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Weaning of piglets is associated with important changes in gut structure and function resulting from stressful events such as separation from the sow, moving to a new facility and dietary transition from a liquid to a solid feed. This may result in post-weaning diarrhoea and a decrease in feed intake and growth. In humans, the cyanobacterium Spirulina platensis (SP) and the freshwater microalga Chlorella vulgaris (CV) are known for their beneficial health effects. This study aimed to determine the effects of early oral administration of Spirulina and Chlorella in piglets on mucosal architecture and cytokine expression in the intestine around weaning, and consequences on growth performance and diarrhoea incidence. The experiment was conducted on 108 suckling piglets of 14 days of age (initial BW=4.9±0.7 kg) and weaned at 28 days of age (day 0). Animals received orally 385 mg/kg BW per day of SP or CV, or water (negative control (NC)) during 4 weeks from day −14 to day 14 and their growth performance was measured daily. After weaning, growth, feed intake and diarrhoea incidence were measured daily. Intestinal morphology and functionality were assessed at day −1, day 2, and day 14. During the suckling period, average daily gain (ADG) in SP piglets was higher, resulting in a higher weaning BW compared to NC and CV piglets (P <0.05). No significant difference between treatments was observed for ADG, average daily feed intake, and gain to feed (G : F) ratio after weaning, but the extent of growth retardation after weaning was the lowest in piglets supplemented with Chlorella (P <0.01). Supplementation with Spirulina reduced diarrhoea incidence by 50% from day 0 to day 14 (P <0.05). Mucosal architecture at the jejunum was unaffected by Spirulina or Chlorella administration (P >0.10). Shorter ileal villi were measured in SP and CV piglets than in NC piglets (P <0.05). Cytokine expression did not differ between treatments in response to weaning. At day 14, IL-8 expression in the ileum was higher in SP piglets, while IL-1 β expression in the jejunum was higher in CV piglets (P <0.05). This study shows that Spirulina administration around weaning alleviates diarrhoea in weaned piglets, without marked modulation of local inflammation. [ABSTRACT FROM AUTHOR]

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<0.001) line differences for RFI (−165 g/day in the low RFI (LRFI) line compared with high RFI line) and daily feed intake (−270 g/day). Low responses were observed on growth rate (−12.8 g/day, P<0.05) and body composition (+0.9 mm backfat thickness, P=0.57; −2.64% lean meat content, P<0.001) with a marked response on feed conversion ratio (−0.32 kg feed/kg gain, P<0.001). Reduced ultimate pH and increased lightness of the meat (P<0.001) were observed in LRFI pigs with minor impact on the sensory quality of the meat. These changes in meat quality were associated with changes of the muscular energy metabolism. Reduced maintenance energy requirements (−10% after five generations of selection) and activity (−21% of time standing after six generations of selection) of LRFI pigs greatly contributed to the gain in energy efficiency. However, the impact of selection for RFI on the protein metabolism of the pig remains unclear. Digestibility of energy and nutrients was not affected by selection, neither for pigs fed conventional diets nor for pigs fed high-fibre diets. A significant improvement of digestive efficiency could likely be achieved by selecting pigs on fibre diets. No convincing genetic or blood biomarker has been identified for explaining the differences in RFI, suggesting that pigs have various ways to achieve an efficient use of feed. No deleterious impact of the selection on the sow reproduction performance was observed. The resource allocation theory states that low RFI may reduce the ability to cope with stressors, via the reduction of a buffer compartment dedicated to responses to stress. None of the experiments focussed on the response of pigs to stress or challenges could confirm this theory. Understanding the relationships between RFI and responses to stress and energy demanding processes, as such immunity and lactation, remains a major challenge for a better understanding of the underlying biological mechanisms of the trait and to reconcile the experimental results with the resource allocation theory. [ABSTRACT FROM PUBLISHER]

• Postprandial plasma amino acid concentrations influence protein metabolism. • A modelling approach can be used to study postprandial amino acid metabolism. • Contrasting plasma amino acid kinetics after feeding proteins and free amino acids. • Visceral amino acid utilisation was higher when feeding protein-bound amino acids. • Amino acids supplied as free from in the diet appear faster in the plasma. 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. [ABSTRACT FROM AUTHOR]

