Feeding pigs amino acids as protein-bound or in free form influences postprandial concentrations of amino acids, metabolites, and insulin.

Dietary proteins need to be digested first while free amino acids (AAs) and small peptides are readily available for absorption and rapidly appear in the blood. The rapid postprandial appearance of dietary AA in the systemic circulation may result in inefficient AA utilisation for protein synthesis of peripheral tissues if other nutrients implicated in AA and protein metabolism are not available at the same time. The objective of this experiment was to compare the postprandial concentrations of plasma AA and other metabolites after the ingestion of a diet that provided AA either as proteins or as free AA and small peptides. Twenty-four male growing pigs (38.8 ± 2.67 kg) fitted with a jugular catheter were assigned to one of three diets that provided AA either in protein form (INT), free AA and small peptides (HYD), or as free AA (FAA). After an overnight fast and initial blood sampling, a small meal was given to each pig followed by serial blood collection for 360 min. Postprandial concentrations of plasma AA, glucose, insulin, and urea were then measured from the collected blood. Non-linear regression was used to summarise the postprandial plasma AA kinetics. Fasting concentrations of urea and some AA were higher (P < 0.05) while postprandial plasma insulin and glucose were lower (P < 0.01) for INT than for HYD and FAA. The area under the curve of plasma concentration after meal distribution was lower for INT for most AAs (P < 0.05), resulting in a flatter curve compared to HYD and FAA. This was the result of the slower appearance of dietary AA in the plasma when proteins are fed instead of free AA and small peptides. The flatter curve may also result from more AAs being metabolised by the intestine and liver when INT was fed. The metabolism of AA of the intestine and liver was higher for HYD than FAA. Providing AA as proteins or as free AA and small peptides affected the postprandial plasma kinetics of AA, urea, insulin, and glucose. Whether the flat kinetics when feeding proteins has a positive or negative effect on AA metabolism still needs to be explored.

Postprandial plasma amino acid and metabolite kinetics of adult and growing pigs fed a diet with a balanced or unbalanced amino acid profile.

Feeding diets with an unbalanced amino acid (AA) profile can reduce the postprandial AA utilization for protein synthesis. Growing pigs use dietary AA mainly for protein accretion, whereas non-lactating and non-pregnant adult pigs use AA mainly for maintenance. The requirement for AA for growth is much larger than that for maintenance and growing pigs may therefore be more affected by a diet with an unbalanced AA profile than adult pigs. This study aimed to compare the postprandial plasma AA and metabolite concentrations of adult and growing pigs after feeding a diet with either an unbalanced (UNB) or a balanced AA profile (BAL). The postprandial plasma concentrations of AA were used to study the influence of AA balance on postprandial AA metabolism. Extensively hydrolysed feathers (EHF) were used as an AA source. Both BAL and UNB contained EHF supplemented with L-Ala, L-Asp, L-Glu, Gly, and L-Trp while BAL was also supplemented with L-His, L-Ile, L-Lys, L-Met, and L-Tyr. Four growing and four male adult pigs were fitted with a jugular catheter and received each diet as a meal test thrice. The meal test consisted of giving a small meal after an overnight fast followed by serial blood collection for 360 min. A non-linear regression model was used to describe the postprandial plasma AA kinetics. Plasma kinetics of adult and growing pigs fed BAL resulted in a higher area under the curve (AUC) for the AA that were used to balance the diet. For the other AA, feeding BAL resulted in lower AUC, suggesting faster metabolic utilization of AA for protein synthesis. The apparent quantity of dietary AA appearing in the plasma after feeding was lower in adult pigs, suggesting higher first-pass AA utilization in the intestine and liver. For adult and growing pigs, balancing the AA profile of the diet resulted in faster overall metabolic utilization of AA as seen in the generally lower AUC of BAL compared to UNB.

Review: Implication of redox imbalance in animal health and performance at critical periods, insights from different farm species.

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.

Feeding intact proteins, peptides, or free amino acids to monogastric farm animals.

