Article

Development of a Dynamic System Simulating Pig Gastric Digestion

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Abstract

The objective of this study was to develop a model for simulating gastric digestion in the pig. The model was constructed to include the chemical and physical changes associated with gastric digestion such as enzyme release, digestion product removal and gastric emptying. Digesta was collected from the stomach cannula of pigs to establish system parameters and to document the ability of the model to simulate gastric digestion. The results showed that the average pH of gastric digesta increased significantly from 2.47 to 4.97 after feed consumption and then decreased 140 min postprandial. The model described the decrease in pH within the pigs’ stomach as pHt = 5.182e-0.0014t, where t represents the postprandial time in minutes. The cumulative distribution function of liquid digesta was Vt = 64.509e0.0109t. The average pepsin activity in the liquid digesta was 317Anson units/mL. There was significant gastric emptying 220 min after feed consumption. The cybernetic dynamic system of gastric digestion was set according to the above data in order to compare with in vivo changes. The time course of crude protein digestion predicted by the model was highly correlated with observed in vivo digestion (r = 0.97; p = 0.0001), Model prediction for protein digestion was higher than that observed for a traditional static in vitro method (r = 0.89; p = 0.0001).

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... It could be presumed to exceed 1 kg considering 3.1~3.5 kg of daily feed intake by finishing pig and slaughter within 4-5 hrs after last meal (Park and Lee, 2011). Nearly 50% of ingested feed remained in pig stomach until 180 mins (Johansen et al, 1996)~220 mins (Chiang et al., 2008) after ingestion. A survey from a local abattoir in Korea reported surprisingly an average of 1.17 kg of USSF from a pig stomach (Son, 2010). ...
... By far, chemical composition or feeding value of USSF have not evaluated in our knowledge. It is certainly meaningful to evaluate the feeding value of USSF (Chiang et al, 2008). Therefore, this study was executed to evaluate the feeding value of USSF in finishing pigs. ...
... Lower energy value of USSF may be explained by a partial digestion of carbohydrate components in the stomach. Nearly 50% of ingested feed remained in pig stomach until 180 mins (Johansen et al., 1996)~220 mins (Chiang et al., 2008) after ingestion. The chemical composition of ingested feeds may be changed due to digestive enzymes (pepsin, salivary amylase, and gastric lipase) in the mouth and stomach (DeRouchey et al., 2009). ...
Article
Insufficient pre-slaughter fasting leaves serious amount of feed-like contents (designated here as un-fasted stomach spent feed, USSF) in the eviscerated pig stomach. This study was intended to evoke economical and environmental seriousness of USSF discharge by estimating its value as pig feed. For finishing pigs feeding trial, three levels (0, 5, and 10%) of USSF were blended with pig feed to prepare control and two treatment diets, respectively. A total of 42 (21 males, 21 females) crossbred (Landrace {\times} Yorkshire {\times} Duroc) finishing pigs weighing 81.5?8.0 kg were employed to 28d feeding trial and in vivo digestibility trial by Cr_2O_3 indicator method with 7 males and 7 female pigs per treatment. In vitro total tract digestion of USSF showed 70.5% and 57.6% of DM and OM digestibilities, respectively which were poorer (p0.05) in dressing percentage and carcass grade among treatments. Results of this study showed that 5% USSF substitution in finishing pigs diet did not exert any disadvantage in terms of production performance and carcass grade. This study implied that un-fasted slaughter causing excessive excretion of USSF should be avoided. If not avoidable, the USSF should not be wasted in abattoir but could be recycled as pig feed.
... The reasons for this disparity may relate to differences between the activity of enzymes and duration of exposure used for in vitro digestion relative to in vivo digestion. Therefore, the objective of this study was to develop a novel in vitro digestion procedure that matched the passage time of diets for growing pigs described by Gao et al. (2018), and mimicked the compositions of simulated gastric, small intestinal and large intestinal fluid of in vivo gastric (Chiang et al., 2008), jejunum (Hu et al., 2010), and cecal (Dang et al., 2018) fluids of growing pigs to accurately predict the DE or ME of unconventional plant protein meals. ...