• Unbalanced dietary amino acids affect plasma postprandial amino acid concentrations. • Postprandial plasma amino acid kinetics was used to study amino acid metabolism. • Modelling postprandial amino acid kinetics allows estimation of first metabolism. • Higher first-pass amino acid metabolism of adult pigs compared to growing pigs. • Faster decline of plasma amino acid concentrations when feeding a balanced diet. 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. [ABSTRACT FROM AUTHOR]

Improvement of feed efficiency in pigs has been achieved essentially by increasing lean growth rate, which resulted in lower feed intake (FI). The objective was to evaluate the impact of strategies for improving feed efficiency on the dynamics of FI and growth in growing pigs to revisit nutrient recommendations and strategies for feed efficiency improvement. In 2010, three BWs, at 35±2, 63±9 and 107±7 kg, and daily FI during this period were recorded in three French test stations on 379 Large White and 327 French Landrace from maternal pig populations and 215 Large White from a sire population. Individual growth and FI model parameters were obtained with the InraPorc® software and individual nutrient requirements were computed. The model parameters were explored according to feed efficiency as measured by residual feed intake (RFI) or feed conversion ratio (FCR). Animals were separated in groups of better feed efficiency (RFI− or FCR−), medium feed efficiency and poor feed efficiency. Second, genetic relationships between feed efficiency and model parameters were estimated. Despite similar average daily gains (ADG) during the test for all RFI groups, RFI− pigs had a lower initial growth rate and a higher final growth rate compared with other pigs. The same initial growth rate was found for all FCR groups, but FCR− pigs had significantly higher final growth rates than other pigs, resulting in significantly different ADG. Dynamic of FI also differed between RFI or FCR groups. The calculated digestible lysine requirements, expressed in g/MJ net energy (NE), showed the same trends for RFI or FCR groups: the average requirements for the 25% most efficient animals were 13% higher than that of the 25% least efficient animals during the whole test, reaching 0.90 to 0.95 g/MJ NE at the beginning of the test, which is slightly greater than usual feed recommendations for growing pigs. Model parameters were moderately heritable (0.30±0.13 to 0.56±0.13), except for the precocity of growth (0.06±0.08). The parameter representing the quantity of feed at 50 kg BW showed a relatively high genetic correlation with RFI (0.49±0.14), and average protein deposition between 35 and 110 kg had the highest correlation with FCR (−0.76±0.08). Thus, growth and FI dynamics may be envisaged as breeding tools to improve feed efficiency. Furthermore, improvement of feed efficiency should be envisaged jointly with new feeding strategies. [ABSTRACT FROM PUBLISHER]

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

Residual feed intake (RFI) is defined as the difference between the observed ADFI and the ADFI predicted from production and maintenance requirements. The objectives of this study were to evaluate RFI as a selection criterion to improve feed efficiency and its potential to reduce N and P excretion in 4 pig breeds. Data were collected between 2000 and 2009 in French central test stations for 2 dam breeds [French Landrace (LR) and Large White (LWD)], and 2 sire breeds [Large White (LWS) and Piétrain (PP)]. Numbers of recorded pigs were 6407, 10,694, 2342, and 2448 for the LR, LWD, LWS, and PP breeds, respectively. All PP animals were genotyped for the halothane mutation. This data set was used to calculate RFI equations for each of the 4 breeds, and to estimate genetic parameters for RFI together with growth, carcass, and meat quality traits, and N and P excretion during the test period (35 to 110 kg BW). The RFI explained 20.1% in PP, 26.5% in LWS, 27.6% in LWD, and 29.5% in LR of the phenotypic variability of ADFI. The PP breed differed from the others in this respect, probably due to a lower impact of the variation of body composition on ADFI. Heritability estimates of RFI ranged from 0.21 ± 0.03 (LWD) to 0.33 ± 0.06 (PP) depending on the breed. Heritabilities of N and P excretion traits ranged from 0.29 ± 0.06 to 0.40 ± 0.06. The RFI showed positive genetic correlations with feed conversion ratio (FCR) and excretion traits, these correlations being greater in the sire breeds (from 0.57 to 0.86) than in the dam breeds (from 0.38 to 0.53). Compared with FCR, RFI had weaker genetic correlations with carcass composition, growth rate, and excretion traits. Estimates of genetic correlations between FCR and excretion traits were very close to 1 for all breeds. Finally, excretion traits were, at the genetic level, correlated positively with ADFI, negatively with growth rate and carcass leanness, whereas the halothane n mutation in PP was shown to reduce N and P excretion levels. To conclude, new selection indexes including RFI can be envisaged to efficiently disentangle the responses to selection on growth rate and body composition from those on feed efficiency, with favorable impacts on N and P excretions, particularly in sire pig breeds. However, the switch from FCR to RFI in selection indexes should not resolve the genetic antagonism between feed efficiency and meat quality. [ABSTRACT FROM AUTHOR]