For terrestrial farm animals, intact protein sources like soybean meal have been the main ingredients providing the required amino acids (AA) to sustain life. However, in recent years, the availability of hydrolysed protein sources and free AA has led to the use of other forms of AA to feed farm animals. The advent of using these new forms is especially important to reduce the negative environmental impacts of animal production because these new forms allow reducing the dietary crude protein content and provide more digestible materials. However, the form in which dietary AA are provided can have an effect on the dynamics of nutrient availability for protein deposition and tissue growth including the efficiency of nutrient utilization. In this literature review, the use of different forms of AA in animal diets is explored, and their differences in digestion and absorption rates are focused on. These differences affect the postprandial plasma appearance of AA, which can have metabolic consequences, like greater insulin response when free AA or hydrolysates instead of intact proteins are fed, which can have a profound effect on metabolism and growth performance. Nevertheless, the use and application of the different AA forms in animal diets are important to achieve a more sustainable and efficient animal production system in the future, as they allow for a more precise diet formulation and reduced negative environmental impact. It is, therefore, important to differentiate the physiological and metabolic effects of different forms of AA to maximize their nutritional value in animal diets.

Flash dietary methionine supply over growth requirements in pigs: Multi-facetted effects on skeletal muscle metabolism.

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.

Identification of blood immune and metabolic indicators explaining the variability of growth of pigs under contrasted sanitary conditions.

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 R2) 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.

A static model to analyze carbon and nitrogen partitioning in the mammary gland of lactating sows.

Quantitative estimates of mammary nutrient inputs, outputs and metabolism in sows are scarce, despite being critical elements to identify parameters controlling milk synthesis central for the feeding of lactating sows. The objective of this study was to quantify the mammary gland input and output of nutrients as well as the intramammary partitioning of carbon and nitrogen with the purpose to identify mechanisms controlling mammary nutrient inputs, metabolism and milk production in lactating sows. A data set was assembled by integration of results from four studies. The data set included data on litter performance, mammary arterial-venous concentration differences (AV-difference) of energy metabolites and amino acids, and the contents of lactose, fat and amino acids in milk. Milk yield was estimated based on average litter size and litter gain, and mammary plasma flow (MPF) was estimated using the sum of phenylalanine and tyrosine as internal flow markers. The yield and composition of milk were used to estimate mammary nutrient output in milk, and MPF and AV-difference were used to estimate net mammary input of carbon and nitrogen and output of CO2. Carbon and nitrogen used for the synthesis of lactose, fat and protein in milk and CO2-yielding processes were represented in a static nutrient partitioning model. The origin of mammary CO2 output was calculated using theoretical estimates of carbon released in processes supporting mammary synthesis of de novo fat, protein and lactose in milk, mammary tissue protein turnover and transport of glucose and amino acids. Results indicated that total input of carbon from glucose and lactate was partitioned into lactose (36%), fat (31%) and CO2-yielding processes (34%). Theoretical CO2 estimates indicated that de novo fat synthesis, milk protein synthesis and mammary tissue protein turnover were the main processes related to mammary CO2 production. More than 90% of mammary gland amino acid input was used for milk protein. The quadratic relationship between AV-difference and mammary input of essential amino acids indicated that both changes in AV-difference and MPF contributed to the regulation of mammary input of essential amino acids. The impact of the arterial supply of amino acids on mammary input may be greater for the branched-chain amino acids, arginine and phenylalanine than for other essential amino acids. In conclusion, relationships between input and output parameters indicate that AV-difference and MPF regulate mammary nutrient input to match the supply and demand of nutrients for the mammary gland.

Tissue-specific responses of antioxidant pathways to poor hygiene conditions in growing pigs divergently selected for feed efficiency.

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.

A systematic literature mapping and meta-analysis of animal-based traits as indicators of production diseases in pigs.

