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La production porcine est responsable d’environ 10 % des émissions de gaz à effet de serre (GES) de l’élevage mondial et doit réduire ses impacts. Ces émissions de GES, comptabilisées en sortie de ferme, sont liées à la production d’aliment et la gestion des effluents, pour 60 % et 30 % respectivement. La réduction du taux de protéines alimentaires peut agir sur ces deux sources. Cette revue synthétise les connaissances actuelles sur les bénéfices de cette stratégie pour réduire l’impact changement climatique (CC) en relation avec les matières premières utilisées et la réduction des émissions azotées. Une analyse de cycle de vie (ACV) à l’échelle de l’aliment montre que le CC est réduit de 8 % par point de réduction du taux protéique, grâce au remplacement des matières premières plus impactantes (produits du soja). Ces bénéfices sont dépendants des matières premières disponibles et utilisées, du choix des bases de données d’évaluation environnementale et du contexte technico-économique. La modélisation des émissions azotées en fonction des performances, mise à jour par méta-analyse, permet d’effectuer une ACV en sortie de ferme. Une réduction du CC par kg de porc de 10 % pour un point de baisse du taux protéique est atteignable. Cependant, des lacunes méthodologiques et de connaissances subsistent pour correctement évaluer cette stratégie : facteurs d’émission du N2O, prise en compte de l’utilisation des effluents pour la fertilisation, effet sur les performances zootechniques. Par ailleurs, des évolutions structurelles sont nécessaires pour faciliter la mise en pratique, comme la rémunération des externalités positives.

Nitrogen (N) excretion and emissions can be reduced in fattening pigs by reducing dietary crude protein (CP) levels. Effects of this strategy are well documented for moderate CP reduction, but little literature exists on further CP reduction made possible by free isoleucine, histidine, and leucine. This trial evaluated the effects of 2 levels of reduction in CP on growth performance, N balance, and gaseous emissions. Forty-eight pigs were allocated to 12 gaseous emission-measuring chambers at 28 kg live weight. Three dietary treatments (CTRL; −1.2pt; −2.4pt), with a CP content, respectively, of 18.1%, 16.9%, and 15.0% in phase 1 (28 to 48 kg) and 16.1%, 15.0%, and 13.8% in phase 2 (48 to 80 kg), were fed ad libitum. Growth performance was recorded for each phase. Body lipid and protein composition were analyzed by dual-energy X-ray absorptiometry in 2 animals per chamber at the beginning and end of the trial. These results were used to calculate the N balance. Slurry volume and composition were measured at the end of the trial. Ammonia, methane, and nitrous oxide emissions were recorded continuously. Data were analyzed with a general linear model including the linear and quadratic effect of CP reduction and phase as fixed effects. A trend for a quadratic effect of CP reduction on feed intake was observed (P =  0.085) with a decrease from CTRL to −1.2pt and then an increase with the −2.4pt treatment. Daily gain and gain to feed were improved by the low CP diets in phase 1 but were degraded in phase 2 (phase × CP interaction, P <  0.001) while body composition was not affected. Nitrogen excretion decreased with CP reduction (linear effect, P =  0.023) but tended to plateau with the low CP diets (quadratic effect, P =  0.081). Methane emissions per kg of gain were reduced with CP reduction (linear effect, P =  0.031). Ammonia emissions decreased with CP reduction, mostly in phase 1 (phase × CP interaction, P =  0.015); however, the emission factor (g N-NH3 / g urinary N) was not affected. Nitrous oxide emissions were not affected by CP reduction and its emission factor (g N-N2O / g N) tended to increase (linear effect, P =  0.07). Slurry ammonia-N decreased (linear effect, P <  0.023; quadratic effect, P =  0.049), but other slurry components were not significantly impacted. In this trial, a plateau in N excretion and emission reduction was reached with the −2.4pt treatment. Nevertheless, it is important to study such a reduction in conditions closer to commercial ones. [ABSTRACT FROM AUTHOR]

