mycotoxin exposure significantly ( P < 0.05) decreased the relative abundances of Ruminococcaceae, Streptococcaceae and Veillonellaceae and increased that of Erysipelotrichaceae at both 119 and 140 days of age. After the 7-day DON/ZEN challenge, the relative abundance of 6 to 148 operational taxonomic units (OTUs) differed among the treatment groups. However, none of these OTUs changed in all treatment groups. Using 27 functional pathways, pigs exposed to DON/ZEN challenges could be distinguished from control pigs using sparse partial least squares discriminant analysis, with a 15% misclassification rate. Regarding the functionality of these predictors, two pathways were involved in detoxifying mycotoxins: drug metabolism and xenobiotic metabolism by cytochrome P450. In challenged pigs, microbiota composition returned to the initial state within 3 weeks after the end of a single or repeated DON/ZEN challenge, highlighting the resilience of the gut microbiome. The feeding and growth performances of the pigs during challenge periods were significantly correlated with biological pathways related to health problems and modifications in host metabolism. To conclude, short-term DON/ZEN challenges resulted in transient modifications in the composition and functions of fecal microbiota.

This study aimed to determine whether pig responses to heat stress (HS) were directly due to heat exposure (regardless of feeding level and pattern) or were indirectly due to the reduction of feed intake (FI) and to determine if increasing feeding frequency (splitting heat increments) can improve pig response to HS. A total of 48 pigs (66.1 ± 1.7 kg) were allocated to four groups in three replicates. After 7 d in thermoneutral (TN) conditions (22 °C; period 1 [P1; day −7 to −1]), pigs were placed in either TN or HS (32 °C) conditions for 20 d (period 2 [P2; day 0 to 19]). The diet was provided either ad libitum (AL; 2 distributions/d) or pair-fed (PF8; 8 distributions/d) using HS–AL pigs as the reference group. Thus, the four experimental groups were TN–AL, HS–AL, TN–PF8, and HS–PF8. The daily ration of PF8 pigs was distributed at every 90-min intervals from 0900 to 1930 hours. Data were analyzed using the PROC MIXED procedure with replicate (n = 3), experimental group (n = 4), and their interactions as fixed effects, and the REPEATED statement was used for repeated measures data. Pigs had a similar average daily feed intake (ADFI) during P1 (P > 0.05). In P2, HS–AL and PF8 pigs had lower ADFI (−19%), average daily gain (−25%), and final body weight (−6.1 kg) than TN–AL pigs (P < 0.01). TN–AL pigs had thicker backfat than TN–PF8 pigs (P < 0.05), while the HS pigs had intermediate results. HS pigs had a higher perirenal fat percentage based on the contrast analysis between PF8 pigs (P < 0.05). Thermoregulatory responses of pigs increased with HS exposure but did not differ between HS or between TN groups (P > 0.05). For TN pigs, variation in muscle temperature (Tmuscle) depended on feeding and physical activity, while for HS pigs, Tmuscle gradually increased throughout the day. The Tmuscle of PF8 pigs increased with each additional meal but plateaued earlier for HS–PF8 than TN–PF8 pigs; an increase in Tmuscle per meal was also lower in HS–PF8 than TN–PF8 (P < 0.05). Exposure to HS decreased plasma T3 and T4 (P < 0.05) and increased plasma creatinine (P < 0.05). Between the PF8 groups, HS pigs also had a transient increase in plasma insulin on day 8 (P < 0.05). The effect of HS on FI decreased the growth rate of pigs but there are heat-induced effects, such as altered physiological responses, which might explain the direct HS effects seen in other literature especially in terms of increased adiposity. The increased feed provision frequency in the present study did not improve the HS response of pigs.

The aim of this study was to evaluate the effect of 2 climatic environments (temperate [TEMP] vs. tropical humid [TROP]) on production and thermoregulation traits in growing pigs. A backcross design involving Large White (LW; heat sensitive) and Creole (CR; heat tolerant) pigs was studied. The same 10 F LW × CR boars were mated with related LW sows in each environment. A total of 1,298 backcross pigs ( = 634 pigs from 11 batches for the TEMP environment and = 664 pigs from 12 batches for the TROP environment) were phenotyped on BW (every 15 d from wk 11 to 23 of age), voluntary feed intake (ADFI, from wk 11 to 23), backfat thickness (BFT; at wk 19 and 23), skin temperature (ST; at wk 19 and 23), and rectal temperature (RT; at wk 19, 21, and 23). The feed conversion ratio was computed for the whole test period (11 to 23 wk). The calculation of the temperature-humidity index showed an average difference of 2.4°C between the TEMP and TROP environments. The ADG and ADFI were higher in the TEMP environment than in the TROP environment (834 vs. 754 g/d and 2.20 vs. 1.80 kg/d, respectively; < 0.001). Body temperatures were higher in the TROP environment than in the TEMP environment (35.9 vs. 34.8°C for ST and 39.5 vs. 39.3°C for RT, respectively; < 0.001). Most of the studied traits (i.e., BW, BFT, ADG, ADFI, and RT) were affected by sire family × environment interactions ( < 0.05), resulting in "robust" and "sensitive" families. Our results show a family dependency in the relationships between heat resistance and robustness, suggesting the possibility of finding genotypes with high production and low heat sensitivity. Further research is needed to confirm the genetic × environment interaction and to detect QTL related to heat tolerance.