The choice of animal-based traits to identify and deal with production diseases is often a challenge for pig farmers, researchers and other related professionals. This systematic review focused on production diseases, that is, the diseases that arise from management practices, affecting the digestive, locomotory and respiratory system of pigs. The aim was to classify all traits that have been measured and conduct a meta-analysis to quantify the impact of diseases on these traits so that these can be used as indicators for intervention. Data were extracted from 67 peer-reviewed publications selected from 2339 records. Traits were classified as productive (performance and carcass composition), behavioural, biochemical and molecular traits. A meta-analysis based on mixed models was performed on traits assessed more than five times across studies, using the package metafor of the R software. A total of 524 unique traits were recorded 1 to 31 times in a variety of sample material including blood, muscle, articular cartilage, bone or at the level of whole animal. No behavioural traits were recorded from the included experiments. Only 14 traits were measured on more than five occasions across studies. Traits within the biochemical, molecular and productive trait groups were reported most frequently in the published literature and were most affected by production diseases; among these were some cytokines (interleukin (IL) 1-ß, IL6, IL8 and tumour necrosis factor-α), acute phase proteins (haptoglobin) and daily weight gain. Quantification of the influence of factors relating to animal characteristics or husbandry practices was not possible, due to the low frequency of reporting throughout the literature. To conclude, this study has permitted a holistic assessment of traits measured in the published literature to study production diseases occurring in various stages of the production cycle of pigs. It shows the lack of consensus and common measurements of traits to characterise production diseases within the scientific literature. Specific traits, most of them relating to performance characteristics or immunological response of pigs, are proposed for further study as potential tools for the prognosis and study of production diseases.

Impact of hygiene of housing conditions on performance and health of two pig genetic lines divergent for residual feed intake.

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<0.001). Irrespective of hygiene conditions, lung lesion scores were lower for LRFI pigs than for HRFI pigs (P=0.03). At W3, LRFI in poor conditions had the highest number of blood granulocytes (hygiene×line, P=0.03) and at W6, HRFI pigs in poor conditions had the greatest plasma haptoglobin concentrations (hygiene×line, P=0.02). During Period 1, growth rate and growth-to-feed ratio were less affected by poor hygiene in LRFI pigs than in HRFI pigs (hygiene×line, P=0.001 and P=0.02, respectively). Low residual feed intake pigs in poor conditions ate more than the other groups (hygiene×line, P=0.002). Irrespective of the line, fasting plasma glucose concentrations were higher in poor conditions, whereas fasting free fatty acids concentrations were lower than in good conditions. At the end of Period 2, pneumonia prevalence was similar for both housing conditions (39% v. 38%, respectively). During Period 2, plasma protein concentrations were greater for pigs previously housed in poor than in good conditions during Period 1. Immune traits, gain-to-feed ratio, BW gain and feed consumption did not differ during Period 2. Nevertheless, at W12, BW of HRFI previously housed in poor conditions was 13.4 kg lower than BW of HRFI pigs (P<0.001) previously housed in good conditions. In conclusion, health of the most feed efficient LRFI pigs was less impaired by poor hygiene conditions. This line was able to preserve its health, growth performance and its feed ingestion to a greater extent than the less efficient HRFI line.

Comparison of plasma tryptophan-related metabolites in crossbred Piétrain and Duroc pigs.