Dietary supplementation with arginine (Arg) or glutamine (Gln) has been considered as an option to improve nursing performance in reproductive sows. This study investigated whether a low-level supplementation of Arg or Gln or a blend of both could modify milk nutrients and improve piglets' growth beyond weaning. Seventy-two multiparous sows were assigned to four groups: one group fed a control diet, three treatment groups fed the control diet supplemented with either 0.35% Arg, 0.35% Gln, or both, from day 108 of gestation until weaning at day 26 of lactation. Immediately after birth, the litters were cross fostered to 13 piglets and monitored until 2 wk after weaning. Sows body condition and litter growth were assessed. Colostrum and milk samples were collected for nutrient analyses. Plasma concentrations of insulin-like growth factor 1 (IGF-1) around weaning were determined in sows and two representative piglets per litter. Supplementing Gln or the combination of Arg and Gln had no effect on the parameters studied. Arg supplementation increased weaning weight, while decreasing the variation of piglet weights 2 wk after weaning. There was no correlation with plasma IGF-1 since the hormone was not altered in sows or piglets. The colostral concentration of fat tended to increase in the Arg-group, whereas protein, lactose, energy, and polyamine concentrations remained unaffected. Milk samples obtained on day 12 and 25 of lactation were not influenced by dietary treatment. The data indicate that there might be a window of opportunity, explicitly at the onset of lactation, for dietary intervention by maternal dietary Arg supplementation. [ABSTRACT FROM AUTHOR]

An experiment was conducted to test the hypothesis that excess dietary Leu affects metabolism of branched-chain amino acids (BCAA) in growing pigs. Forty barrows (initial body weight [BW]: 30.0 ± 2.7 kg) were housed individually in metabolism crates and allotted to 5 dietary treatments (8 replicates per treatment) in a randomized complete block design. The 5 diets were based on identical quantities of corn, soybean meal, wheat, and barley and designed to contain 100%, 150%, 200%, 250%, or 300% of the requirement for standardized ileal digestible Leu. Initial and final (day 15) BW of pigs were recorded. Daily feed consumption was also recorded. Urine and fecal samples were collected for 5 d following 7 d of adaptation to the diets. At the end of the experiment, blood and tissue samples were collected to analyze plasma urea N (PUN), plasma and hypothalamic serotonin, tissue BCAA, serum and tissue branched-chain α-keto acids, and messenger ribonucleic acid abundance of genes involved in BCAA metabolism. Results indicated that acid detergent fiber, average daily feed intake, and gain-to-feed ratio decreased (linear, P < 0.05) as dietary Leu increased. A trend (linear, P = 0.082) for decreased N retention and decreased (linear, P < 0.05) biological value of dietary protein was also observed, and PUN increased (linear, P < 0.05) as dietary Leu increased. A quadratic reduction (P < 0.05) in plasma serotonin and a linear reduction (P < 0.05) in hypothalamic serotonin were observed with increasing dietary Leu. Concentrations of BCAA in liver increased (linear, P < 0.001), whereas concentrations of BCAA in skeletal muscle decreased (linear, P < 0.05) as dietary Leu increased. Concentration of α-ketoisovalerate was reduced (linear and quadratic, P < 0.001) in liver, skeletal muscle, and serum, and α-keto-β-methylvalerate was reduced (linear, P < 0.001; quadratic, P < 0.001) in skeletal muscle and serum. In contrast, α-keto isocaproate increased (linear, P < 0.05) in liver and skeletal muscle and also in serum (linear and quadratic, P < 0.001) with increasing dietary Leu. Expression of mitochondrial BCAA transaminase and of the E1α subunit of branched-chain α-keto acid dehydrogenase increased (linear, P < 0.05) in skeletal muscle as dietary Leu increased. In conclusion, excess dietary Leu impaired growth performance and nitrogen retention, which is likely a result of increased catabolism of Ile and Val, which in turn reduces availability of these amino acids resulting in reduced protein retention, and excess dietary Leu also reduced hypothalamic serotonin synthesis. [ABSTRACT FROM AUTHOR]