... The reagent kits including simulated digestive fluid and buffer solution for growing pigs (product number: IVDEGP) were provided by Hunan Zhongben Intelligent Technology Development Co., Ltd. The simulated gastric fluid comprised 890 U/ mL of pepsin hydrochloric acid solution with pH 2.0 (39 C), according to the results of Chiang et al. (2008) and Wang et al. (2019). The gastric buffer contained 80.6 mmol/L of NaCl and 6 mmol/L of KCl, and pH was adjusted to 2.0 at 39 C using 2 mol/L of HCl according to the composition of gastric fluid of pigs described by Fujita et al. (1980). ...
Article
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The objective of this experiment was to develop a new computer-controlled simulated digestion system to predict the digestible energy (DE) and metabolizable energy (ME) of unconventional plant protein meals for growing pigs. Nine meals tested included 1 source of rapeseed meal, 4 sources of cottonseed meal, 2 sources of sunflower meal, and 2 sources of peanut meal. Twenty growing pigs (Duroc × [Landrace × Large White]) with an initial body weight (BW) of 41.7 ± 2.6 kg were allotted to a replicated 10 × 3 incomplete Latin square design to determine the DE and ME of 1 basal diet and 9 experimental diets formulated with 9 unconventional plant protein meals. The DE and ME values of unconventional plant protein meals were calculated by the difference method. The in vitro digestible energy (IVDE) of 1 basal diet, 9 experimental diets, and 9 unconventional plant protein meals were determined with 5 replicates of each sample in a complete randomized arrangement. The IVDE/DE or IVDE/ME ranged from 0.96 to 0.98 or 1.00 to 1.01, and the correlation coefficient between IVDE and DE or ME was 0.97 or 0.98 in 10 experimental diets. Accordingly, the IVDE/DE or IVDE/ME ranged from 0.86 to 1.05 or 0.96 to 1.20, and the correlation coefficient between IVDE and DE or ME was 0.92 or 0.91 in 9 unconventional plant protein meals. The coefficient of variation (CV) of IVDE was less than that of DE and ME in the experimental diets (0.43%, 0.80%, and 0.97% for CV of IVDE, DE and ME, respectively) and unconventional plant protein meals (0.92%, 4.84%, and 6.33% for CV of IVDE, DE and ME, respectively). The regression equations to predict DE from IVDE in 10 experimental diets and 9 unconventional plant protein meals were DE = 0.8851 × IVDE +539 (R2 = 0.9411, residual standard deviation [RSD] = 23 kcal/kg DM, P
... The acidification curve occurring in the gastric compartment was controlled by the software , using the pH data previously reported (Minekus et al., 1995). Porcine pepsin (P-6887, Sigma) was diluted in simulated gastric fluid (SGF) (NaCl 150 mM, adjusted to pH = 6.5) in order to reach 1000 units/mL (Chiang et al., 2008), and added to the gastric compartment at a flow rate of 0.5 mL/min as previously described (Minekus et al., 1995), controlled by the software. Samples were collected at 4, 10, 20, 50, 105, 165, 225, 315 and 405 min of digestion. ...
Article
This study aims to evaluate the impact of heat treatment on the hydrolysis kinetics of cow milk proteins and on the peptide release during in vitro dynamic gastric digestion. SDS-PAGE and ELISA techniques were employed to assess the hydrolysis of proteins over time of digestion. The evolution of the peptidome generated through dynamic digestion of heated and non-heated milk was studied at different times, using MS-based techniques (ion trap and MALDI-TOF/TOF) coupled to liquid chromatography. The peptide homology value between both samples at the end of digestion (48%) confirmed the impact of heat treatment on the identity of peptides generated during digestion, despite their identical initial protein content and being the same matrix in both cases. Heat treatment produced an increased resistance to hydrolysis by pepsin in the casein fraction. However, β-lactoglobulin was found to be more susceptible to hydrolysis. Although differences on the pattern of peptide release were found between both samples, also some common traits after digestion were observed. The regions comprised between the residues 76-93 of β-casein, where several binding epitopes are included, as well as the β-casein domains 126-140 and 190-209 were found to be resistant to pepsin.
... In comparison, human subjects (78 kg mean body weight) fed 1 kg of a complex meal needed 3 to 4 h after the start of the meal to return intra-gastric pH to the initial value (Gardner, Ciociola, & Robinson, 2002), whereas the ratio "meal weight/body weight" was about three times lower than the one used in the current study. Acidification kinetics slows down as meal volume increases in pigs (Chiang, Croom, Chuang, Chiou, & Yu, 2008), as well as in humans (Kalantzi et al., 2006). Despite the overall similarities described above, Fig. 3 also displays strongly different spatial-temporal maps of intra-gastric pH depending on the EWG consumed. ...