To view supplementary material for this article, please visit https:/doi.org/10.1017/S175173111600286X; This review summarizes the results from the INRA (Institut National de la Recherche Agronomique) divergent selection experiment on residual feed intake (RFI) in growing Large White pigs during nine generations of selection. It discusses the remaining challenges and perspectives for the improvement of feed efficiency in growing pigs. The impacts on growing pigs raised under standard conditions and in alternative situations such as heat stress, inflammatory challenges or lactation have been studied. After nine generations of selection, the divergent selection for RFI led to highly significant ( P

The present study aimed at investigating the evolution of pigs’ fecal microbiota composition from post-weaning to finishing in a longitudinal analysis. The experiment was conducted on 160 Pietrain × (Large White × Landrace) castrated male and female pigs in two replicates. Feces were collected at 52, 99, 119, 140, and 154 days of age for further 16S rRNA sequencing to analyze the microbiota composition. Pig microbiota evolved strongly from 52 to 99 days of age with an increased abundance of Streptococcaceae and a decreased abundance of Lactobacillaceae. During the finishing stage, microbiota kept evolving at a slower rate. To link the community structure to the performances, the fecal samples were clustered into enterotypes sharing a similar bacterial composition. At 52 days, two enterotypes dominated either by Lactobacillus or by Prevotella–Sarcina were identified. They differed from the two enterotypes determined from 99 to 154 days which were dominated either by Lactobacillus or by Turicibacter–Clostridium sensu stricto. During this time period, 75% of the pigs switched enterotypes. The enterotypes were not related to differences in the overall growth or feeding performance. The enterotype definition was time-dependent and seemed to be related to the sex type at 99 days of age.

Fever is one of the most common clinical signs of infection and systemic inflammation and is an important component of non-specific acute phase response. However, its activation results in increased metabolic rate and energy expenditure with negative consequences on animal growth and feed efficiency. This study aimed at investigating the effect of repeated administrations of Escherichia coli lipopolysaccharide (LPS) on the internal temperature of growing pigs and its associated impact on metabolic heat production. In response to LPS, internal temperature of the animals increased from 38.7 to 40 °C within 150 to 200 min after the LPS administration. The corresponding increase in maintenance energy requirements was estimated in 100 kJ/kg BW0.60/d which is equivalent to 10% of the basal metabolic rate of growing pigs.

Climatic environment is one of the main limiting factors of production efficiency in the swine industry especially in tropical countries. The aim of aim of this study was to evaluate the effects of heat exposure during most of gestation on the growth performance and carcass composition of the offspring. A total of 24 mixed parity sows pregnant sows were housed at thermoneutrality (PTN, 18-24 °C, n=12) or in HS conditions (PHS, 28-34 °C, n=12) from the 7th to the 106th day of gestation. At 70 d of age, 48 females from the 24 litters were selected, moved to two climatic chambers and exposed to TN (18-24 °C) or HS (28-34 °C) conditions. Prenatal HS did not impair growth performance. Postnatal HS reduced by 15 and 11% the average daily feed intake and BW gain, respectively. Changes in lean and fat tissue accretion were observed only when pigs were exposed to both the prenatal and postnatal HS.