When a diet deficient in Val with exces-sive Leu is offered to pigs, feed intake is reduced. The physiological mechanisms underlying the rejection of branched-chain AA (BCAA) unbalance are unknown. A meal pattern analysis was performed to determine how pigs respond to the ingestion of a diet unbalanced in BCAA to identify the mechanisms responsible for the aversive response of such a diet. Eight female pigs (ini-tial BW of 30.7 ± 1.7 kg at 9 wk of age) received alter-natively a diet either unbalanced in BCAA supply (i.e., a diet deficient in Val with an excess supply of Leu) or a control diet (i.e., a diet with a sufficient supply of Val with an excess supply of Leu) during 4 periods of 5 consecutive days. Feed consumption was monitored continuously to determine feeding behavior. Average daily feed intake of pigs receiving the diet unbalanced in BCAA was 13% less than that in pigs offered the con-trol diet (P < 0.01). Offering the unbalanced diet had no effect on meal size but reduced the number of meals from 9.9 to 8.5 per day (P < 0.01). There was no dif-ference between diets in intermeal interval but a slight trend for an increased meal duration from 14.5 to 16.3 min in pigs receiving the unbalanced diet (P = 0.13). The rejection of feed appeared within the first 2 d after offering the unbalanced diet. The results of this experi-ment indicate that the BCAA unbalanced diet had no effect on satiety and satiation. After initiation of a meal, pigs ate a normal-sized meal and were hungry, but the increase in meal duration and a decrease in the number of meals inferred a negative alliesthesia (less pleasant) response to the BCAA unbalanced diet. On the basis of meal patterns, the rejection of a diet unbalanced in BCAA may not involve short-term mechanisms related to oropharyngeal and gastrointestinal receptors but may be triggered by postabsorptive signals. [ABSTRACT FROM AUTHOR]

Pigs are confronted with changes in farming practices that may affect performance and animal well-being. The sanitary conditions of the farm can have an impact on the ability of pigs to adapt to these changes. This study aimed to analyse how weaned pigs respond to common farming practices of changes in diet and housing in terms of performance, health and behaviour, and how these responses are affected by the sanitary housing conditions, qualified here as good or poor. At weaning at 4 weeks of age, 20 piglets were assigned to 10 blocks of two littermates and each pig within a litter was randomly assigned to one of two sanitary conditions. Pigs were housed individually and received a starter diet. A diet change occurred on day 12 post weaning (starter to weaner diets) and pigs were transferred to the grower unit on day 33 post weaning and continued to receive the weaner diet. From 43 days post weaning, pigs were offered a grower diet and were vaccinated against swine influenza on day 47 and 61 post weaning. On the basis of this design, three post-weaning phases were identified: phase I from day 1 to 11 (post weaning), phase II from day 12 to 32 (after the diet change) and phase III from day 33 to 42 (after the housing change). Individual BW was measured every 3 days, and feed refusals and faecal scores were recorded on a daily basis. Behavioural observations were performed during 28 days by using the instantaneous scan sampling method. Individual blood samples were collected at the end of each phase to analyse the plasma concentration of haptoglobin and on day 68 post weaning to analyse the anti-influenza immunoglobulins G (IgG). Poor sanitary conditions resulted in a decrease in daily gain, feed intake and gain to feed ratio of, respectively, 11%, 5% and 7% (P < 0.05). Pigs in poor sanitary conditions had higher faecal scores (P < 0.05), tended to have higher plasma haptoglobin concentration in phase II (P = 0.06) and had a higher anti-influenza IgG titre (P = 0.11). The diet change affected performance and behavioural responses of pigs in poor but not in good sanitary conditions. Housing change resulted in a 30% decrease in growth and an increase in behaviour oriented towards exploration and excitement. The results of this study show an effect of sanitary conditions on the responses of pigs to a diet change, whereas those to a housing change were little affected by the sanitary conditions. [ABSTRACT FROM PUBLISHER]

