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Colostrum intake, which is critical for piglet survival after birth and growth up to weaning, greatly depends on piglet weight and vitality at birth. Our aim was to identify a set of biological variables explaining individual variations in colostrum intake, preweaning growth and risk of dying. Farrowing traits, morphological traits and colostrum intake were determined for 504 piglets born alive from 37 Landrace × Large White sows. A subset of 203 of these piglets was used to measure plasma neonatal concentrations of metabolites and hormones in blood collected from the umbilical cord at birth. From univariate analyses, we established that colostrum intake was positively associated with plasma neonatal concentrations of IGF-I, albumin, thyroid hormones (P

Neonatal maturity depends on the maternal capacity to provide nutrients for foetal growth. This study aimed to investigate the effects of systemic administration of recombinant porcine somatotropin (pST), one of the main regulators of growth and metabolism, to pregnant gilts during late gestation on circulating nutrients and expression levels of genes in liver and skeletal muscle of their 110-day-old foetuses. Gilts received either daily injections of sterile water (control [CTL] group, n = 15) or of 5 mg of pST (pST group, n = 17) from days 90 to 109 of gestation. At day 110 postconceptus, pairs of foetuses (one of small and one of average size within a litter) were selected. Circulating fructose concentrations were greater, but circulating concentrations of urea were lower in pST than in CTL foetuses. Expression levels of genes involved in carbohydrate and lipid metabolism were more affected by pST treatment in liver than in muscle. Hepatic molecular changes suggest an inhibition of energy-consuming processes (glycogen and lipid biosynthesis) and the activation of energy-producing pathway (mitochondrial oxidation) in pST compared to CTL foetuses. Expression levels of some genes involved in intracellular degradation of proteins were greater in the liver of pST foetuses, and combined with lower uremia, this suggests a higher utilisation of protein sources in pST foetuses than in CTL foetuses. In muscle, molecular changes were mainly observed in the IGF-insulin axis. Altogether, pST-treated gilts seem to have a greater ability to support foetal liver development by the reorientation of energy and protein metabolism.

Abstract Background Health and growth of pigs are affected by the hygiene of housing. Lower growth performance observed in poor hygiene of housing conditions is explained by reduced feed intake and metabolic changes caused by the activation of body defences. In a previous experiment, we reported contrasted average values of body weight gain, concentrations of circulating metabolites, redox and immune indicators in blood of pigs housed in good or poor hygiene conditions during the growing period. This study addressed inter-individual variability in these responses to determine whether a particular blood profile explains average daily gain (ADG) of the pig. Results The data originated from 160 growing pigs, half of which subjected to a hygiene challenge for 6 weeks (W0 to W6) and the others housed in good hygiene conditions. Pigs originated from two lines divergently selected for residual feed intake (RFI). Individual body weights were recorded during this period, and relative ADG (rADGW0-W6) was calculated as the ADG corrected by the initial body weight measured at W0. Blood samples were taken before (W0) and 3 weeks (W3) after the beginning of the challenge. The analysed dataset consisted of 51 metabolites and indicators of immune and inflammatory responses measured on 136 pigs having no missing value for any variables, when calculated as the differences W3 minus W0 in circulating concentrations. An algorithm tested all possible linear regression models and then selected the best ones to explain rADGW0-W6. Six variables were identified across the best models and correlated with rADGW0-W6 with a goodness of fit (adjusted R 2 ) of about 67%. They were changes in haptoglobin, global antioxidant capacity of plasma (Biological Antioxidant Power or BAP), free fatty acids, and 3 amino acids: leucine, tryptophan, and 1-methylhistidine. The effects of housing conditions and RFI lines were comprised in the variables of the selected models and none of these conditions improved accuracy of the predictive models, leading to genericity of the pinpointed metabolic changes in relation to variability of ADG. Conclusions This approach allows us to identify blood variables, whose changes in blood concentrations correlated to ADG under contrasted sanitary conditions.

The process of oxidative stress occurs all over the production chain of animals and food products. This review summarises insights obtained in different farm species (pigs, ruminants, poultry, and fishes) to underpin the most critical periods for the venue of oxidative stress, namely birth/hatching and weaning/start-feeding phase. Common responses between species are also unravelled in periods of high physiological demands when animals are facing dietary deficiencies in specific nutrients, suggesting that nutritional recommendations must consider the modulation of responses to oxidative stress for optimising production performance and quality of food products. These conditions concern challenges such as heat stress, social stress, and inflammation. The magnitude of the responses is partly dependent on the prior experience of the animals before the challenge, reinforcing the importance of nutrition and other management practices during early periods to promote the development of antioxidant reserves in the animal. When these practices also improved the performance and health of the animal, this further confirms the central role played by oxidative stress in physiologically and environmentally induced perturbations. Difficulties in interpreting responses to oxidative stress arise from the fact that the indicators are only partly shared between studies, and their modulations may also be challenge-specific. A consensus about the best indicators to assess pro-oxidative and antioxidant pathways is of huge demand to propose a synthetic index measurable in a non-invasive way and interpretable along the productive life of the animals.