Article
The hypothesis is that the characteristics of ingested protein gels influences the subsequent in vivo gastric digestion process. Three egg white gels (EWGs) of identical composition but differing in structure and texture were prepared and fed to pigs. Sampling throughout a 6 h postprandial period, and at different locations in the stomach of the pigs, enabled a detailed spatial-temporal mapping of the pH, dry matter content, particle size and rheological properties. The results showed different gastric acidification kinetics implying an effect of the gel structure and/or texture. The most elastic and cohesive gel resulted in the highest median particle size and the most viscoelastic chyme. Distal and proximal regions of the stomach did not differ in terms of dry matter content, particle size distribution or rheological properties. These results demonstrate the consequences of protein food structure on gastric chyme properties, and thus suggest an effect on the digestion process.
... The dynamic digestive system was set up using parameters taken from the literature ( Table 1). The pH curve in the stomach was obtained by combining data from different in vivo experiments on piglets (Bouzerzour et al., 2012;Chiang, Croom, Chuang, Chiou, & Yu, 2008;Moughan, Cranwell, & Smith, 1991). Gastric pH followed a linear regression pH = À0.011 ...
Article
The best model for studying food digestion remains the Human himself. An alternative to in vivo assays is to use in vitro digestion system. The complexity is to perform a device able to mimic accurately the fate of the food occurring in the human digestive tract. The objective of this work was to develop a simple and rather cheap dynamic digestion system enabling the study of the disintegration occurring in the gastro-intestinal tract of neonate and to validate it towards in vivo data. Digestion of an infant formula was studied both in vitro and in vivo using the piglet model. The formula was adapted to the energy and protein requirements of piglets. Six piglets were slaughtered 30, 90 and 210 min after the meal intake. Effluents from the different compartments of the gut were collected at these 3 time points. In parallel, the same infant formula was digested using the in vitro dynamic digestion system. The device consists in two compartments i.e. stomach and small intestine, and is computer-controlled. Milk proteolysis was followed by SDS-PAGE and ELISA both in vivo and in vitro. The validation was assessed by comparing the kinetics of residual immunoreactivity of β-lactoglobulin and caseins. Results showed a good accordance between the 2 systems of digestion. A level of in vitro/in vivo correlation was established with a correlation coefficient of 0.987. Casein content decreased rapidly during the first 30 minutes of gastric digestion. In contrast, β-lactoglobulin remained much longer intact in the stomach (120 min after ingestion). Intestinal digestion resulted in rapid and drastic hydrolysis, no more intact proteins were detected. This validation on infant formula, using the piglet model, has confirmed that this in vitro dynamic digestion system is reliable.
... The dynamic digestive system was set up using parameters taken from the literature that are listed in Table 8.1. The pH curve in the stomach was obtained by combining data from different in vivo experiments on piglets (Moughan et al. 1991;Chiang et al. 2008;Bouzerzour et al. 2012) whereas intestinal pH was kept constant at 6.5. Other parameters like the transit time of the formula in the stomach (determination of t 1/2 and β) was obtained from an exhaustive review on human infant gastrointestinal physiological conditions (Bourlieu et al. 2014) and fixed at t 1/2 = 70 min or 200 min and β = 1.23 or 2.2 for gastric or intestinal transit time, respectively. ...
Article
Full-text available
A simple two-compartment in vitro dynamic gastrointestinal digestion system allowing the study of the disintegration of food during digestion has been recently developed at INRA. As a first application, it has been used for understanding the mechanisms of infant formula disintegration in the infant gastrointestinal tract. The developed system was validated by comparing the kinetics of proteolysis obtained in vitro towards in vivo data collected on piglets. Results showed a good correlation between in vitro and in vivo data and prove the physiological relevance of the newly developed system.
... The ratio of enzyme to substrate in the hydrolysis and solubilisation of ferulic acid substituted arabinoxylan was much higher than that used in commercial applications. In the animals, the feed flow is dynamic; there is movement and mixing of feed with the contents present in the GI tract where the pH changes as well as digestive enzymes influence both the physical and chemical characteristics of the feed (Chiang et al., 2008). Using microscopy, the contact of the enzyme with the substrate is by diffusion only. ...