Besides being incorporated into proteins, Trp, an indispensable AA, is involved in numerous metabolic pathways. Previous data showed that Trp conversion into kynurenine (Kyn) and nicotinamide (Nam) differs among studies, and such differences cannot be explained by different dietary niacin supplies. We hypothesized that pig genotype influences Trp metabolism and thus the conversion of Trp into its metabolites. The objective of this study was to compare plasma appearance of Trp and related metabolites in 12 Duroc and 12 Piétrain crossbred postweaning pigs fed 2 contrasting dietary Trp levels. Within each genotype, 6 pigs were fed a basal (B-Trp: 17% and 15% standardized ileal digestible [SID] Trp:Lys for starter and prestarter diets) or supplemented (S-Trp: 24% and 23% SID Trp:Lys for starter and prestarter diets) Trp diet. Growth was monitored, and plasma fasted concentrations were measured over 4 wk, and then pigs were fitted with a jugular catheter for frequent blood samplings. After overnight fasting, 350 g of the experimental diets were offered to each pig, and plasma concentrations of Trp, Kyn, Nam, and 5-hydroxytryptamine (5-HT) were measured for 6 h. The activities of Trp-degrading enzymes were measured in different tissues collected after pig slaughtering. Plasma Trp fasted concentrations did not differ between B-Trp and S-Trp diets and increased from weaning to 2 and 4 wk after weaning for Piétrain but not for Duroc crossbred pigs (time × genotype, = 0.001). Plasma Kyn concentrations were greater 4 wk after weaning ( = 0.002) than at weaning and for Piétrain compared to Duroc genetics ( = 0.008). Plasma Nam concentrations were greater for pigs fed the S-Trp diet than for those fed the B-Trp diet ( = 0.0001) and for Duroc than for Piétrain genetic lines ( = 0.001); this difference tends to be greater at weaning than after ( = 0.055). Our data showed an increase in plasma concentrations of Trp, Kyn, Nam, and 5-HT according to time after a meal and to the dietary Trp content. However, postprandial plasma concentrations of Trp metabolites and enzyme activities were not significantly different between Duroc and Piétrain crossbred pigs. In conclusion, our results suggest that Nam endogenous synthesis capacity from Trp is greater in Duroc than in Piétrain crossbred pigs, but this was apparent only at weaning.

Impact of feed restriction and housing hygiene conditions on specific and inflammatory immune response, the cecal bacterial community and the survival of young rabbits.

Limiting the post-weaning intake of the young rabbit is known to improve its resistance to digestive disorders, whereas a degradation of its housing hygiene is assumed to have a negative impact on its health. This study aims at providing insights into the mechanism of digestive health preservation regarding both host (growth and immune response) and its symbiotic digestive microbiota. A 2×2 factorial design from weaning (day 28) to day 64 was set up: ad libitum intake or restricted intake at 70% of ad libitum, and high v. low hygiene of housing (n=105 per group). At day 36 and day 45, 15 animals/group were subcutaneously immunized with ovalbumin (OVA) to assess their specific immune response. Blood was sampled at 36, 45, 57 and 64 days of age to determine total and anti-OVA immunoglobulin type G (IgG) and haptoglobin levels. The cecal bacterial community was explored (18 per group) by 454 pyrosequencing of genes coding for the 16S ribosomal RNA, whereas cecal pH, NH3 and volatile fatty acid (VFA) concentrations were measured to characterize fermentative activity. A 30% reduction in feed intake reduced the growth by only 17% (P<0.001), and improved the feed conversion ratio by 15% (P<0.001), whereas the degradation of hygiene conditions slightly decreased the feed intake in ad libitum fed rabbits (-3.5%, P<0.02). As poor hygiene conditions did not affect weight gain, feed conversion was improved from day 42 (P<0.05). Restricted feeding led to a lower mortality between day 28 and day 40 (P=0.047), whereas degraded hygiene conditions decreased overall morbidity (7.8% v. 16.6%; P<0.01). Both a reduced intake and low hygiene conditions of housing affected microbiota composition and especially dominant genera belonging to the Ruminococcaceae family (P<0.01). Moreover, low hygiene was associated with a higher Ruminococcaceae/Lachnospiraceae ratio (3.7 v. 2.4; P<0.05). Cecal total VFA and pH were increased (+19%; P<0.001) and decreased (-0.1 pH unit; P<0.05), respectively, in feed-restricted rabbits. Neither specific anti-OVA IgG nor haptoglobin was affected by treatments. Total IgG concentrations were the highest in animals raised in poor hygiene conditions after 8 days of restriction, but decreased after 19 days of restriction in high hygiene conditions (-2.15%; P<0.05). In conclusion, the degradation of hygiene conditions failed to induce a systematic specific and inflammatory response in rabbit, but reduced morbidity instead. Our results suggest that the microbiota composition would be a helpful source of biomarkers of digestive health.