Dietary methionine affects protein metabolism, lean gain and growth performance and acts in the control of oxidative stress. When supplied in large excess relative to growth requirements in diets for pigs, positive effects on pork quality traits have been recently reported. This study aimed to decipher the molecular and biochemical mechanisms affected by a dietary methionine supply above growth requirements in the loin muscle of finishing pigs. During the last 14 days before slaughter, crossbred female pigs (n = 15 pigs/diet) were fed a diet supplemented with hydroxy-methionine (Met5; 1.1% of methionine) or not (CONT, 0.22% of methionine). Blood was sampled at slaughter to assess key metabolites. At the same time, free amino acid concentrations and expression or activity levels of genes involved in protein or energy metabolism were measured in the longissimus lumborum muscle (LM). The Met5 pigs exhibited a greater activity of creatine kinase in plasma when compared with CONT pigs. The concentrations of free methionine, alpha-aminobutyric acid, anserine, 3-methyl-histidine, lysine, and proline were greater in the LM of Met5 pigs than in CONT pigs. Expression levels of genes involved in protein synthesis, protein breakdown or autophagy were only scarcely affected by the diet. Among ubiquitin ligases, MURF1, a gene known to target creatine kinase and muscle contractile proteins, and OTUD1 coding for a deubiquitinase protease, were up-regulated in the LM of Met5 pigs. A lower activity of citrate synthase, a reduced expression level of ME1 acting in lipogenesis but a higher expression of PPARD regulating energy metabolism, were also observed in the LM of Met5 pigs compared with CONT pigs. Principal component analysis revealed that expression levels of many studied genes involved in protein and energy metabolism were correlated with meat quality traits across dietary treatments, suggesting that subtle modifications in expression of those genes had cumulative effects on the regulation of processes leading to the muscle transformation into meat. In conclusion, dietary methionine supplementation beyond nutritional requirements in pigs during the last days before slaughter modified the free amino acid profile in muscle and its redox capacities, and slightly affected molecular pathways related to protein breakdown and energy metabolism. These modifications were associated with benefits on pork quality traits.

Abstract Background Poor hygiene of housing induces a systemic inflammatory response. Because inflammation and oxidative stress are processes that can sustain each other, the ways pigs are able to activate their antioxidant defenses are critical for production performance and health during periods when the immune system is solicited. Selection for production performance can also influence reactive oxygen species (ROS) production and expression levels of genes involved in cellular response to oxidative stress in different tissues. To establish the extent by which poor hygiene and selection for feed efficiency affected redox status, pigs divergently selected for residual feed intake (RFI) were housed in poor or good hygiene during 6 weeks. At the end, blood was collected in all pigs, and half of them were killed for tissue sampling. The remaining pigs were reared in good hygiene conditions during a recovery period of 7–8 weeks. Results At week 6, poor hygiene was associated with a lower total antioxidant capacity assessed by plasma ferric reducing ability in all pigs, and with greater plasma levels of hydrogen peroxides in the high RFI pigs (less efficient). Adipose tissue of high RFI pigs exhibited higher activities of catalase and glutathione reductase, and greater thiobarbituric acid reactive substances (TBARS) concentrations when compared with the low RFI pigs (more efficient). Poor hygiene conditions activated the antioxidant enzymes activities (glutathione reductase, superoxide dismutase and catalase) in adipose tissue of both lines, but led to higher ROS production by mature adipocytes isolated from the high RFI pigs only. In liver and muscle, there were only minor changes in antioxidant molecules due to genetics and hygiene conditions. After the resilience period, adipose tissue of pigs previously challenged by poor hygiene maintained higher antioxidant enzyme activities, and for the high RFI line, displayed higher TBARS concentrations. Conclusions Pigs selected for improved feed efficiency showed a lower susceptibility to oxidative stress induced by poor hygiene conditions. This could led to a lower inflammatory response and less impaired growth when these pigs are facing sanitary challenges during the production period.