Indispensable AA are involved in the control of feed intake. When a diet deficient in Val is offered to pigs, feed intake is typically reduced. This effect is aggravated when dietary Leu is supplied in excess of the requirement. If an unbalanced supply of branched-chain AA (BCAA) is harmful, an anorectic response may serve as a mechanism to prevent this situation. We verified this hypothesis by measuring the voluntary feed intake of a balanced diet offered dur-ing the 30-min period 1 h after ingestion of a test meal deficient or not in Val (Val- and Val+) with an excess of Leu. Twelve and four 6-wk-old crossbred female pigs were used in Exp. 1 and 2, respectively. Prior ingestion of the Val- test meal resulted in a 14% reduction in feed intake compared with that observed after ingestion of the Val+ test meal (P = 0.06) in Exp. 1, indicating that the signal to reduce feed intake occurred within 1 h. It is possible that the plasma concentration of the limiting AA serves as a signal for the dietary AA deficiency. We therefore determined the postprandial plasma concen-trations of BCAA and their a-keto acids after ingestion of Val- and Val+ in 4 pigs in Exp. 2. After ingestion of the Val- diet, plasma concentrations of Val and its keto acid were reduced compared with values observed after ingestion of the Val+ diet. The peak concentration occurred earlier after ingestion of the Val- diet com-pared with that of the Val+ diet. Although the plasma concentration increased after the meal, it declined rap-idly in pigs offered Val-, and the Val concentration 4 h after ingestion of the meal was even less than that observed in the fasted state. In conclusion, it appears that the pig is able to detect a deficient supply of Val within 1 h after ingestion. The plasma concentration of Val or its concentration relative to the other BCAA during the postprandial period may act as a signal indi-cating the AA deficiency. [ABSTRACT FROM AUTHOR]

Experiments carried out to determine the amino acid requirement in growing animals are often based on the premise that the amino acid composition of body protein is constant. However, there are indications that this assumption may not be correct. The objective of this study was to test the effect of feeding piglets a diet deficient or not in total sulfur amino acids (TSAA; Met1Cys) on nitrogen retention and amino acid composition of proteins in different body compartments. Six blocks of three pigs each were used in a combined comparative slaughter and nitrogen balance study. One piglet in each block was slaughtered at 42 days of age, whereas the other piglets received a diet deficient or not in TSAA for 19 days and were slaughtered thereafter. Two diets were formulated to provide either 0.20% Met and 0.45% TSAA (on a standardized ileal digestible basis) or 0.46% Met and 0.70% TSAA. Diets were offered approximately 25% below ad libitum intake. At slaughter, the whole animal was divided into carcass, blood, intestines, liver, and the combined head, tail, feet and other organs (HFTO), which were analyzed for nitrogen and amino acid contents. Samples of the longissimus muscle (LM) were analyzed for myosin heavy chain (MyHC) and actin contents. Nitrogen retention was 20% lower in piglets receiving the TSAA-deficient diet (P<0.01). In these piglets, the nitrogen content in tissue gain was lower in the empty body, carcass, LM and blood (P<0.05) or tended to be lower in HFTO (P<0.10), but was not different in the intestines and liver. The Met content in retained protein was lower in the empty body, LM and blood (P<0.05), and tended to be lower in the carcass (P<0.10). The Cys content was lower in LM, but higher in blood of piglets receiving the TSAA-deficient diet (P<0.05). Skeletal muscle appeared to be affected most by the TSAA deficiency. In LM, the Met content in retained protein was reduced by 12% and total Met retention by more than 60%. The MyHC and actin contents in LM were not affected by the TSAA content of the diet. These results show that a deficient TSAA supply affects the amino acid composition of different body proteins. This questions the use of a constant ideal amino acid profile to express dietary amino acid requirements, but also illustrates the plasticity of the animal to cope with nutritional challenges. [ABSTRACT FROM AUTHOR]