Influence of the inflammatory status of entire male pigs on their pubertal development and fat androstenone.

Androstenone production increases during pubertal development and plays a major role in boar taint. The objective of the present study was to evaluate the effect of a subclinical inflammation on the pubertal development of boars and hence on fat androstenone. Contrasted hygiene conditions were applied during rearing to increase the variability of the inflammatory status. Boars from a commercial cross line were allocated at 139±0.9 days of age (Day 0) and 81.3±5.9 kg of live weight either to Good (n=61) or Poor (n=54) hygiene conditions until slaughter at 172.9±4.8 days of age and 116.7±4.5 kg live weight. Inflammatory status, growth and pubertal development were evaluated on Day 0, Day 27 and at slaughter by analysing the blood formula, plasma inflammatory proteins; testosterone and oestradiol, salivary cortisol, rectal temperature, live weight, back fat thickness, weight of reproductive organs and clinical scores of organs (lungs, stomach, snout). Fat was collected on Day 27 by biopsy and at slaughter to measure androstenone concentration. A principal component analysis including inflammatory indicators followed by a clustering procedure was performed to identify pigs with a high (Infl+, n=50) or a low (Infl-, n=65) inflammatory status. Infl+ pigs had more granulocytes/ml, higher concentrations of haptoglobin, C-reative protein and cortisol (P<0.05), lower growth rate and higher lung pneumonia score. However, regardless of stage, the inflammatory status had no significant effect on plasma testosterone or oestradiol, fat androstenone or sexual organ development. Present data suggest that a mild inflammatory status has no influence on pubertal development or fat concentration of androstenone in boars.

Metabolic response to an inflammatory challenge in pigs divergently selected for residual feed intake.

Selection for residual feed intake (RFI), which is used to select animals for feed efficiency, also influences nutrient partitioning between growth and maintenance functions. This study was designed to investigate if selection for reduced RFI can alter the trade-off between growth and immunity and contributes to differences in metabolic responses to an inflammatory challenge. Piglets from 2 lines divergently selected on RFI (low: RFI, = 10, and high: RFI, = 11) were challenged at 55 d of age (on d 0) with complete Freund's adjuvant (CFA) to induce a noninfectious pneumonia. Plasma haptoglobin and nutrient concentrations (in fasted state and 2 h after feeding) were determined from d -1 to d 7, and tissue protein metabolism was determined on d 8. Haptoglobin concentrations were greater from d 1 to d 7 relative to d -1 ( < 0.01). Feed intake was less on d 1 than on the other days ( < 0.001), as was total AA plasma concentrations at fasted state ( < 0.05). Fasted concentrations of His ( = 0.06) and Trp ( = 0.05) tended to be less, those of Val were less ( < 0.05), and fed concentrations of Lys were increased ( < 0.05) on d 7 compared to d -1. Uremia was less on d 7 than on d -1 at fasted state ( < 0.05), whereas it did not vary at fed state ( 0.1). Fasted glucose and insulin plasma concentrations were stable across days ( 0.1). In the fed state and in only RFI pigs, glucose concentration was greater on d 1 than on d 3, 5, and 7 ( < 0.05). Total AA, Gln, Ile, Leu, Pro ( < 0.05), and hydroxyproline ( = 0.07) were less in RFI than RFI pigs at fed state, whereas Ala and Gly were less in RFI pigs at fasted and fed states ( < 0.05). Citrulline ( < 0.05) and Met ( < 0.01) concentrations were greater in RFI than RFI pigs in the fasted state, whereas Asp was greater in RFI pigs in both fasted and fed states ( < 0.05). On d 8, liver and LM protein synthesis tended to be lower ( = 0.07 and 0.09, respectively) and liver calpain activity was greater ( = 0.07) in RFI than RFI pigs. Liver and LM proteasome did not differ between lines ( 0.1). The metabolic differences between lines were not associated with differences in feed intake, ADG between d -1 and d 8, and haptoglobin concentration ( 0.1). Thus, it seems that that, using different metabolic strategies, both lines coped similarly with the CFA challenge. Contrary to our hypothesis, this experiment showed, in young pigs, no advantage of RFI animals in response to an inflammatory challenge.