Sow environment during gestation can generate maternal stress which could alter foetal development. The effects of two group-housing systems for gestating sows on piglet morphological and physiological traits at birth were investigated. During gestation, sows were reared in a conventional system on a slatted floor (C, 18 sows), demonstrated as being stressful for sows or in an enriched system in larger pens and on deep straw bedding (E, 19 sows). On gestation day 105, sows were transferred into identical individual farrowing crates on a slatted floor. Farrowing was supervised to allow sampling from piglets at birth. In each litter, one male piglet of average birth weight was euthanized immediately after birth to study organ development and tissue traits. Blood samples were collected from 6 or 7 piglets per litter at birth and 2 piglets per litter at 4 days of lactation (DL4). At birth, mean piglet BW did not differ between groups (P > 0.10); however, the percentage of light ( 0.10) between C and E piglets, but the insulin to glucose ratio was greater (P = 0.02) in C than in E piglets. Compared with E piglets, C piglets had a lighter gut at birth (P = 0.01) and their glycogen content in longissimus muscle was lower (P < 0.01). In this muscle, messenger RNA levels of PAX7, a marker of satellite cells and of PPARGC1A, a transcriptional coactivator involved in mitochondriogenesis and mitochondrial energy metabolism, were greater (P < 0.05), whereas the expression level of PRDX6, a gene playing a role in antioxidant pathway, was lower (P = 0.03) in C than in E piglets. Other studied genes involved in myogenesis did not differ between C and E piglets. No system effect was observed on target genes in liver and subcutaneous adipose tissue. On DL4, C piglets exhibited a lower plasma antioxidant capacity than E piglets (P = 0.002). In conclusion, exposure of sows to a stressful environment during gestation had mild negative effects on the maturity of piglets at birth.

In pig husbandry, pregnant females are often exposed to stressful conditions, and their outcomes on maternal and offspring health have not been well evaluated. The present study aimed at testing whether improving the welfare of gestating sows could be associated with a better maternal health during gestation, changes in the composition of lacteal secretions and improvement in piglet survival. Two contrasted group-housing systems for gestating sows were used, that is, a French conventional system on slatted floor (C, 49 sows) and an enriched system using larger pens on deep straw (E, 57 sows). On the 105th days of gestation (DG105), sows were transferred into identical farrowing crates on slatted floor. Saliva was collected from all sows on DG35, DG105 and DG107. Blood samples were collected on DG105 from all sows and on the 1st day of lactation (DL1) from a subset of them (C, n=18; E, n=19). Colostrum and milk samples were collected from this subset of sows at farrowing (DL0) and DL4. Saliva concentration of cortisol was greater in C than in E sows at DG35 and DG105, and dropped to concentrations comparable to E sows after transfer into farrowing crates (DG107). On DG105, plasma concentrations of haptoglobin, immunoglobulins G (IgG) and A (IgA), blood lymphocyte counts and plasma antioxidant potential did not differ between groups (P > 0.10), whereas blood granulocyte count, and plasma hydroperoxide concentration were lower in E than in C sows (P < 0.05). Concentrations of IgG and IgA in colostrum and milk did not differ between the two groups. The number of cells did not differ in colostrum but was greater in milk from E than C sows (P < 0.05). Pre-weaning mortality rates were lower in E than C piglets (16.7% v. 25.8%, P < 0.001), and especially between 12 and 72 h postpartum (P < 0.001). Plasma concentration of IgG was similar in E and C piglets on DL4. In conclusion, differences in salivary cortisol, blood granulocyte count and oxidative stress markers between groups suggested improved welfare and reduced immune solicitation during late gestation in sows of the E compared with the C system. However, the better survival observed for neonates in the E environment could not be explained by variations in colostrum composition.

Abstract Background The degree of adipose tissue development at birth may influence neonatal survival and subsequent health outcomes. Despite their lower birth weights, piglets from Meishan sows (a fat breed with excellent maternal ability) have a higher survival rate than piglets from Large White sows (a lean breed). To identify the main pathways involved in subcutaneous adipose tissue maturation during the last month of gestation, we compared the proteome and the expression levels of some genes at d 90 and d 110 of gestation in purebred and crossbred Large White or Meishan fetuses gestated by sows of either breed. Results A total of 52 proteins in fetal subcutaneous adipose tissue were identified as differentially expressed over the course of gestation. Many proteins involved in energy metabolism were more abundant, whereas some proteins participating in cytoskeleton organization were reduced in abundance on d 110 compared with d 90. Irrespective of age, 24 proteins differed in abundance between fetal genotypes, and an interaction effect between fetal age and genotype was observed for 13 proteins. The abundance levels of proteins known to be responsive to nutrient levels such as aldolase and fatty acid binding proteins, as well as the expression levels of FASN, a key lipogenic enzyme, and MLXIPL, a pivotal transcriptional mediator of glucose-related stimulation of lipogenic genes, were elevated in the adipose tissue of pure and crossbred fetuses from Meishan sows. These data suggested that the adipose tissue of these fetuses had superior metabolic functionality, whatever their paternal genes. Conversely, proteins participating in redox homeostasis and apoptotic cell clearance had a lower abundance in Meishan than in Large White fetuses. Time-course differences in adipose tissue protein abundance were revealed between fetal genotypes for a few secreted proteins participating in responses to organic substances, such as alpha-2-HS-glycoprotein, transferrin and albumin. Conclusions These results underline the importance of not only fetal age but also maternal intrauterine environment in the regulation of several proteins in subcutaneous adipose tissue. These proteins may be used to estimate the maturity grade of piglet neonates.