Heat stress (HS) compromises efficient production of pigs, in part by increasing oxidative stress and inflammation. Therefore the aim of this experiment was to investigate if supplementation of the anti-oxidants selenium or superoxide dismutase (SOD) could ameliorate HS in the pig. Sixty-four female Large White x Landrace pigs (av. 27.75) were acclimated one of the following diets: control (standard grower diet), selenium (Se, + 0.3 ppm organic Se), recombinant SOD (rSOD, 50 IU/d) and Se plus rSOD (SS) for 14 days under thermoneutral conditions (TN, 200C). All rSOD was administered top dressed in liquid form. Pigs were then moved to climate rooms and housed under TN or heat-stress (8 h 350C, 16h 280C/d) for 3 days and blood, urine and tissue collected for analysis terminally on d3. All data was analysed using an ANOVA with Tukeys post-hoc tests. Heat stress increased respiration rate (RR), reduced blood pCO2 and HCO3-, which coupled with a lower base excess indicated that the pigs were experiencing respiratory alkalosis. Furthermore HS increased rectal and skin temperatures, and reduced thyroid hormone (T4) concentrations, however HSP 27 and 70 concentrations were not influenced. Heat stress increased plasma adiponectin and IL-1b, reduced SOD and TNF-a, while no changes in IL-6 and leptin were observed. The effects of the anti-oxidant diets were that Se and SS increased RR, however parameters of respiratory alkalosis were not negatively influenced. The Se diet reduced T4 independently of HS. No improvement in plasma SOD was observed with the rSOD diets, but rSOD reduced adiponectin in HS pigs and both rSOD and SS reduced IL-6 overall. In conclusion a reduction in inflammatory responses were observed with the antioxidants Se and rSOD, including during HS and therefore may be a useful addition to existing amelioration strategies to ameliorate seasonal heat stress in pigs.

The aim of this study was to evaluate the associated effects of ambient temperature and inflammation caused by repeated administration of Escherichia coli lipopolysaccharide (LPS) on insulin, energy, and AA metabolism. Twenty-eight pigs were assigned to one of the two thermal conditions: thermoneutral (24 °C) or high ambient temperature (30 °C). The experimental period lasted 17 d, which was divided into a 7-d period without LPS (days −7 to −1), and a subsequent 10-d LPS period (days 1 to 10) in which pigs were administered 5 repeated injections of LPS at 2-d intervals. Postprandial profiles of plasma insulin and nutrients were evaluated through serial blood samples taken on days −4 (P0), 4 (P1), and 8 (P2). Before the LPS-challenge (P0), postprandial concentrations of glucose, lactate, Gln, Ile, Leu, Phe, Tyr, and Val were greater in pigs kept at 24 °C than at 30 °C (P < 0.05). In contrast, Arg, Asp, Gly, His, and Met postprandial concentrations at P0 were lower at 24 °C than at 30 °C (P < 0.05). At both 24 and 30 °C conditions, pigs had greater postprandial concentrations of insulin (P < 0.01) and lower concentrations of NEFA (P < 0.01) and α-amino nitrogen (P < 0.05) at P1 and P2 than at P0. Compared with P0, postprandial concentrations of glucose were greater (P < 0.05) at P1 in pigs kept at 24 °C, and at P1 and P2 in pigs kept at 30 °C. At both ambient temperatures, pigs had lower (P < 0.05) postprandial concentrations of Ala, Gly, His, Ile, Leu, Pro, Ser, Thr, Trp, and Val at P1 and P2 than at P0. Arginine postprandial concentration at P1 was lower than at P0 in pigs kept at 24 °C (P < 0.05), whereas no difference was observed in pigs at 30 °C. Relative to P0, Gln and Tyr concentrations were lower at P1 and P2 in pigs kept at 24 °C (P < 0.01), whereas lower Gln concentration was observed only at P2 (P < 0.01) and lower Tyr only at P1 (P < 0.01) in pigs kept at 30 °C. Our study shows a hyperglycemic and hyperinsulinemic state in LPS-challenged pigs and a greater magnitude of this response in pigs kept at 30 °C. Furthermore, LPS caused important changes in BCAA, His, Thr, and Trp profiles, suggesting the role these AA in supporting the inflammatory response. Finally, our results suggest that LPS-induced effects on postprandial profiles of specific AA (Arg, Gln, Phe, and Tyr) may be modulated by ambient temperature.

In summary, heat stress compromises a variety of production parameters in the swine industry including growth, carcass composition, and reproduction. Evidence suggests that maternal exposure to heat stress has long-lasting effects on postnatal offspring performance. The combination of climate change forecasts increased pork production in tropical and subtropical regions of the globe and improved genetic capacity for lean tissue accretion and fecundity, all point to increasingly negative impacts of heat stress on pork production efficiency and quality in the future. Physically modifying the environment is currently the primary abatement strategy that should be utilized to mitigate the negative effects of heat stress, but other approaches include dietary modifications and genetic improvement.