The introduction of precision feeding in sows depends on a precise estimation of its potential benefits. The goal of this study was to evaluate the effects of precision feeding and feed intake during gestation on gilt performances during two gestation cycles. Four isoenergetic treatments were compared: two constantconcentration feeding strategies (0.53% Lys DIS), one with constant feed intake (FF; flat feeding) and the other variable (BF; "bump feeding", with decreased feed intake before 90 days of gestation, then greater feed intake until parturition), and two precisionfeeding strategies based on the InraPorc model, one by parity (APP) and the other considering the body weight of the gilt at breeding (API). A total of 333 gilts were followed from breeding to weaning for two gestation and lactation cycles. Body weight and backfat depth were measured at breeding, 90 days of gestation, parturition, and weaning. Feed consumption was monitored daily. Litter variables were measured as birth and weaning weight, mortality, and overall gain. A mixed model was used to analyze differences between the four treatments using the sow as the experimental unit. Results showed that APP gilts gained more body weight during the gestation than FF gilts (65.1 vs 61.7 kg; P = 0.01) but no difference remained at the end of lactation (P > 0.10). Mobilization of backfat depth was more important during lactation in the APP group compared with FF and BF treatments (3.4 vs 2.9 mm; P = 0.03). BF and APP gilts had greater total birth litter weight than API gilts (400 g and 600 g greater, respectively), with FF gilts being intermediate (P = 0.02). However, the effect faded out with no difference on weaning weight and overall lactation gain weight (P > 0.10). The APP gilts had more weaned piglets than BF or FF gilts (+0.6 piglet, P = 0.01). During the second cycle, API sows gained more body weight during gestation than FF sows (58.8 vs 55.7 kg; P = 0.05). Yet, no significant difference was observed at the end of lactation. For the backfat depth, API sows had greater backfat depth during gestation than FF sows (1.83 vs 1.1 mm; P = 0.05) and a greater mobilization during lactation (2.68 vs 2.0 mm; P = 0.08). No effect was seen on litter mortality. In the same way, no significant effect was observed in the litter performances (P > 0.1). Initial results from this study seem to show a benefit of precision feeding for gilts, but with less effect for their second parity. However, no clear benefit was observed from the bump feeding strategy. [ABSTRACT FROM AUTHOR]

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, P = 0.001). Plasma Kyn concentrations were greater 4 wk after weaning (P = 0.002) than at weaning and for Piétrain compared to Duroc genetics (P = 0.008). Plasma Nam concentrations were greater for pigs fed the S-Trp diet than for those fed the B-Trp diet (P = 0.0001) and for Duroc than for Piétrain genetic lines (P = 0.001); this difference tends to be greater at weaning than after (P = 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. [ABSTRACT FROM AUTHOR]

The present experiment aimed to determine if Trp metabolism and growth responses to dietary Trp are modulated by dietary niacin (B3) in weanling piglets. Piglets weaned at 3 wk of age were distributed 1 wk later (7.6 kg of BW, SEM = 0.1) in 52 pens of 2 animals each. Pens were assigned to factorial dietary treatments with 2 additions of B3, 15 mg/kg (LB3) vs. 45 mg/kg (HB3) and 2 additions of Trp, 0 mg/kg (-Trp) vs. 1 mg/kg (+Trp) for Trp to Lys ratios of 0.16 vs. 0.24, respectively. Growth performance was recorded every week from 4 to 10 wk of age. Fasting blood samples were taken at 4, 6, 8, and 10 wk of age. From 4 to 10 wk of age, ADFI tended to be greater (P = 0.10) in HB3 than in LB3 (1,031 vs. 1,003 g, SEM = 7), and this was reflected (P = 0.06) by ADG (642 vs. 623 g, SEM = 7). No treatment effect was observed on plasma Trp or kynurenine (Kyn), an intermediate metabolite of Trp catabolism. The response of plasma nicotinamide (Nam), a product of Trp catabolism and an indicator of B3 status, to dietary B3 differed according to treatments (interaction Trp x B3, P < 0.01) with values of 1.4, 3.3, 4.1, and 5.3 µM (SEM = 0.1) in LB3-Trp, HB3-Trp, LB3+Trp, and HB3+Trp, respectively. At 11 wk of age, postprandial blood samples were collected from 6 piglets per treatment for measurements of Trp and insulin metabolism. Postprandial plasma Trp (96.4 vs. 72.2 µM, SEM = 3.4) and Kyn (1.7 vs. 1.3 µM, SEM = 0.1) were greater (P < 0.01) in +Trp vs. -Trp. Postprandial plasma Nam was greater (P < 0.01) in +Trp vs. -Trp (3.4 vs. 1.9 µM, SEM = 0.3) and in HB3 vs. LB3 piglets (3.4 vs. 1.9 µM, SEM = 0.3). Postprandial peaks and areas under curves of C-peptide and glucose were not affected by treatments. However, for insulin, the postprandial peak was lower in +Trp vs. -Trp piglets in the LB3 group (interaction Trp x B3, P < 0.05); values were 1.3, 1.0, 0.7, and 1.0 nM (SEM = 0.1) in LB3-Trp, HB3-Trp, LB3+Trp, and HB3+Trp, respectively. The peak value of the molar ratio insulin:Cpeptide was lower (P < 0.02) in +Trp vs. -Trp piglets (0.56 vs. 0.73, SEM = 0.05). The responses observed on growth performance and plasma Nam suggest that the LB3 level was suboptimal. According also to plasma Nam, it appears that supplemental dietary B3 can attenuate Trp oxidation toward niacin metabolites. Postprandial profiles of insulin and C-peptide indicate that Trp action is exerted on insulin clearance rather than on insulin secretion in piglets, without apparent consequences on glucose utilization. [ABSTRACT FROM AUTHOR]