Abstract Background Because the cost of cereals is unstable and represents a large part of production charges for meat-type chicken, there is an urge to formulate alternative diets from more cost-effective feedstuff. We have recently shown that meat-type chicken source is prone to adapt to dietary starch substitution with fat and fiber. The aim of this study was to better understand the molecular mechanisms of this adaptation to changes in dietary energy sources through the fine characterization of transcriptomic changes occurring in three major metabolic tissues – liver, adipose tissue and muscle – as well as in circulating blood cells. Results We revealed the fine-tuned regulation of many hepatic genes encoding key enzymes driving glycogenesis and de novo fatty acid synthesis pathways and of some genes participating in oxidation. Among the genes expressed upon consumption of a high-fat, high-fiber diet, we highlighted CPT1A, which encodes a key enzyme in the regulation of fatty acid oxidation. Conversely, the repression of lipogenic genes by the high-fat diet was clearly associated with the down-regulation of SREBF1 transcripts but was not associated with the transcript regulation of MLXIPL and NR1H3, which are both transcription factors. This result suggests a pivotal role for SREBF1 in lipogenesis regulation in response to a decrease in dietary starch and an increase in dietary PUFA. Other prospective regulators of de novo hepatic lipogenesis were suggested, such as PPARD, JUN, TADA2A and KAT2B, the last two genes belonging to the lysine acetyl transferase (KAT) complex family regulating histone and non-histone protein acetylation. Hepatic glycogenic genes were also down-regulated in chickens fed a high-fat, high-fiber diet compared to those in chickens fed a starch-based diet. No significant dietary-associated variations in gene expression profiles was observed in the other studied tissues, suggesting that the liver mainly contributed to the adaptation of birds to changes in energy source and nutrients in their diets, at least at the transcriptional level. Moreover, we showed that PUFA deposition observed in the different tissues may not rely on transcriptional changes. Conclusion We showed the major role of the liver, at the gene expression level, in the adaptive response of chicken to dietary starch substitution with fat and fiber.

Pigs selected for high performance may be more at risk of developing diseases. This study aimed to assess the health and performance of two pig lines divergently selected for residual feed intake (RFI) (low RFI (LRFI) v. high RFI (HRFI)) and housed in two contrasted hygiene conditions (poor v. good) using a 2×2 factorial design (n=40/group). The challenge period (Period 1), started on week zero (W0) when 12-week-old pigs were transferred to good or poor housing conditions. At week 6 (W6), half of the pigs in each group were slaughtered. During a recovery period (Period 2) from W6 to W13 to W14, the remaining pigs (n=20/group) were transferred in good hygiene conditions before being slaughtered. Blood was collected every three (Period 1) or 2 weeks (Period 2) to assess blood indicators of immune and inflammatory responses. Pulmonary lesions at slaughter and performance traits were evaluated. At W6, pneumonia prevalence was greater for pigs housed in poor than in good conditions (51% v. 8%, respectively, P

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

Both white and brown adipose tissues are recognized to be differently involved in energy metabolism and are also able to secrete a variety of factors called adipokines that are involved in a wide range of physiological and metabolic functions. Brown adipose tissue is predominant around birth, except in pigs. Irrespective of species, white adipose tissue has a large capacity to expand postnatally and is able to adapt to a variety of factors. The aim of this review is to update the cellular and molecular mechanisms associated with pre- and postnatal adipose tissue development with a special focus on pigs and ruminants. In contrast to other tissues, the embryonic origin of adipose cells remains the subject of debate. Adipose cells arise from the recruitment of specific multipotent stem cells/progenitors named adipose tissue-derived stromal cells. Recent studies have highlighted the existence of a variety of those cells being able to differentiate into white, brown or brown-like/beige adipocytes. After commitment to the adipocyte lineage, progenitors undergo large changes in the expression of many genes involved in cell cycle arrest, lipid accumulation and secretory functions. Early nutrition can affect these processes during fetal and perinatal periods and can also influence or pre-determinate later growth of adipose tissue. How these changes may be related to adipose tissue functional maturity around birth and can influence newborn survival is discussed. Altogether, a better knowledge of fetal and postnatal adipose tissue development is important for various aspects of animal production, including neonatal survival, postnatal growth efficiency and health.