Le dérèglement climatique va accroitre la fréquence d’exposition des populations humaines et animales des zones tempérées à des vagues de chaleur auxquelles elles ne sont pas habituées. L’objectif de cette étude était de déterminer les conséquences d’une exposition chronique à la chaleur sur la truie gestante et sur la santé et la réactivité au stress de sa descendance. Les femelles ont été logées à la thermoneutralité (TN, 18-24°C, n=12) ou en conditions chaudes (CH, 28-34°C, n=12) entre les jours de gestation 7 (G7) et 106 (G106), puis déplacées à la thermoneutralité à G107, le terme étant à G115. Les mesures ont été réalisées sur les truies gestantes, puis sur les porcelets jusqu’à 65 jours d’âge.Pendant la gestation, les truies CH présentaient une température cutanée supérieure aux TN de G9 à G106. Le cortisol salivaire, mesuré à G9, G29, G60 et G106, ne différait pas entre les 2 lots de truies. La durée de gestation n’a pas été influencée par le traitement. A la mise-bas, le poids de naissance (TN : 1368 vs. CH : 1362 ± 41 g), les pourcentages de mort-nés (5,8 %) et de porcelets morts entre 0 et 12h après la naissance (8,7 %) ne différaient pas entre les lots. La mortalité entre 12 et 48h était plus élevée dans le lot CH (CH : 9,4%, TN : 1,0%, P

International audience; Gut microbiota is a key contributor to feed use in monogastric species, in particular via the digestion dietary fibres. Molecular techniques are now available to run large studies and decipher the potential of gut microbiota to improve livestock. Studies on human and mice are more advanced: different factors have been demonstrated to influence the gut microbiota composition and functions, including maternal transmission, environment (diet composition and quantity, humidity and heat), age and physiological status. Studies also evaluated if the host controls its gut microbiota. In pigs, chicken and rabbits, microbiota differences between animals of extreme phenotypes within populations, and between lines divergently selected for specific traits, are reported. Other studies reported that some microbiota abundancies are heritable. Linear mixed models have been used to evaluate its contribution to trait variability, or microbiability, with different data (full vs 16S sequencing of gut or faecal contents) and different variance matrices. They showed significant contribution to production traits, reaching more than 30%. However, confounding effects exist, such as the maternal inheritance of the microbiota and the genetic determinism by the host : many studies show reduction of the genetic additive variance, in addition to reduction of the residual variance with microbiability. Specific datasets, testing a given genetic in different environments or using cross-fostering, are used to better understand the relative contribution of each effect (host genetics and microbiota) to the trait variance, and propose solutions to livestock.

International audience; Microbial population in the gastrointestinal tract plays a central role in health and nutrient digestion. The objective of the present study was to investigate the relationships between microbiota and apparent digestibility coefficients with respect to age and diet. Pigs from Large-White, Duroc or Pietrain breeds were raised under the same housing conditions and fed alternately a low-fiber (LF) and a high-fiber diet (HF) during 4 successive 3-week periods. Data collection for digestibility measurements was achieved during the last week of each period. At the end of each period, fecal microbiota was collected for 16S rRNA gene sequencing. The microbiota remained stable across periods whereas digestibility of energy, crude proteins and cell wall components increased. The microbiota was resilient to diet effect and pigs fed the LF diet were discriminated to those fed the HF diet using 31 predicting OTUs with a mean classification error-rate of 3.9%. Clostridiaceae and Turicibacter were negatively correlated whereas Lactobacillus was positively correlated with protein and energy digestibility coefficients in the LF group. In addition, Lachnospiraceae and Prevotella were negatively correlated with cell wall component digestibility. In contrast, no significant correlation was found between microbiota composition and digestibility coefficients when pigs were fed the HF diet. Interestingly, it was also no longer possible to distinguish animals from different breeds once the animals were fed a HF diet, so that the microbiota could only trace the breed origin in the first period and in the LF group. In our experimental conditions, 3 weeks of adaptation to a new diet seems to be sufficient to observe resilience in growing pigs' microbiota. We demonstrated that fecal microbiota can be used to classify pigs according to their dietary treatment. Some bacteria are favorable or unfavorable to digestibility. This suggests that manipulations of bacterial populations can improve digestibility and feed efficiency.