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Xylanases in animal feed are primarily utilized to alleviate the antinutritional effects of arabinoxylan, a predominant polymer in cereal cell walls consisting of a β-1,4-xylose polymer, substituted with various sugars. Although xylanases efficiently hydrolyze unsubstituted and substituted arabinoxylans, currently available enzymes are not always able to access highly decorated forms of the polysaccharide, such as arabinoxylans (AX) that contain arabinofuranose substitutions. The highly substituted regions are enriched in both 2- and 3-disubstituted xylose residues. Wheat AX contains very small amounts of 2-monosubstituted xylose residues, whereas barley AXs are characterised by a larger amount of 2-monosubstitution. The structure of rye AX is similar to that of wheat AX, but differences in the abundances of the 2- monosubstituted and 2-and 3- disubstituted xylose residues have been reported. In the current study the efficiency of a monocomponent xylanase was demonstrated on structurally different arabinoxylans present in wheat, rye and barley kernels using microscopic visualization, viscosity and arabinoxylan solubilisation measured as the sum of arabinose and xylose in an analysis of the non-starch polysaccharide (NSP) constituents, as well as xylose alone. Degradation of arabinoxylan components upon exposure to the enzyme was visualized by scanning electron microscopy, autofluorescence and with fluorescence immunocytochemistry and confocal microscopy using commercial antibodies recognizing arabinoxylan in the cereal cell walls. Viscosity data clearly demonstrated effective depolymerisation of arabinoxylans in water extracts from wheat and rye and thereby hydrolytic capacity of the monocomponent enzyme on structurally diverse arabinoxylans. The viscosity reducing effect observed in barley was limited, most likely due to the presence of highly viscous mixed linked ß-D-glucans. Wet chemistry analyses of the complete solubilisation of arabinoxylan (oligomers and polysaccharides) using a standardized xylose assay as well as NSP analyses (measuring polysaccharides, DP > 10) on wheat, rye and barley, provided additional and complementary information to the microscopy conducted on the same cereal samples.
... The interpretation of these subjective measurements to understand the digestive processes is questionable in complex matrices like the intestinal digesta. Digesta flow is dynamic; there is movement and mixing of feed with the contents present in the GIT, and changes in pH and digestive enzyme concentrations influence both the physical and chemical characteristics of the feed (Chiang et al., 2008). Even though the microscopic analysis is more consistent in its findings in in vitro work, where the surrounding materials usually do not interfere with the outcomes (Rosa et al., 2013), the biological relevance of such data is questioned by the present results. ...
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The objective of this study was to evaluate the effect of xylanase supplementation on performance, footpad score (FPS), nutrient digestibility, and intestinal morphometry in broiler chickens. Two-hundred-eighty-eight Ross 308 broiler chicks (one d old) were placed in one of 3 experimental treatments: positive control (PC), negative control (NC) (−150 kcal/kg), and XYL (NC supplemented with xylanase). Each treatment had 8 replicates with 12 animals each. Starter (zero to 21 d) and grower (21 to 42 d) diets, based on wheat and soy-bean meal, were available ad libitum. Body weight gain (BWG) and feed intake were measured, and mortality corrected feed conversion ratio (FCR) was calculated. The relative weights of the empty gastrointestinal tract compartments and FPS were recorded on d 21 and d 42. On d 42, ileal contents were collected for nutrient digestibility determination. Statistical comparisons were performed using one-way ANOVA (JMP Pro 12). The reduction of energy resulted in lighter birds at the end of the study (PC: 2,710 vs. NC: 2,546 g; P = 0.030) whereas xylanase supplementation numerically increased BWG by 84 g (P = 0.229) and improved FCR by 12 points (P = 0.145) compared with the NC. Significant differences in FPS were observed on d 21. Score 0 (no lessions) was predominant in PC and XYL treatments, while score 1 (mild lesions) had a higher frequency in NC birds. Xylanase supplementation numerically increased organic matter (5.9%) and energy (4.7%) utilization with values above those observed with the NC. No treatment effects were observed in any of the morphometric measurements, with the exception of the gizzard (P = 0.036) and the ileum (P = 0.088) on d 42. Xylanase resulted in higher relative gizzard weights compared to NC (P = 0.102). Supplementation of broiler diets with xylanase tended to influence performance, which may be due to a better utilization of nutrients. The increase in gizzard and ileum weights in birds 42 d but not 21 d of age suggests an adaptive response that takes time to develop.