Most studies concerning the Ile requirement in pigs have been carried out using blood products as a protein source, and these have a relatively low Ile content relative to the other branched-chain AA (BCAA). There are indications that an excess supply of one BCAA can affect the utilization of the other BCAA. Little information is available concerning the Ile requirement in pigs when the supply of the other BCAA is moderate (e.g., in cereal-and soybean meal-based diets). The objective of the present study was to evaluate the response of piglets to Ile supplementation under different nutritional conditions. In all experiments, piglets were housed individually and had ad libitum access to feed during a 3-wk period. The first experiment was carried out to study the response of piglets to an increasing Ile supply by using 2 sources of L-Ile differing in degree of purity. Piglets received either a control diet with 48% standardized ileal digestible (SID) Ile:Lys or 1 of 4 other diets containing graded levels of either source of L-Ile to provide 52 or 56% SID Ile:Lys. All diets were formulated to provide 1.00% SID Lys in the diet. Feed intake and growth were not affected by Ile level or Ile source. Experiment 2 was performed to exclude a possible interaction between Ile and Lys supply. In a 2 x 2 factorial arrangement, 2 levels of Lys (1.00 and 1.15% SID Lys) and 2 levels of Ile (48 and 60% SID Ile:Lys) were used. Growth and G:F were 8 and 7% greater in piglets receiving the diet with the greater Lys content, but the Ile:Lys did not affect performance. No interactions were observed between the Lys and Ile supplies. In Exp. 3, a 2 × 2 factorial arrangement was used to test the effect of protein source (spray-dried blood cells or corn gluten meal) and Ile supply (50 or 65% SID Ile:Lys) on performance in piglets. Both protein sources had an elevated BCAA content but differed in Leu and Val contents. Protein source or Ile supply did not affect feed intake, growth, or G:F in the piglets. Plasma concentrations after an overnight fast reflected the difference in AA concentrations of the diets. In conclusion, the results of these experiments indicate that the SID Ile:Lys requirement may be not greater than 50% in piglets receiving cereal- and soybean meal-based diets with a moderate BCAA content. In contrast to other studies, we could not con- firm that the Ile requirement was affected by BCAA content of the diet. [ABSTRACT FROM AUTHOR]

Considerable progress has been made in the nutritional modelling of growth. Most models typically predict (or analyse) the response of a single animal. However, the response to nutrients of a single, representative animal is likely to be different from the response of the herd. To address the variation in response between animals, a stochastic approach towards nutritional modelling is required. In the present study, an analysis method is presented to describe growth and feed intake curves of individual pigs within a population of 192 pigs. This method was developed to allow end-users of InraPorc (a nutritional model predicting and analysing growth in pigs) to easily characterise their animals based on observed data and then use the model to test different scenarios. First, growth and intake data were curve-fitted to characterise individual pigs in terms of BW (Gompertz function of age) and feed intake (power function of BW) by a set of five parameters, having a biological or technico-economical meaning. This information was then used to create a population of virtual pigs in InraPorc, having the same feed intake and growth characteristics as those observed in the population. After determination of the mean lysine (Lys) requirement curve of the population, simulations were carried out for each virtual pig using different feeding strategies (i.e. 1, 2, 3 or 10 diets) and Lys supply (ranging from 70% to 130% of the mean requirement of the population). Because of the phenotypic variation between pigs and the common feeding strategies that were applied to the population, the Lys requirement of each individual pig was not always met. The percentage of pigs for which the Lys requirement was met increased concomitantly with increasing Lys supply, but decreased with increasing number of diets used. Simulated daily gain increased and feed conversion ratio decreased with increasing Lys supply (P < 0.001) according to a curvilinear-plateau relationship. Simulated performance was close to maximum when the Lys supply was 110% of the mean population requirement and did not depend on the number of diets used. At this level of Lys supply, the coefficient of variation of simulated daily gain was minimal and close to 10%, which appears to be a phenotypic characteristic of this population. At lower Lys supplies, simulated performance decreased and variability of daily gain increased with an increasing number of diets (P < 0.001). Knowledge of nutrient requirements becomes more critical when a greater number of diets are used. This study shows the limitations of using a deterministic model to estimate the nutrient requirements of a population of pigs. A stochastic approach can be used provided that relationships between the most relevant model parameters are known. [ABSTRACT FROM AUTHOR]