International audience; In organic agricultural systems, swine and poultry must have access to roughage; in the case of rabbits, roughage must constitute 60% of the diet. Allowing access to forage could be a mechanism for reducing feed-related costs and the need to provide protein via complete feed. One issue is that the nutritional values of different forage types are poorly characterised for these monogastric species. However, based on available data, swine and poultry can at least partially exploit forage-based protein (digestibility: about 50% and 75%, respectively), even though they are not herbivorous. For rabbits, which are herbivorous, the nutritional value of forage is high. Different methods of allowing forage access could be used: turning animals out to grass or through feeding. However, several other issues must be explored before clear recommendations can be made to livestock farmers.; En agriculture biologique, les monogastriques doivent avoir accès à des fourrages grossiers (porcs et volailles) ou que ceux-ci représentent 60 % de leur alimentation (lapins). Les fourrages grossiers constituent une ressource locale disponible dans les systèmes d’élevage biologiques, qui présente un potentiel intéressant (bien que les porcs et les volailles ne soient pas herbivores) pour diminuer le coût alimentaire et le recours à des sources de protéines dans l’aliment complet. Leur valeur nutritionnelle est mal connue mais au vu des résultats disponibles, les porcs et les volailles sont en mesure d’en valoriser les protéines en partie (environ 50 % de digestibilité pour des porcs ; 75 % pour des volailles) alors que les apports énergétiques à attendre sont très faibles. Pour les lapins qui sont des herbivores monogastriques, leur valeur nutritionnelle est élevée. Différents modes de valorisation peuvent être envisagés : pâturage ou distribution à l'auge. En fonction des objectifs et du système d’élevage, une conduite de l’aliment complet avec rationnement et/ou appauvrissement de sa teneur en peut permettre, lorsqu’elle bien maîtrisée, permettre de maintenir des performances techniques élevées en diminuant le coût alimentaire. Cependant, de nombreuses pistes sont encore à explorer avant de proposer des recommandations consolidées aux éleveurs de monogastriques désirant valoriser au mieux les fourrages disponibles sur leur exploitation : niveaux de rationnement, formulation de l’aliment appauvrie en protéines, modalités de distribution, optimisation de la gestion du pâturage, choix des espèces végétales pour favoriser la consommation, en constituent quelques-unes.

Global warming is one of the major environmental threats facing the world in the 21st century. This fact will have a significant impact on pig production due to its direct effects on welfare, health, and performance of pigs. Besides, the effects of high temperatures will presumably become more important over the next decades due to the development of pig production in developing countries mainly located in tropical and subtropical areas, where animals are often exposed to ambient temperatures above their thermal comfort zone. Furthermore, pigs reared in tropical areas are often confronted to sanitary challenges including poor hygiene conditions, lack of respect for sanitary rules, and pathogens. This results in the stimulation of the immune system and, as a consequence, in the production of pro-inflammatory cytokines and neuroendocrine adjustments that, in turn, usually have a negative impact on growth and feed efficiency. Although the effects of high ambient temperature and disease on pig physiology and performance have been well documented in literature, little is known about the associated effects of both factors. This understanding may contribute to a better quantification and comprehension of the physiological and metabolic disturbances occurring in practical conditions of pig production in tropical areas and, more generally, in many other geographic areas that will be influenced by the perspective of global warming. Therefore, the objective of this work is to provide an overview of recent research advances on the physiological responses of growing pigs during acclimation to high ambient temperature and on the potential effects of high ambient temperature on the ability of growing pigs to resist, cope with, or recover from an inflammatory challenge.

International audience; The negative impact of heat stress (HS) on the production performances in pig faming is of particular concern. Novel diagnostic methods are needed to predict the robustness of pigs to HS. Our study aimed to assess the reliability of blood metabolome to predict the sensitivity to chronic HS of 10 F1 (Large White x Creole) sire families (SF) reared in temperate (TEMP) and in tropical (TROP) regions (n = 56 +/- 5 offsprings/region/SF). Live body weight (BW) and rectal temperature (RT) were recorded at 23 weeks of age. Average daily feed intake (AFDI) and average daily gain were calculated from weeks 11 to 23 of age, together with feed conversion ratio. Plasma blood metabolome profiles were obtained by Nuclear Magnetic Resonance spectroscopy ((NMR)-N-1H) from blood samples collected at week 23 in TEMP. The sensitivity to hot climatic conditions of each SF was estimated by computing a composite index of sensitivity (I-sens) derived from a linear combination of t statistics applied to familial BW, ADFI and RT in TEMP and TROP climates. A model of prediction of sensitivity was established with sparse Partial Least Square Discriminant Analysis (sPLS-DA) between the two most robust SF (n = 102) and the two most sensitive ones (n = 121) using individual metabolomic profiles measured in TEMP. The sPLS-DA selected 29 buckets that enabled 78% of prediction accuracy by cross-validation. On the basis of this training, we predicted the proportion of sensitive pigs within the 6 remaining families (n = 337). This proportion was defined as the predicted membership of families to the sensitive category. The positive correlation between this proportion and I-sens (r = 0.97, P < 0.01) suggests that plasma metabolome can be used to predict the sensitivity of pigs to hot climate.