The increasing use of unconventional feedstuffs in chicken’s diets results in the substitution of starch by lipids as the main dietary energy source. To evaluate the responses of genetically fat or lean chickens to these diets, males of two experimental lines divergently selected for abdominal fat content were fed isocaloric, isonitrogenous diets with either high lipid (80 g/kg), high fiber (64 g/kg) contents (HL), or low lipid (20 g/kg), low fiber (21 g/kg) contents (LL) from 22 to 63 days of age. The diet had no effect on growth performance and did not affect body composition evaluated at 63 days of age. Glycolytic and oxidative energy metabolisms in the liver and glycogen storage in liver and Sartorius muscle at 63 days of age were greater in chicken fed LL diet compared with chicken fed HL diet. In Pectoralis major (PM) muscle, energy metabolisms and glycogen content were not different between diets. There were no dietary-associated differences in lipid contents of the liver, muscles and abdominal fat. However, the percentages of saturated (SFA) and monounsaturated fatty acids (MUFA) in tissue lipids were generally higher, whereas percentages of polyunsaturated fatty acids (PUFA) were lower for diet LL than for diet HL. The fat line had a greater feed intake and average daily gain, but gain to feed ratio was lower in that line compared with the lean line. Fat chickens were heavier than lean chickens at 63 days of age. Their carcass fatness was higher and their muscle yield was lower than those of lean chickens. The oxidative enzyme activities in the liver were lower in the fat line than in the lean line, but line did not affect energy metabolism in muscles. The hepatic glycogen content was not different between lines, whereas glycogen content and glycolytic potential were higher in the PM muscle of fat chickens compared with lean chickens. Lipid contents in the liver, muscles and abdominal fat did not differ between lines, but fat chickens stored less MUFA and more PUFA in abdominal fat and muscles than lean chickens. Except for the fatty acid composition of liver and abdominal fat, no interaction between line and diet was observed. In conclusion, the amount of lipids stored in muscles and fatty tissues by lean or fat chickens did not depend on the dietary energy source.

Intrauterine variations in nutrient allowance can alter body composition and tissue features of the porcine offspring around birth. This study aimed to determine the effects of fetal weight variations between littermates and of maternal dietary regimen during gestation on fetal muscle traits just before birth. Fourteen pregnant gilts were reared under a conventional (control, CTL; n=7) or an experimental (treatment, TRT; n=7) dietary regimen during gestation. The dietary treatment provided 70% of the protein and digestible energy contents of the CTL diet during the first 70 days of gestation and then, 115% of the protein and digestible energy contents up to farrowing. At 110 days of gestation, sows were sacrificed and one fetus having a low (824±140 g) and one having a normal (1218±192 g) BW per litter were sampled. Irrespective of maternal dietary regimen, the longissimus muscle of the small fetuses exhibited higher expression levels of DLK1/Pref1 and NCAM1/CD56, two genes known to be downregulated during normal skeletal muscle development. Expression levels of the embryonic isoform of the myosin heavy chain (MyHC), both at the mRNA and at the protein levels, were also higher in small fetuses. In addition, the ratios of perinatal to embryonic and of adult fast to developmental MyHC isoforms were generally lower in light fetuses compared with their medium-weight littermates. These modifications suggest a delayed myofiber development in spontaneous growth-retarded fetuses. Finally, GLUT1 was expressed to a lesser extent in the muscle of small v. normal fetuses, suggesting decreased ability for glucose uptake in muscle. Initial feed restriction and subsequent overfeeding of sows during gestation led to a lower expression of the myogenic factor MYOD1, a prerequisite for myogenic initiation in skeletal muscle. This maternal strategy was also associated with a lower expression level of insulin-like growth factor 1 receptor (IGFR) but an upregulation of IGF2. This suggests an altered susceptibility of muscle cells to IGFs’ signal in fetuses from treated sows. Altogether, intrauterine growth restriction impaired fetal muscle development, and restricted feeding followed by overfeeding of gestating sows did not allow small fetuses to recover normal contractile and metabolic characteristics.

L’amélioration de l’efficacité alimentaire est un enjeu majeur pour la compétitivité de la filière porcine. Elle est classiquement mesurée en élevage par l’indice de consommation, indicateur économique de l’efficacité d’utilisation des aliments pour la croissance. Un critère alternatif indépendant des performances des animaux, la Consommation Moyenne Journalière Résiduelle (CMJR), a été proposé dans les années 1960. Cet article synthétise les résultats obtenus à partir de la sélection divergente de deux lignées à l’INRA, une lignée à CMJR faible, animaux consommant moins que prédit pour leurs besoins de production et d’entretien, et donc plus efficaces, et une lignée à CMJR élevée, animaux consommant plus que prédit pour leurs besoins, moins efficaces. Ces recherches montrent qu’il est possible de sélectionner pour la CMJR chez le porc en croissance avec un impact limité sur les caractères de production et de reproduction femelle, permettant ainsi de diminuer les quantités d’aliments utilisées en élevage. La dégradation des paramètres de qualité technologique de la viande en réponse à l’amélioration génétique de l’efficacité alimentaire est un point de vigilance dans les stratégies de sélection, de même que la composition nutritionnelle de la ration alimentaire. Finalement, la capacité de réponse à des stress ou à des changements de conditions d’élevage ne semble pas affectée par la sélection, contrairement à ce qui est suggéré dans la littérature en réponse à la sélection pour une CMJR réduite. Les défis qui résultent de ces résultats pour poursuivre l’amélioration de ce caractère en production tout en répondant à l’évolution des contraintes de l’élevage sont discutés.