To reduce the impact of animal production on the environment, the CP content of the diet can be reduced by limiting the excess supply of AA. Improving the balance between AA relative to the requirement of the animal implies that we need to have accurate knowledge of the requirement of individual AA. The purpose of this study was to determine the Val requirement in postweaned piglets (12 to 25 kg) because Val is considered to be potentially limiting to performance after Lys, Met (and Cys), Thr, and Trp. The first experiment was carried out to identify a diet limiting in Lys supply. In this experiment, piglets were offered 1 of 3 diets: a low-CP diet containing low or adequate Lys concentrations [providing 1.0 and 1.2% standardized ileal digestible (SID) Lys, respectively] or a normal-CP diet with 1.2% SID Lys. Average daily gain of piglets receiving the diet containing 1.0% SID Lys was significantly less than that of piglets receiving diets containing 1.2% SID Lys at low or normal CP (486 vs. 522 g/d, respectively; P < 0.01). In Exp. 2, four diets with SID Lys were used in a 2 x 2 factorial design, in which diets contained 57 or 70% SID Val:Lys in combination with 50 or 60% SID Ile:Lys. Independent of the Ile supply, feed intake and daily BW gain were, respectively, 15 and 20% less in piglets receiving diets providing 57% SID Val:Lys compared with piglets receiving 70% SID Val:Lys (P < 0.001). The Tie content of the diet did not affect feed intake or daily BW gain (P > 0.10). Experiment 3 was conducted to evaluate the response of piglets to an increasing Val supply provided by 2 sources of L-Val differing in the degree of purity. Increasing the Val supply from. 58 to 66% SID Val:Lys resulted in a linear increase in both feed intake and daily gain by 24 and 30%, respectively (P < 0.001). No difference was observed between both sources of L-Val (P > 0.10). Experiment 4 was a dose-response study using 5 concentrations of Val supply (ranging from 60 to 80% SID Val:Lys). The estimated SID Val:Lys requirements for maximizing ADFI, ADG, and G:F were, respectively, 74, 70, and 68% using a linear-plateau model, and 81, 75, and 72% using a curvilinear-plateau model. Plasma Val, plasma α-ketoisovaleric acid, Ile, and Leu concentrations after an overnight fast increased with increasing Val supply (P < 0.001). The results of these experiments indicated that the SID Val:Lys was at least 70%, which was slightly greater than the current NRC recommendation. [ABSTRACT FROM AUTHOR]

The impact of dietary fiber on fecal digestion is well-known and provides a comprehensive approach toward nutrient digestibility and availability. Little quantitative information is available on digestion of fiber in the different segments of the gastrointestinal tract (GIT). The objectives of this study were to obtain a method allowing the quantification of the digestive process in different segments of the GIT and to study the impact of dietary fiber on nutrient digestibility. Six barrows (average initial BW of 30 kg and fitted with a simple T-cannula at the proximal duodenum and caudal ileum) were used in a replicated 3 × 3 Latin square design. In each period, pigs were offered 1 of 3 diets differing in fiber content (low, medium, and high). Differences in fiber content were created by replacing wheat and barley with wheat bran. Titanium dioxide was included in the diet as an indigestible marker to determine the apparent digestibility coefficients in different segments of the GIT. The apparent digestibility of ash, CP, DM, and OM increased in the different segments of the GIT. Duodenal digestibility coefficients were negative for ash (e.g., -39.9% for the medium- and high-fiber diets), indicating important endogenous mineral secretions by the stomach and digestive glands. The duodenal digestibility of other nutrients and OM were positive but close to zero and numerically lower in the diets with the greater fiber contents. The fiber content in the diet did not affect the apparent ileal digestibility of nutrients. Increasing the fiber content in the diet affected the fecal digestibility of CP, ether extract, and energy (P < 0.01). The method used for studying sites of digestion in the digestive tract provides promising results, but it is limited due to the high variability that is likely caused by sampling limitations and variation between animals. [ABSTRACT FROM AUTHOR]