High ambient temperature impacts feed intake, growth, and nutrient utilization in pigs. However, little is known on its effects on immune function and, therefore, on how or if it could modulate the utilization of nutrients in pigs exposed to an inflammatory challenge. The aim of this study was to evaluate the effects of high ambient temperature on energy and nitrogen utilization in pigs submitted to repeated injections of Escherichia coli lipopolysaccharide (LPS). Twenty-eight catheterized and pair-housed female pigs (55 kg BW) were assigned to 1 of the 2 thermal conditions: thermoneutrality (TN, 24°C) or high ambient temperature (HT, 30°C). Within each condition, pigs had a 2-wk adaptation period in climatic-controlled rooms and then were transferred to open-circuit respiration chambers. Pigs remained in respiration chambers for a period of 18 d, which was divided into a 7-d period without LPS (baseline) and a subsequent 11-d period with LPS administration (LPSperiod). The interaction between ambient temperature and period was not significant for most of the traits studied. At baseline, pigs kept at HT had lower ADFI (1,500 vs. 2,003 g/d; P < 0.01) and ADG (449 vs. 684 g/d; P = 0.01) and similar nutrient digestibility compared with those kept at TN. Pigs kept at HT also consumed less ME (1,651 vs. 2,170 kJ · kg BW(-0.60) · d(-1); P = 0.01) and produced less heat (1,146 vs. 1,365 kJ · kg BW(-0.60) · d(-1); P < 0.01) than those kept at TN. Furthermore, HT pigs retained less protein and fat than TN pigs (-61 and -57 g/d, respectively; P < 0.01 and P = 0.01). The LPS challenge reduced (P < 0.01) nitrogen (-13.7 and -7.4 g/d) and ME intake (-594 and -335 kJ · kg BW(-0.60) · d(-1)) in TN and HT conditions, respectively; fecal digestibility of nutrients was not affected by LPS. During the LPSperiod, total heat production (HP) was decreased (P < 0.01) in both TN and HT groups (-190 and -104 kJ · kg BW(-0.60) · d(-1), respectively), in connection with the lower short-term thermic effect of feeding (P = 0.01) and resting HP (P < 0.01). In addition, the LPS induced a reduction in protein (P < 0.01) and fat deposition (P = 0.01) in pigs kept at TN (-79 and -73 g/d, respectively) and at HT (-41 and -44 g/d, respectively). In conclusion, our study confirms that high temperature reduces feed intake, growth performance, and HP. Moreover, our results evidence that irrespective of thermal condition, an inflammatory LPS challenge affects energy utilization through changes in ME intake and maintenance requirements.

The aim of the study was to evaluate the consequences of a divergent selection for residual feed intake (RFI) during growth in a temperate environment (TEMP) on sow performance in a tropical environment (TROP). Sows came from a selection experiment conducted at INRA in which 2 lines were selected for larger (RFI(+)) or smaller (RFI(─)) feed intake than predicted from performance. In the first analysis, a subsample of data obtained in TROP conditions (49 lactations) was compared to those obtained in TEMP on their sibs mated with the same boars (54 lactations). In the second analysis, data obtained in the TROP environment (82 lactations) were analyzed for testing the effect of season (warm vs. hot) and line on sow performance. Except for the lactation length, the interaction between line and climatic environment was not significant for the others traits (P > 0.05). The ADFI expressed per kilogram of litter BW gain tended to be higher in the RFI(+) line bred in the TROP environment (P = 0.080), together with piglet BW at weaning, which tended to be lower (P = 0.080). The ADFI was lower in TROP than in TEMP (4.56 vs. 5.86 kg/d; P = 0.003), with negative consequence on litter BW gain and maternal BW loss. The RFI(-) sows tended to eat less feed than RFI(+) sows during lactation (4.55 vs. 5.86 kg/d; P = 0.099). Litter BW at weaning was higher in the RFI(─) line. The RFI(─) sows ate significantly less feed to produce 1 kg of litter than the RFI(+) sows and tended to lose a larger amount of BW during lactation than the RFI(+) sows (2.40 vs. 3.02 kg/kg and -0.66 vs. -0.39 kg/d, respectively, P < 0.10). Whatever the line, ADFI was reduced by about 21% in the hot season (P < 0.05). Litter BW gain was depressed (P < 0.05) in the hot season (1.72 vs. 2.08 kg/d in the warm season; P = 0.023). Lactation maternal BW loss tended to increase in the hot season (1.10 vs. 0.71 kg/d in the warm season; P = 0.016), but back fat loss remained constant (P = 0.295). In the TROP environment, the amount of feed required to produce 1 kg of litter was not influenced by the line in the warm season (2.53 kg/kg on average; P = 0.99), but it tended to be lower in the RFI(─) line when compared to the RFI(+) line in the hot season (2.06 vs. 3.45 kg/kg; P = 0.050). This higher apparent efficiency in RFI(─) sows was mainly related to greater maternal body reserve mobilization (i.e., BW and back fat losses). In conclusion, selection for low RFI during growth in a TEMP environment did not impair sow and litter performance in tropical conditions.