[Pubertal maturation, physical self-esteem and sexuality in a sample of French adolescents]. / Influence de la maturation pubertaire et de l'estime de soi corporelle sur la sexualité à l'adolescence.

AIM: The aim of this study was to explore the links between pubertal maturation, physical self-esteem and sexuality in adolescence, differentiating between boys and girls. METHOD: The sample was comprised of 312 French secondary school children (seventh and ninth grades); 52.6 % (n=164) of whom were girls. Participants answered three self-evaluation questionnaires: the scale of sexuality (interests, emotions, relationships: IERS) in prime adolescence (12 to 15 years); (b) the self-administered rating scale for pubertal development and (c) the Physical Self-Description Questionnaire (PSDQ). RESULTS: Pubertal maturation was associated with higher scores on "Flirting with the aim of having sexual relations" and "Going out with someone", and a drop in overall and physical self-esteem, mainly in socially valued domains, namely "Body fat" for girls, and "Strength" and "Health" for boys. Overall physical self-esteem was associated with "Going out with someone" and "Flirting with the aim of having sexual relations" in boys. DISCUSSION: Physical changes at puberty induce two distinct trends in adolescents: sexual exploration and discovery (genitalized body), and self-depreciation (social body).

Effect of inflammation stimulation on energy and nutrient utilization in piglets selected for low and high residual feed intake.

Selection of animals for improved feed efficiency can affect sustainability of animal production because the most efficient animals may face difficulties coping with challenges. The objective of this study was to determine the effects of an inflammatory challenge (using an intravenous injection of complete Freund's adjuvant - CFA) in piglets from two lines of pigs divergently selected during the fattening period for a low (RFI-) or a high (RFI+) residual feed intake (RFI; difference between actual feed intake and theoretical feed requirements). Nitrogen and energy balances (including heat production - HP - and its components: activity-related HP - AHP, thermic effect of feeding, and resting HP) were measured individually in thirteen 20-kg BW castrated male piglets (six and seven from RFI+ and RFI- line, respectively) fed at the same level (1.72 MJ ME/kg BW0.60 per day) from 3 days before to 3 days after CFA injection. Dynamics of dietary U-13C-glucose oxidation were estimated from measurements of 13CO2 production on the day before and 3 days after the CFA injection. Oxidation of dietary nutrients and lipogenesis were calculated based on HP and O2 consumption and CO2 production. The data were analyzed as repeated measurements within piglets in a mixed model. Before CFA injection, RFI- piglets had a lower resting energy expenditure than RFI+ piglets, which tended to increase energy retention because of a higher energy retention as fat. The CFA injection did not affect feed intake from the day following CFA injection onwards but it increased energy retention (P=0.04). Time to recover 50% of 13C from dietary glucose as expired 13CO2 was higher in RFI+ piglets before inducing inflammation but decreased after to the level of RFI- piglets (P<0.01). Oxidation of U-13C-glucose tended to slightly increased in RFI- piglets and to decreased in RFI+ piglets (P=0.10) because of CFA. Additionally, RFI- piglets had a lower respiratory quotient during the 1st day following the CFA injection whereas RFI+ piglets tended to have a higher respiratory quotient. In conclusion, selection for RFI during the fattening period also affected the energy metabolism of pigs during earlier stages of growth. The effects of CFA injection were moderated in both lines but the most efficient animals (RFI-) exhibited a marked re-orientation of nutrients only during the 1st day after CFA, and seemed to recover thereafter, whereas the less efficient piglets expressed a more prolonged alteration of their metabolism.

Performance of piglets in response to the standardized ileal digestible phenylalanine and tyrosine supply in low-protein diets.