Une production durable nécessite de disposer d’animaux capables de s’adapter à une diversité croissante de contraintes et perturbations environnementales pour maintenir leurs performances de production. La flexibilité métabolique est un des leviers importants pour la compréhension de l’adaptation individuelle aux perturbations externes. Les éléments du métabolisme sont organisés en un réseau biologique vaste et complexe, recouvrant différentes échelles d’organisations spatiales et temporelles. Cet article présent trois formalismes de modélisation permettant de décrire ce réseau et y associe trois exemples illustratifs du comportement de ce réseau face à des perturbations telles que rencontrées en production animale. Ces formalismes dépendent de la taille du (sous)-réseau que l’on souhaite considérer et du type de prédictions souhaitées (qualitatives, quantitatives) : i) la modélisation structurelle qui se base sur l’étude des propriétés topologiques d’un réseau de grande taille, ii) la modélisation stœchiométrique qui permet d’analyser les flux métaboliques dans un état stationnaire et iii) la modélisation dynamique qui permet d’observer l’évolution des acteurs d’un réseau biologique dans le temps.

Intramuscular fat (IMF) content plays a key role in various quality traits of meat. IMF content varies between species, between breeds and between muscle types in the same breed. Other factors are involved in the variation of IMF content in animals, including gender, age and feeding. Variability in IMF content is mainly linked to the number and size of intramuscular adipocytes. The accretion rate of IMF depends on the muscle growth rate. For instance, animals having a high muscularity with a high glycolytic activity display a reduced development of IMF. This suggests that muscle cells and adipocytes interplay during growth. In addition, early events that influence adipogenesis inside the muscle (i.e proliferation and differentiation of adipose cells, the connective structure embedding adipocytes) might be involved in interindividual differences in IMF content. Increasing muscularity will also dilute the final fat content of muscle. At the metabolic level, IMF content results from the balance between uptake, synthesis and degradation of triacylglycerols, which involve many metabolic pathways in both adipocytes and myofibres. Various experiments revealed an association between IMF level and the muscle content in adipocyte-type fatty acid-binding protein, the activities of oxidative enzymes, or the delta-6-desaturase level; however, other studies failed to confirm such relationships. This might be due to the importance of fatty acid fluxes that is likely to be responsible for variability in IMF content during the postnatal period rather than the control of one single pathway. This is evident in the muscle of most fish species in which triacylglycerol synthesis is almost zero. Genetic approaches for increasing IMF have been focused on live animal ultrasound to derive estimated breeding values. More recently, efforts have concentrated on discovering DNA markers that change the distribution of fat in the body (i.e. towards IMF at the expense of the carcass fatness). Thanks to the exhaustive nature of genomics (transcriptomics and proteomics), our knowledge on fat accumulation in muscles is now being underpinned. Metabolic specificities of intramuscular adipocytes have also been demonstrated, as compared to other depots. Nutritional manipulation of IMF independently from body fat depots has proved to be more difficult to achieve than genetic strategies to have lipid deposition dependent of adipose tissue location. In addition, the biological mechanisms that explain the variability of IMF content differ between genetic and nutritional factors. The nutritional regulation of IMF also differs between ruminants, monogastrics and fish due to their digestive and nutritional particularities.

Muscle lipid concentration is known to influence pork eating quality. This study aimed at evaluating the effect of a restriction–re-alimentation feeding strategy on intramuscular fat deposition in pigs. A total of 70 Duroc × (Large White × Landrace) pigs (castrated males and females) were used. Ten pigs were first slaughtered at 30 kg live weight (LW) to determine initial body and muscle composition. From 30 to 80 kg LW (growing period), pigs were either fed ad libitum (AL) or restricted to 70% of the ad libitum intake of AL pigs (RA). From 80 to 110 kg LW (finishing period), both AL and RA pigs were fed ad libitum. In each group, pigs were slaughtered at 80 kg (n = 10) and at 110 kg (n = 20) LW. During the growing period, the growth rate of RA pigs was reduced by 30% (P < 0.001) compared with AL pigs. During the finishing period, RA pigs had a 7% (P = 0.09) higher growth rate than AL pigs due to compensatory feed intake (+14%). Plasma insulin-like growth factor-1 concentration was lower in RA pigs at 80 kg LW, but markedly increased after re-alimentation up to the level observed in AL pigs (P < 0.001). At 80 kg, the leaner carcasses of RA pigs resulted from a more pronounced reduction in fat than in lean tissue deposition rates. Re-alimentation of RA pigs increased fat tissue deposition (+160% for females, P < 0.01) but not lean deposition in the carcass, leading to limited differences in carcass composition between RA and AL pigs at 110 kg LW. Regarding tissue deposition rates, the response to feeding strategy differs between muscles. In the m. biceps femoris (BF), restriction affected lipid (−50%, P < 0.001) and protein (−25%, P < 0.001) deposition, whereas re-alimentation increased lipid (+62%, P < 0.05) but not protein deposition rates. At market weight, the extent of the difference in BF lipid concentration between RA and AL pigs was strongly reduced, but still significant. By contrast, in the m. longissimus, restriction decreased protein but not lipid deposition, whereas neither of them was modified during re-alimentation. Therefore, an increased muscle lipid concentration at 110 kg LW could not be reached in RA pigs. Modifications of onset and/or duration of restriction and re-alimentation periods should be tested to optimise effects on muscle lipid deposition and thereby achieve improved pork quality.