International audience; The main objectives of the present work were to test the effects of heat stress on blood rheology and to determine whether the responses can change according to the pig breeds. Thirty-six pigs from three pig's lines (n = 12 for each line) with assumed different tolerance to heat stress were compared: Large White (LW, little tolerance), Creole (CR, good tolerance) and LW × CR pigs (produced from a cross between LW and CR lines). In a first period, all pigs were exposed to a 9-d period of thermo-neutral environment (24°C; d-9 to d-1; P0). At the end of P0, six pigs from each line were slaughtered (n = 18). Then in a second period, the remaining pigs (6/breed; n = 18) were exposed to a 5-d period of heat stress (32°C; d + 1 -d + 5; P1) and thereafter slaughtered at d + 5. Rectal and skin temperatures, as well as respiratory rate, were recorded on d-1 and d + 5. At slaughter, blood was sampled for hematological and hemorheological measurements. Heat stress caused a rise of the skin temperature and respiratory rate without any changes in the rectal temperature or on the hematological and hemorheological parameters when all pigs' lines were considered. We observed a pig line effect on blood viscosity at high shear rate (375 s-1) and red blood cell deformability at 30 Pa with CR pigs having lower blood viscosity and higher red blood cell deformability than LW pigs. While the changes of blood viscosity under heat stress did not reach statistical significance in LW and CR lines, blood viscosity (at 375 s-1) increased above the temperate values in the LW × CR line. Red blood cell deformability at 30 Pa was higher in CR pigs exposed to heat stress compared to LW pigs in the same condition. In conclusion, thermal loading caused physiological stress but did not widely change the hematological and hemorheological profiles. Although some blood rheological parameters seem to vary with the pig breeds, the responses to heat stress are very similar.

The present study aimed at describing the impact of a deoxynivalenol (DON) - contaminated diet on microbiota composition. A total of 147 (Large White x Landrace) x Piétrain pigs from two replicates were affected to four different experimental treatments. Pigs in the control group (CC) received a control diet from 99 to 154 days of age. Groups DC, CD, and DD were given the DON-contaminated diet (3.02 mg DON/kg feed) for 7 days at 113, at 134, and at 113 and 134 days of age, respectively. The DON-contaminated diet was formulated with a naturally contaminated corn. The body weight gain and the feed intake were daily recorded from day 99 to 154. Fecal samples were collected at the beginning of the experiment (d99), immediately after the end of the 7-days DON challenges (d119 and 140), and at the end of the experiment (d154) for further 16S rRNA sequencing. During challenge periods, ADFI was decreased by 26% to 32% (P < 0.05) and ADG by 40% to 60% (P < 0.05). Short-term DON challenges induced transient changes in microbiota composition. Two weeks after the end of the DON challenges, this composition went back to control state. Whatever the age, DON challenged pigs could be discriminated from controls in a sparse PLS discriminant analysis based on 88 operational taxonomic units or 27 functional pathways with 16% error-rate. The main predictors raised by this discrimination belonged to Streptococcaceae, Lachnospiraceae and Clostridiaceae families. In our experimental conditions, changes in microbiota composition observed during DON challenges were poorly correlated to changes in ADG and ADFI. This experiment revealed a transient modification of the microbiota composition following the exposition to DON-contaminated diet, with no long-term impact on pigs’ performance. This study is part of the Feed-a-Gene Project funded from the European Union’s H2020 Program (grant 633531).