An experiment was carried out to evaluate the metabolic utilization of energy in crossbred barrows during feed restriction and subsequent refeeding. Ten pigs, initially weighing 52 kg, were used in 5 blocks of 2 littermates each. A 7-d adaptation period (P1) was used in which pigs were offered feed at 2.60 MJ of ME·kg of BW-0.60·d-1. This adaptation period was followed by a 7-d period (P2), in which 1 pig of each block continued to receive feed at the same level of feeding, whereas for its littermate a 40% reduction in feed intake was imposed (i.e., 1.55 MJ of ME·kg of BW-0.60·d-1). During the subsequent 7-d period (P3), both pigs were offered feed at 2.60 MJ of ME·kg of BW-0.60·d-1. After P3, pigs were fasted for 1 d. Heat production (HP) was measured for all pigs during the last 3 d of P1 and on all days for P2 and P3. Heat production was measured using an open-circuit respiration chamber. Energy and N balances were determined for P1, P2, and P3. The HP was partitioned into HP due to physical activity, the short-term thermic effect of feeding, and resting HP. Feed restriction during P2 decreased (P < 0.01) total HP, resting HP, short-term thermic effect of feeding, and retained energy, whereas HP due to physical activity was not affected by feed restriction (P = 0.50). Likewise, fecal and urinary N loss, protein gain, lipid gain, and ADG were reduced during feed restriction (P < 0.01). There were no differences in components of HP and metabolic utilization of energy between the 2 groups during P1 and P3. Nevertheless, urinary N loss was decreased (P < 0.05) and ADG increased (P < 0.01) during P3 for pigs that were restricted in P2. Compensatory growth after a period of feed restriction does not seem to be related to a change in the metabolic utilization of energy for gain but more likely is due to gain in water and gut contents. [ABSTRACT FROM AUTHOR]

Traditional AA dose-response studies utilize many animals for evaluation of growth performance, and it is hypothesized that a new experimental design based on modern analytical techniques can reduce the number of used animals. The objective was to evaluate a short-term approach with a low number of pigs based on plasma metabolites as a method to determine the dietary Ile, Leu, and Val requirements. Three separate 6 × 6 Latin square experiments having 6 replicates per treatment were conducted with 6 diets containing increasing concentrations of Ile, Leu, and Val which were fed to 6 pigs (BW 8–9 kg) for 2 days, each without a wash-out period for a period of 12 days. The diets were prepared and used in 3 previous traditional-design dose-response studies and had been stored at −20 °C. Blood samples were collected at the end of each 2-day period, and plasma was analyzed for AA and other metabolites using a metabolomics approach. Out of the 18 analyzed plasma AA, 11, 16, and 3 AA for Ile, Leu, or Val, respectively, showed linear or quadratic responses ( P < 0.05) which could be linked to animal growth. The same was found for 4 non-AA metabolites in the Ile, and for 7 non-AA metabolites in the Leu study. 3-Methyl-2-oxovaleric acid, ketohexanoic acid, and α-ketoisovaleric acid were discriminating metabolites for both Ile and Leu. It was possible to fit least squares means of 5, 14, and 2 metabolites in the Ile, Leu, and Val experiments to curvilinear-plateau, broken-line, or quadratic models and thereby estimate an optimum dietary BCAA level. The average optimum BCAA levels across metabolites and models were 0.54 standardized ileal digestible (SID) Ile:Lys, 1.04 SID Leu:Lys, and 0.68 SID Val:Lys which were close to optimums of 0.52, 0.93, and 0.70 found in the previous dose-response studies based on animal growth performance. In conclusion, certain plasma metabolites could be used to estimate Ile, Leu, and Val requirements, and 2 days of adaptation to a new diet was sufficient to reflect relevant biological changes in the blood to different levels of dietary AA in the current study. [ABSTRACT FROM AUTHOR]