For a calculation of diets covering the pig's requirement and to avoid the waste of valuable nutrients without impact on zootechnical performance, the knowledge about the nutrient contents and their availability of the used feedstuffs, is a prerequisite. From the perspective of sustainability, higher usage of industrial by-products would be desirable to reduce the strong competition for food between human and pig nutrition. Hence, the aim of the present study was to test the effect of high amounts of wheat middlings in pig diets under consideration of the net energy system on zootechnical and slaughter performance of fattening pigs. Four dietary treatments differing in energy- (corn/barley/wheat middlings) and protein source (soybean meal /rapeseed meal / DDGS) were conducted, resulting in one high dietary crude protein treatment (soybean meal) and three reduced dietary crude protein treatments (rapeseed meal, low wheat middlings and high wheat middlings). Animals receiving the high wheat middlings diet showed a significantly lower daily feed intake (-13.6%) compared to the diet including rapeseed meal (p<0.0001). The rapeseed meal diet declined the feed to gain ratio (+8.6%) compared to the other treatments (p<0.05). The average daily gain was numerically greater for pigs receiving the high protein diet (+6.4%; p<0.1) compared to the other treatments. No differences between treatments were recorded for the investigated slaughter parameters. Specific slaughter parameters showed the highest Pearson correlation coefficient with the daily net energy intake. The observed differences regarding zootechnical performance parameters can be explained by unbalanced nutrient contents between the different experimental diets. The net energy system appears to be the most precise tool for an energy estimation of fattening pig diets. An accurate knowledge of the nutrient contents and availability of the feedstuffs is a prerequisite to optimize balanced diets for fattening pigs. [ABSTRACT FROM AUTHOR]

The hypothesis that excess dietary Leu affects growth performance and metabolism of branched-chain amino acids (BCAA) in growing pigs was tested. Forty barrows (30.0 ± 2.7 kg) were placed in metabolism crates and randomly allotted to 5 diets that contained 100, 150, 200, 250, or 300% of the requirement for standardized ileal digestible Leu. Initial and final body weight of pigs and daily feed provisions were recorded. Urine and fecal samples were collected for 5 d to measure N balance and biological value of diets. At the conclusion of the experiment, blood, brain, liver, and muscle samples were collected and average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F) were calculated. Orthogonal polynomial contrasts were used to determine linear and quadratic effects of increasing Leu in the diets. Results indicated that ADG, ADFI, and G:F decreased (linear, P < 0.05) as dietary Leu increased (Table 1). A trend (linear, P = 0.082) for decreased N retention and decreased (linear, P < 0.05) biological value of protein was also observed. Plasma urea N increased (linear, P < 0.05) and a quadratic reduction (P < 0.05) in plasma serotonin and a linear reduction (P < 0.05) in cerebral serotonin were observed with increasing dietary Leu. Concentrations of BCAA in liver increased (linear, P < 0.001), concentrations of BCAA in muscle decreased (linear, P < 0.05), concentration of α-keto-isovalerate was reduced (linear and quadratic, P < 0.001) in liver, muscle, and serum, and α-keto-β-methylvalerate was reduced (linear and quadratic, P < 0.001) in muscle and serum, whereas α-keto-isocaproate increased (linear, P < 0.05) in liver and muscle, and in serum (linear and quadratic, P < 0.001) with increasing dietary Leu. In conclusion, excess dietary Leu reduced growth performance and cerebral serotonin and tended to reduce protein synthesis. [ABSTRACT FROM AUTHOR]