The present study aimed at predicting feed efficiency (FE) based on fecal microbiota, using partial least square regression (PLSR), sparse PLSR, and random forest regression (RF). Fecal samples from 147 Pietrain x (Large White x Landrace) pigs reared in two consecutive batches were collected at 99 days of age. Daily live body weight and feed intake were individually measured in pigs fed ad libitum with a corn soybean diet. The relative abundances of operational taxonomic units (OTU) resulting from fecal 16S rRNA sequencing were used to build the prediction models of FE between 99 and 113 days. From these data, neither PLSR nor RF models have been validated on external datasets. An important over-fitting has been observed in PLSR. With this aim to test the ability of the methods to retrieve information, synthetic OTU were created to fit an artificial Pearson correlation with FE (r² = 0 to 0.9) and were added among the predictors in the dataset. Artificial OTU correlated above 0.37 with FE improved the prediction in sparse PLSR and RF, and reduced the over-fitting. The best predictions were achieved by sparse PLSR. The present study emphasized the ability of sparse PLSR and RF to build valid prediction models of a quantitative phenotype, based on fecal microbiota composition. Since no OTU was correlated above 0.30 with FE in the real dataset, the power of the prediction methods was not enough to extract useful information from the fecal microbiota. The functional redundancy of the microbiota could explain the lack of relevant information in the real dataset to predict pigs’ quantitative phenotype. These results suggest that the best strategy is to run sparse PLSR only if a correlation higher than 0.37 is observed. This study is part of the Feed-a-Gene Project funded from the European Union’s H2020 Program (grant 633531).

Chantier qualité GA; Total tract digestive utilization of cassava (Manihot esculenta) leaves and leaves + stems, sweet potatoes (Ipomoea batatas) leaves and leaves + stems, cocoyam (Xanthosoma sagittifolium) leaves, and erythrina (Erythrina glauca) leaves was studied in three simultaneous Latin square designs with a total of nine castrated Creole growing pigs. Each dried foliage was included at 200 g/kg in a basal maize-soybean meal diet (MSBM) and the difference method was used to calculate the nutritional value of each of the six foliages. These leaves were characterized by a high fibre content and the presence of some anti-nutritional factors (such as tannins, 0.8–3.1%). Each of the foliage diets was measured on three animals (nine for the MSBM diet). Rate of passage variables of diets were also determined using a pulse dose of ytterbium. Mean retention time in the gastrointestinal tract was shorter (P0.05) for cassava and sweet potatoes. It is concluded that the high fibre content in addition to the presence of tannins are the main limiting factors of these tropical foliages in pig nutrition with a subsequent low energy value.

Castrated males from 2 lines of purebred French Large White obtained from a divergent selection experiment for their residual feed intake (RFI) over 7 generations were measured for their energy utilization during thermal acclimation to increased ambient temperature. The RFI(+) line consumed more feed than predicted from its performance, whereas the RFI- line consumed less feed. Each pig was exposed to 24°C for 7 d (P0) and thereafter to a constant temperature of 32°C for 3 consecutive periods of 7 d (P1, P2, P3). Feed intake, feeding behavior parameters, digestibility, components of heat production (HP; measured by indirect calorimetry in respiration chambers), and energy, nitrogen, fat, and water balance were measured in pigs offered feed and water ad libitum and individually housed in respiratory chambers. Two identical respiratory chambers were simultaneously used, and 5 pigs of each line were measured successively. Whatever the trait, the interaction between line and period was not significant (P > 0.10). On average, ADFI was greater in the RFI+ than in the RFI- line (1,945 vs. 1,639 g/d; P = 0.051) in relation to an increase of the mean size of each feeding bout (128 vs. 82 g/visit; P < 0.001). There was no line effect on nutrient and energy digestibility. Total HP tended to be greater in RFI+ than in RFI- lines (1,279 vs. 1,137 kJ·kg BW-0.60·d-1; P = 0.065), which tended to retain more energy (968 vs. 798 kJ·kg BW-0.60·d-1; P = 0.050). The sensible heat loss was greater in RFI+ compared with the RFI- line (644 vs. 560 kJ·kg BW-0.60·d-1; P = 0.020). The RFI+ pigs consumed more water (+981 vs. 657 g·kg BW-0.60·d-1; P = 0.085) and produced more urine (589 vs. 292 g·kg BW-0.60·d-1; P < 0.001) than RFI- pigs, whereas water evaporation was similar for both lines. On average, ME intake and HP declined by about 38% and 20%, respectively, from P0 to P1 (P < 0.001). In contrast to ME intake, HP gradually decreased (P < 0.05) from P1 to P3 in connection with a reduction of the activity related HP. The evaporative heat loss represented 30% on the total heat loss on P0, and this proportion significantly increased on P1 (61%; P < 0.001) and remained constant thereafter. In conclusion, our results suggest that thermal heat acclimation in pigs is mainly related to a biphasic reduction of HP rather than a change in the ability of losing heat, and it did not significantly differ between RFI+ and RFI- lines despite a decreased HP in the latter ones.