Reducing the CP level of the diet allows for a reduction in N excretion without limiting performance as long as the amino acid (AA) requirements are covered. The availability of crystalline AA has permitted for a considerable reduction in the CP level of diets, practically used in pig nutrition. The adoption of low CP diets and the extent to which the CP content can be reduced further depends on the knowledge of the minimum levels of indispensable AA that maximize growth. The standardized ileal digestible (SID) Phe : Lys and Tyr : Lys requirements and the possibility to substitute Tyr by Phe have never been studied in piglets. The objectives of this study were to estimate these requirements in 10 to 20 kg pig as well as to determine the extent to which Phe can be used to cover the Tyr requirement. In three dose-response studies, six pigs within each of 14 blocks were assigned to six low CP diets (14.5% CP) sub-limiting in Lys at 1.00% SID. In experiment 1, the SID Phe : Lys requirement estimate was assessed by supplementing a Phe-deficient diet with different levels of l-Phe to attain 33%, 39%, 46%, 52%, 58%, and 65% SID Phe : Lys. Because Phe can be used for Tyr synthesis, the diets provided a sufficient Tyr supply. A similar approach was used in experiment 2 with six levels of l-Tyr supplementation to attain 21%, 27%, 33%, 39%, 45% and 52% SID Tyr : Lys. Phenylalanine was supplied at a level sufficient to sustain maximum growth (estimated in experiment 1). The SID Phe : Lys and SID Tyr : Lys requirements for maximizing daily gain were 54% and 40% using a curvilinear-plateau model, respectively. A 10% deficiency in Phe and Tyr reduced daily gain by 3.0% and 0.7%, respectively. In experiment 3, the effect of the equimolar substitution of dietary SID Tyr by Phe to obtain 50%, 57%, and 64% SID Phe : (Phe+Tyr) was studied at two limiting levels of Phe+Tyr. From 57% to 64% SID Phe : (Phe+Tyr), performance was slightly reduced. In conclusion, it is recommended not to use a Phe+Tyr requirement in the ideal AA profile but rather use a SID Phe : Lys of 54% and a SID Tyr : Lys of 40% to support maximal growth.

Impact of feed restriction on health, digestion and faecal microbiota of growing pigs housed in good or poor hygiene conditions.

Feed restriction could be a relevant strategy to preserve gut health, reduce systemic inflammatory response and finally limit antibiotic use. This study assessed the effect of feed restriction on growing pigs submitted to a moderate inflammatory challenge induced by the degradation of the environmental hygiene that is known to alter growth rate. The experiment was run on 80 pigs selected at 7 weeks of age according to a 2×2 factorial design: two feeding levels, ad libitum (AL) and feed restricted (FR) at 60% of AL, and two conditions of environmental hygiene, clean and dirty. Pigs were housed individually throughout the experiment. From 61 to 68 days of age (day 0 to 7), pigs were housed in a post weaning unit and feed restriction was applied to half of the pigs from day 0 to day 29. At 68 days of age (day 7 of the experiment), pigs were transferred in a growing unit where half of FR and half of AL pigs were housed in a dirty environment (poor hygiene) and the other half in a clean environment (good hygiene) until day 42. Growth performance was recorded weekly. Blood and faeces samples were collected to measure indicators of inflammation, nutrient digestibility and microbiota composition. Faecal consistency was monitored daily to detect diarrhoeas. Feed restriction decreased daily weight gain (-35% to -50%, P<0.001), increased the feed conversion ratio (+15%, P<0.001) and CP digestibility (+3%, P<0.05) and reduced the occurrence of diarrhoeas irrespective of hygiene conditions. Poor hygiene conditions decreased growth performance (-20%, P<0.05) and total tract digestibility of all nutrients (P<0.001). Haptoglobin (+50%) concentrations and lymphocyte (+10%) and granulocyte (+40%) numbers were higher in poor hygiene conditions (P<0.05), confirming that the model was effective to induce a systemic inflammatory response. Both feed restriction and hygiene modified the profile of the faecal microbiota. In this study, feed restriction did not reduce the systemic inflammatory response caused by poor hygiene conditions despite the limitation of the occurrence of digestive disorders. However, our study opens discussions regarding the impact of hygiene and feed restriction on gut microbial communities and digestive health.