Nutritional feed values are currently based on aggregate criteria such as the ileal or faecal digestibility. Digestibility is the result of several processes including hydrolysis, absorption, secretion and passage. In order to develop mechanistic models of digestion to be used for feed evaluation, these processes have to be quantified. The aim of the current study was to determine the enzymatic hydrolysis (or: in vitro digestion) kinetics of main constituents (organic matter, nitrogen and starch) in wheat, barley, wheat bran and soybean meal, using a three-step, enzymatic in vitro method that mimics digestion in the stomach, small and large intestine of pigs. The in vitro results were compared with in vivo results. Hydrolysis kinetics (i.e., solubilisation of feed constituents) was modelled using an exponential segmented model estimating the extent and rate of digestion for each enzymatic digestion step. In vitro digestion of organic matter of soybean meal occurred mainly through the action of pepsin (0.67 versus <0.30 for other feeds, P<0.05), which was caused by the enzymatic digestion of protein at this site. Organic matter of cereals was mainly hydrolysed by enzymes mimicking digestion in the small intestine, and was mainly caused by starch digestion. Fractional in vitro digestion rates of organic matter were higher in the stomach than in the small intestine for cereals (0.20–0.34 min−1versus 0.02–0.15 min−1, P<0.05). The potential in vitro digestibility of organic matter was nearly 0.88 for wheat and soybean meal, 0.79 for barley and 0.61 for wheat bran, which correspond to typical in vivo digestibility values. The in vitro digestibility corresponded reasonably well to in vivo results for enzyme systems mimicking ileal and total tract digestion. The results of this study indicate that it is possible to quantify dynamic aspects of digestion of feedstuffs fed to non-ruminant animals. [Copyright &y& Elsevier]

Abstract: Nutritional feed values are currently based on aggregate criteria such as the ileal or faecal digestibility. Digestibility is the result of two competing processes: digestion and passage. In order to develop mechanistic models of digestion to be used for feed evaluation, both processes have to be quantified. The aim of this study was to determine the hydrolysis kinetics of main constituents (organic matter, N and starch) in wheat, barley, wheat bran and soybean meal, using a three-step, enzymatic in vitro method mimicking digestion in the stomach, small and large intestine of pigs. Kinetics of hydrolysis (i.e. solubilisation of feed constituents) was modelled using an exponential segmented model estimating the extent and rate of digestion in each digestive segment. Digestion of organic matter of soybean meal occurred mainly in the stomach (67% vs. <30% for other feeds) resulting from an efficient protein hydrolysis at this site. Organic matter of cereals was mainly digested in the small intestine (55%), as a result of starch digestion. Fractional digestion rates of organic matter were higher in the stomach than in the small intestine (20–35 vs. 2–15%/min). The potential digestibility of organic matter was nearly 87% for wheat and soybean meal, 78% for barley and 61% for wheat bran, which correspond to typical in vivo digestibility values. The results of the present study allow characterising different feeds with the objective to model the digestion process in pigs. [Copyright &y& Elsevier]

Abstract: Development of mechanistic models of digestion is a means to account for interactions between different nutrients, and between nutrients and the animal. Although some digestion models for pigs have been proposed, quantitative information concerning the underlying processes is extremely limiting. The aim of this study was to determine the effect of dietary fibre on the transit of the solid and liquid phases of digesta in different segments of the gastro-intestinal tract (GIT) in growing pigs. Six barrows (initial BW 30 kg and fitted with two simple T-cannulas at the proximal duodenum and distal ileum) were used in a double 3×3 Latin square design. Pigs were offered diets differing in total dietary fibre content (17, 22 and 27%) at 4 h intervals. A single meal marked with YbO2 and Cr-EDTA was used to determine the passage kinetics of respectively the solid and liquid phases of digesta in different segments of the GIT. The mean retention time (MRT) averaged 1 h from the mouth to the proximal duodenum (stomach), 4 h from the proximal duodenum to the distal ileum (small intestine), and 35 h from the distal ileum to the faecal excretion (large intestine). Increase in dietary fibre content had no effect on MRT in the stomach, tended to decrease MRT of solid phase in the small intestine (P =0.07), and decreased MRT of both phases in the large intestine (43 to 29 h, P =0.06). For all diets, transit of the liquid phase in the large intestine was 4–8 h less than transit of the solid phase. [Copyright &y& Elsevier]