Branched chain amino acids (BCAA), valine (Val), isoleucine (Ile) and leucine (Leu) share the same metabolic pathways. An excess of Leu stimulates the catabolism of Val and Ile that may lead to a decrease in piglet growth performance. The objective of this study is to quantify the response of piglets to dietary Val and the influence of Leu and Ile on this response through a meta-analysis approach. A total of 16 articles published between 2001 and 2018, including 23 experiments and 126 treatments were used. Multiple regression models were fitted with the MIXED procedure of Minitab software with the random effect of the experiment. The Y variables were Average Daily Gain (ADG), Average Daily Feed Intake (ADFI) and Feed Conversion Ratio (FCR). The main X variable was the Standardized Ileal Digestible Val (ValSID) and the other ones were Leu (LeuSID) and Ile (IleSID). The response of ADG, ADFI and FCR to ValSID was curvilinear (P< 0.001: ADG, R2 = 0.93%; ADFI, R2= 0.97%; FCR, R2=0.93%). Results showed that increasing dietary LeuSID reduced ADG and ADFI (P< 0.05) but also that the response of piglets to ValSID was stronger in high LeuSID diet (P < 0.05; Interaction ValSIDxLeuSID; ADG and ADFI). Based on these models, increasing dietary ValSID from 7 to 8.5g/kg generates in wheat-based diets (10 g/kg of LeuSID) an improvement of ADG of 4.7% and ADFI of 2.5% compared to 7.4% for ADG and 5.2% for ADFI in corn-based diets (14 g/kg of LeuSID). The response of ADG, ADFI and FCR to ValSID was not modified by IleSID. This study showed that ADG, ADFI and FCR are improved with increasing dietary Val and this effect was modulated by dietary Leu content except for FCR. Results can help piglet nutritionists to optimize dietary Val levels based on other BCAA content. [ABSTRACT FROM AUTHOR]

Abstract: Healthy weaned pigs susceptible to enterotoxigenic Escherichia coli F4 (ETEC) require more tryptophan (Trp) to maximize their performance. This may be related to an effect on intestinal microbiota. We studied the intestinal bacterial diversity of healthy pigs with different susceptibility to ETEC and fed different Trp levels. Thirty-six littermate weaned pigs were selected to obtain a set potentially formed of 50% ETEC-susceptible and 50% non-susceptible pigs, based on a Mucin 4 gene polymorphism. Pigs were fed a diet with 0.17 (TrpL) or 0.22 (TrpH) standardized ileal digestible Trp:Lys ratio for 21 days. Slaughtered pigs were classified into non-susceptible, mildly susceptible, and susceptible, by testing ETEC adhesion to intestinal villi. Bacterial diversity in jejunum content was assessed by the 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE) fingerprinting analysis and expressed by the Shannon index. Susceptible pigs had a reduced bacterial diversity, particularly with TrpL diet (p =0.003). The ETEC adhesion class affected the quantification of enterobacteria DNA (p =0.027). One DGGE band, which referred to Clostridium bartlettii, was not evidenced in all the susceptible pigs; less DNA from this microbe was quantified by RT-PCR in the jejunum from TrpH susceptible pigs (p =0.025) compared to TrpL. The gene expression for β-galactoside α-2,3-sialyltransferase 1 was higher in jejunal tissue of ETEC-susceptible pigs (p =0.019). In studies on pig gut microbiota, the presence of intestinal receptors for ETEC should be considered because of their contribution to a reduced bacterial diversity. This effect could be partially reversed by dietary Trp addition. [Copyright &y& Elsevier]

The aim of this study was to quantify the response of broilers and piglets to dietary valine (Val) level and the impact of the 2 other branched-chain amino acids (BCAA), leucine (Leu) and isoleucine (Ile), on this response through a meta-analysis approach. The databases were composed of 23 articles published between 1999 and 2018 and included 44 experiments and 229 treatments for broilers and 16 articles published between 2001 and 2018 and including 23 experiments and 126 treatments for piglets. Multiple regression models were fitted with the MIXED procedure of Minitab software with the random effect of the experiment. The Y variables were average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR). The main X variable was dietary standardized ileal digestible Val (SID Val) and the other ones were dietary standardized ileal digestible Leu (SID Leu) and dietary standardized ileal digestible Ile (SID Ile). The response for ADG and ADFI to SID Val was positive linear and quadratic for broilers and piglets (broilers, ADG: P < 0.001, R2 = 0.66; ADFI: P < 0.001, R2 = 0.50; piglets, ADG: P < 0.001, R2 = 0.93; ADFI: P < 0.001, R2 = 0.97). The FCR was reduced linearly (P < 0.001) and quadratically (P < 0.001) with increasing SID Val for broilers (P < 0.001, R2 = 0.80) and piglets (P < 0.001, R2 = 0.93). Increasing dietary SID Leu reduced ADG and ADFI in broilers and piglets (ADG and ADFI, P < 0.05), with only an effect on FCR for broilers (P < 0.05). Results also showed that the response to SID Val was stronger with the highest SID Leu diets for both species (Interaction SID Val×SID Leu: Broilers, ADG and ADFI, P < 0.001; Piglets: ADG and ADFI, P < 0.05). In broilers, increasing SID Ile, resulted in a negative effect on ADG (P < 0.05), on FCR (P < 0.001) and a tendency to negatively affected ADFI (P = 0.08). For both species, the response of ADG, ADFI and FCR to SID Val was not modified by SID Ile (No interaction). The current study showed that ADG and ADFI increases with increasing SID Val and this effect was modulated by Leu except for FCR. • Branched-chain amino acids share the same metabolism and must be studied together. • Response of growth performance to valine linear and quadratic in both species. • High leucine reduced the response to valine in terms of feed intake and weight gain. • Leucine primarily affects feed intake mechanism rather than a feed efficiency. • Isoleucine did not affect the response to valine in both species. [ABSTRACT FROM AUTHOR]