La cause majeure de mortalité néonatale des porcelets est l’hypothermie due à une consommation insuffisante de colostrum. La consommation de colostrum résulte d’interactions complexes entre la truie, le porcelet, la portée et l’environnement. La truie et le déroulement de la gestation peuvent influencer de nombreux facteurs qui jouent un rôle clé dans la prise de colostrum par le porcelet et ses chances de survie, comme son poids, sa maturité et sa vitalité à la naissance, ou la variabilité intra-portée du poids de naissance. La consommation de colostrum dépend aussi de la capacité de la truie à le produire en quantité suffisante pour couvrir les besoins de sa portée. Les stratégies de suralimentation des truies pendant la totalité ou une partie de la gestation pour augmenter le poids ou la maturité des porcelets à la naissance se révèlent généralement inefficaces. L’impact de ces stratégies mériterait néanmoins d’être étudié dans des élevages où les performances zootechniques sont réellement dégradées. Des pistes à explorer concernent la supplémentation des régimes de gestation en certains acides gras ou certains acides aminés. Les supplémentations en composés modulant l’immunité augmentent généralement les teneurs en immunoglobulines du colostrum, mais les conséquences sur la survie néonatale nécessitent d’être étudiées sur le terrain. Enfin, l’alimentation maternelle pendant la gestation et la phase peripartum peut influencer la quantité et la qualité du colostrum consommé par les porcelets nouveau-nés et une attention particulière devra être portée à ce volet dans les recherches futures.

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.

La teneur en lipides intramusculaires est une composante importante de la qualité des produits carnés, et en particulier de leur acceptabilité sensorielle. Les facteurs susceptibles de modifier la quantité de lipides dans les muscles de l’animal au moment de son abattage sont multiples, parmi lesquels son génotype, son type sexuel, son âge et son alimentation. Cependant, les déterminismes métaboliques ou géniques de la teneur en lipides intramusculaires restent mal connus. Des travaux récents montrent que l’importance des flux de lipides dans le muscle et l’orientation d’une balance entre de nombreuses voies impliquées dans la lipogenèse des acides gras d’une part et leur oxydation d’autre part, seraient responsables de l’essentiel de la variabilité de la teneur en lipides intramusculaires durant la période postnatale. Les mécanismes précoces qui président au contrôle du nombre d’adipocytes intramusculaires (c’est-à-dire à la prolifération et différenciation cellulaires) seraient majoritairement à l’origine des différences de teneur en lipides intramusculaires en fonction du génotype de l’animal ou de la sélection génétique intra-race. Les approches à haut débit sans a priori, telles que la transcriptomique et la protéomique, devraient prochainement aboutir à l’identification de nouvelles cibles permettant le contrôle de la teneur en lipides intramusculaires, indépendamment de l’adiposité corporelle des animaux.

L’amélioration génétique des lapins élevés pour la production de viande a porté jusqu’à présent essentiellement sur les critères de reproduction (taille de portée) pour les souches femelles et plus récemment sur les aspects quantitatifs de la production pour les souches mâles, principalement la vitesse de croissance. Cette sélection a ainsi permis de réduire l’âge d’abattage des lapereaux de 2 semaines en 15 ans, tandis que le poids d’abattage variait peu. S’appuyant sur les résultats obtenus dans les comparaisons entre les différentes races ou souches, les attendus étaient une amélioration de l’efficacité alimentaire, une réduction de l’adiposité des carcasses, mais aussi une dégradation des rendements à l’abattage. Paradoxalement, les études génétiques portant sur les qualités de la carcasse ou de la viande et sur les caractéristiques musculaires restent peu fréquentes. Toutefois, il existe maintenant quelques expériences de sélection intra-souche pour la croissance dans lesquelles les réponses corrélées ont été mesurées. Si l’indice de consommation est bien corrélé négativement avec la vitesse de croissance, ces expériences ne valident pas toutes les évolutions attendues en matière de composition corporelle, notamment pour l’adiposité de la carcasse. En revanche, elles suggèrent dans leur ensemble des relations génétiques faibles entre les caractéristiques de la viande et la vitesse de croissance. La sélection actuellement pratiquée sur la vitesse de croissance a donc peu de conséquences sur les qualités de la viande de lapin.