Meal frequency changes the basal and time-course profiles of plasma nutrient concentrations and affects feed efficiency in young growing pigs.

Ingested dietary nutrients and feed energy are partitioned among tissues to sustain body growth. Based on the respective costs of the various metabolic pathways allowing use and storage of feed energy into cells, it may be theorized that daily meal frequency could affect growth, body composition or feed efficiency. This study aimed to determine the effects of daily meal frequency on nutrient partitioning, tissue metabolism and composition, and performance. Young growing pigs (30 kg BW) were offered a same amount of feed either in 2 (M2, n = 15) or 12 (M12, n = 16) meals per day during a 3-wk interventional period. Animals fed twice a day had an accelerated weight gain (+6.4%, P < 0.05) and exhibited a greater G:F (+4%, P = 0.03) than animals fed 12 meals per day during this period. Basal plasma concentrations of glucose, lactate, triglyceride, urea, and leptin were lower (P < 0.001) in M2 pigs than in M12 pigs. Meal frequency also changed (P < 0.001) the time-course profiles of plasma concentrations of glucose, insulin, and lactate in response to meal ingestion. A greater rise and a sharper fall in plasma glucose and insulin levels were observed in M2 pigs compared with M12 pigs. In both groups, similarities were observed in the postprandial time courses of plasma concentrations of insulin and of α-amino nitrogen (used as a measure of total AA). Despite these metabolic responses, tissue lipids, glycogen content, and enzyme activities participating in energy metabolism in muscle and liver were similar (P > 0.10) in both groups at the end of the trial. Percentage of perirenal fat in the body and depth of dorsal subcutaneous fat tissue were not affected by meal frequency, but kidney weight was lower (-18%, P < 0.001) in M2 pigs than in M12 pigs. Altogether, the less frequent daily meal intake improves the conversion of feed into weight gain, without marked modifications of tissue composition in young pigs.

The use of free amino acids allows formulating very low crude protein diets for piglets.

Reducing the dietary CP level with free AA supplementation allows reduction of N excretion and the risk of gut disorders while maintaining performance of pigs. We have recently reevaluated the Val, Ile, His, and Leu requirements in pigs, which enables formulating very low CP diets. However, requirements for undifferentiated N, and thus the extent to which the dietary CP content can be reduced, are unknown. Two experiments were conducted to test the effect of reducing the dietary CP content to meet an ideal AA profile on N retention and performance in 10- to 20-kg pigs. In the first experiment, we measured N retention in 6 blocks of 4 pigs each, all receiving diets with 1.15% standardized ileal digestible (SID) Lys. Each pig within a block was allotted to different levels of dietary CP (19.7%, 16.8%, 14.0%, and 12.7%). The reduction of CP content from 19.7% to 16.8% had no impact on N retention and decreased N excretion by 29%. A further decrease in CP content to 14.0% and 12.7% resulted in a reduced N retention (P < 0.01). In the second experiment, we measured performance in 14 groups of 6 pigs each, allotted to 6 levels of dietary CP with 1.00% SID Lys with soybean meal (17.6%, 15.6%, 13.5%, and 11.8%) or without soybean meal (14.0% and 13.0%). Decreasing the dietary CP content from 17.6% to 13.5% had no effect on performance. Daily gain was reduced in pigs receiving the 11.8% CP diet (P < 0.01). Feeding the diet formulated without soybean meal with 13.0% CP content resulted in reduced feed efficiency, but the addition of Glu to increase the CP content from 13.0% to 14.0% restored performance (P < 0.01). In conclusion, the use of L-Val, L-Leu, L-Ile, L-His, and L-Phe enables a 4% unit reduction in the CP content relative to SID Lys in diets for pigs. Soybean meal can be totally replaced using cereals and free AA. However, a further reduction in dietary CP:Lys level below 13.5% reduces feed efficiency, indicating that the supply of N for the synthesis of dispensable AA may be a limiting factor for the performance of pigs.