Dietary supplementation with arginine (Arg) or glutamine (Gln) has been considered as an option to improve nursing performance in reproductive sows. This study investigated whether a low-level supplementation of Arg or Gln or a blend of both could modify milk nutrients and improve piglets' growth beyond weaning. Seventy-two multiparous sows were assigned to four groups: one group fed a control diet, three treatment groups fed the control diet supplemented with either 0.35% Arg, 0.35% Gln, or both, from day 108 of gestation until weaning at day 26 of lactation. Immediately after birth, the litters were cross fostered to 13 piglets and monitored until 2 wk after weaning. Sows body condition and litter growth were assessed. Colostrum and milk samples were collected for nutrient analyses. Plasma concentrations of insulin-like growth factor 1 (IGF-1) around weaning were determined in sows and two representative piglets per litter. Supplementing Gln or the combination of Arg and Gln had no effect on the parameters studied. Arg supplementation increased weaning weight, while decreasing the variation of piglet weights 2 wk after weaning. There was no correlation with plasma IGF-1 since the hormone was not altered in sows or piglets. The colostral concentration of fat tended to increase in the Arg-group, whereas protein, lactose, energy, and polyamine concentrations remained unaffected. Milk samples obtained on day 12 and 25 of lactation were not influenced by dietary treatment. The data indicate that there might be a window of opportunity, explicitly at the onset of lactation, for dietary intervention by maternal dietary Arg supplementation., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The physiology of the sow mammary gland is qualitatively well described and understood. However, the quantitative effect of various biological mechanisms contributing to the synthesis of colostrum and milk is lacking and more complicated to obtain. The objective of this study was to integrate physiological and empirical knowledge of the production of colostrum and milk in a dynamic model of a single sow mammary gland to understand and quantify parameters controlling mammary gland output. In 1983, Heather Neal and John Thornley published a model of the mammary gland in cattle, which was used as a starting point for the development of this model. The original cattle model was reparameterized, modified, and extended to describe the production of milk by the sow mammary gland during lactation and the prepartum production of colostrum as the combined output of immunoglobulins (Ig) and milk. Initially, the model was reparameterized to simulate milk synthesis potential of a single gland by considering biological characteristics and empirical estimations of sows and piglets. Secondly, the model was modified to simulate more accurately the responses to changes in milk removal rates. This was done by linking the ejectable milk storage capacity to the number of secretory cells rather than being constant throughout lactation. Finally, the model was extended to include the prepartum synthesis of milk and the kinetics of Ig into and out of the mammary gland. A progressive capacity of secretory cells to synthesize milk was used to differentiate the time between the onset of milk synthesis and Ig transfer. Changes in maximum milk removal rate, duration of milk ejection, and nursing interval exerted a great impact on the modeled milk output. Changes by ±60% in one of these parameters were capable of increasing milk output by 28% to 39% during the first 4 wk in lactation compared with the reference parameterization. This suggests that the ability of the piglet to remove milk from the gland exerts a key control on milk synthesis during lactation. Modeling colostrum as the combined output of Ig and milk allowed to represent the rapid decline in Ig concentration observed during the first hours after farrowing. In conclusion, biological and empirical knowledge was integrated into a model of the sow mammary gland and constitutes a simple approach to explore in which conditions and to what extent individual parameters influence Ig kinetics and milk production., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

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.