La teneur en lipides d’un tissu est la résultante de plusieurs flux métaboliques (dépôt, synthèse, utilisation). Cet article présente les principales caractéristiques de la synthèse des lipides chez le lapin, dans le muscle comparativement aux tissus adipeux visibles et au foie. Le potentiel de synthèse de novo exprimé par le muscle augmente avec l’âge de l’animal, en parallèle à l’accumulation des triglycérides dans les adipocytes intramusculaires. L’activité des enzymes qui fournissent le NADPH nécessaire à la synthèse des acides gras est réduite si l’animal est soumis à une restriction alimentaire en fin d’engraissement, et ceci en parallèle avec une baisse de la teneur en lipides des muscles. A valeur énergétique égale, la nature des acides gras présents dans le régime alimentaire est sans incidence sur l’activité des enzymes de la lipogenèse, mais peut moduler la quantité et la nature des lipides intramusculaires. Des études ultérieures devront être conduites pour évaluer l’importance respective des différentes voies métaboliques dans la détermination de la teneur finale en lipides des muscles.

La maîtrise de la qualité intrinsèque des muscles constitue aujourd’hui un enjeu pour le maintien de la consommation de viande de lapin en France. L’objet de cet article est de présenter les mécanismes de mise en place, d’évolution, et les facteurs de variation des principales caractéristiques musculaires du lapin. Le lapereau présente un faible degré de maturité musculaire à la naissance. La période postnatale est caractérisée par une augmentation de la taille des fibres, ce qui permet un accroissement de la masse musculaire. Dans le même temps, les caractéristiques qualitatives des fibres musculaires se modifient. Les caractéristiques contractiles présentent ainsi une importante plasticité jusqu’à la fin de la période d’allaitement (1 mois). Les caractéristiques métaboliques se différencient au cours de cette période d’allaitement puis évoluent jusqu’à un état adulte atteint à 2 mois d’âge. La période postnatale se caractérise également par une augmentation de la teneur en lipides du muscle, liée à la mise en réserve de triglycérides dans les adipocytes qui sont groupés le long des faisceaux de fibres. La mise en place de ces adipocytes intramusculaires a lieu au cours de la période d’allaitement, puis leur nombre et leur taille augmentent avec l’âge de l’animal, au moins jusqu’à 5 mois. Les caractéristiques musculaires relèvent pour partie d’un déterminisme génétique mais peuvent être également modifiées par des facteurs d’élevage. Cependant, seules des manipulations précoces (in utero et allaitement) permettraient de contrôler à la fois les caractéristiques qualitatives des fibres musculaires et celles des lipides intramusculaires.

Background: Feed efficiency is a research priority to support a sustainable meat production. It is recognized as a complex trait that integrates multiple biological pathways orchestrated in and by various tissues. This study aims to determine networks between biological entities to explain inter-individual variation of feed efficiency in growing pigs., Results: The feed conversion ratio (FCR), a measure of feed efficiency, and its two component traits, average daily gain and average daily feed intake, were obtained from 47 growing pigs from a divergent selection for residual feed intake and fed high-starch or high-fat high-fiber diets during 58 days. Datasets of transcriptomics (60 k porcine microarray) in the whole blood and metabolomics (1H-NMR analysis and target gas chromatography) in plasma were available for all pigs at the end of the trial. A weighted gene co-expression network was built from the transcriptomics dataset, resulting in 33 modules of co-expressed molecular probes. The eigengenes of eight of these modules were significantly ([Formula: see text]) or tended to be ([Formula: see text]) correlated to FCR. Great homogeneity in the enriched biological pathways was observed in these modules, suggesting co-expressed and co-regulated constitutive genes. They were mainly enriched in genes participating to immune and defense-related processes, and to a lesser extent, to translation, cell development or learning. They were also generally associated with growth rate and percentage of lean mass. In the whole network, only one module composed of genes participating to the response to substances, was significantly associated with daily feed intake and body adiposity. The plasma profiles in circulating metabolites and in fatty acids were summarized by weighted linear combinations using a dimensionality reduction method. Close association was thus found between a module composed of co-expressed genes participating to T cell receptor signaling and cell development process in the whole blood and related to FCR, and the circulating concentrations of polyunsaturated fatty acids in plasma., Conclusion: These systemic approaches have highlighted networks of entities driving key biological processes involved in the phenotypic difference in feed efficiency between animals. Connecting transcriptomics and metabolic levels together had some additional benefits., (© 2023. The Author(s).)