... Yet, pH increases dramatically during a meal, with gastric pH rising to 3 < pH < 5 (Clark et al., 1993;Gardner et al., 2002;Kong and Singh, 2008). This is also true in swine (Chiang et al., 2008). This increase in gastric pH is partially due to the buffering capacity of the meal, and therefore, the extent of the pH rise is dependent on the matrix components of the meal. ...
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Currently, risk assessment of the allergenic potential of novel proteins relies heavily on evaluating protein digestibility under normal conditions based on the theory that allergens are more resistant to gastrointestinal digestion than non-allergens. There is also proposed guidance for expanded in vitro digestibility assay conditions to include vulnerable sub-populations. One of the underlying rationales for the expanded guidance is that current in vitro assays do not accurately replicate the range of physiological conditions. Animal scientists have long sought to predict protein and amino acid digestibility for precision nutrition. Monogastric production animals, especially swine, have gastrointestinal systems similar to humans, and evaluating potential allergen digestibility in this context may be beneficial. Currently, there is no compelling evidence that the mechanisms sometimes postulated to be associated with allergenic sensitization, e.g. antacid modification of stomach pH, are valid among production animals. Furthermore, examples are provided where non-biologically representative assays are better at predicting protein and amino acid digestibility compared with those designed to mimic in vivo conditions. Greater emphasis should be made to align in vitro assessments with in vivo data.
... The ability to survive the oral cavity, the presence of pH 2 to pH 4 in the gastric juice, and bile in the duodenum is a prerequisite for probiotics used as pig feed supplements [13,27]. However, these abilities vary between LAB species and strains, and they involve several mechanisms such as maintaining cell membrane functionality, intracellular pH, and the stability of DNA, RNA and proteins [28][29][30]. ...
Article
Lactic acid bacteria (LAB) play an important role in pig health and performance that arises from their beneficial impacts on the balance of gastrointestinal microbes, ability to fight enteric pathogens, and capacity to support the immune system. The aim of this study was to evaluate the functional and safety aspects of five previously isolated autochthonous LAB strains, (Lactobacillus plantarum 22F, 25F and 31F, Pediococcus acidilactici 72N and Pediococcus pentosaceus 77F) from pig faeces as potential probiotics for a pig feed supplement. The functional and safety properties of the strains were assessed by in vitro tests. The functional properties tested were their abilities in tolerating low pH values under simulated gastric conditions, their cell surface properties (hydrophobicity, auto- and co-aggregation), antibacterial activity against the common enteric pathogenic bacteria in pigs (such as pathogenic Escherichia coli, Salmonella Choleraesuis and Streptococcus suis), and diacetyl production. The safety of the strains was analyzed based on the absent of haemolysis on blood and bile salt hydrolase activity. Although all strains demonstrated diacetyl production, good survivability and antibacterial activities, L. plantarum 22F and 25F showed the best performance with the strongest antibacterial actions against the indicator pathogens. Of the strains, only P. pentosaceus 77F exhibited haemolysis or bile salt hydrolase activity. Furthermore, a principal component analysis revealed that L. plantarum 22F possessed superior functional and safety aspects compared to the other four autochthonous strains and to reference strains L. plantarum JCM 1149 and P. acidilactici DSM 20284. Further in vivo studies using oral administration of the strains are justified to assess their effectiveness as feed supplements for pigs.
... Considering this, our study was focused on the evaluation of the dynamic fluid transport through all simgi ® compartments by a gastrointestinal simulation of an inert compound (resistant to degradation by human gut bacterial enzymes), Cr-EDTA. This type of compound is commonly used to validate the operation of in vitro and in vivo models (Barbé et al., 2013;Chiang et al., 2008). The results of this study showed that the maximum levels of Cr-EDTA in the different simgi ® compartments were reached sequentially along digestion process progression, therefore the compound evidently remains in the system for 48 h, which is compliant with a physiological reality (Aulton and Taylor, 2018). ...
Article
The increasing use of silver nanoparticles (AgNPs) in consumer products has led to concern about their impact on human health. This paper aims to provide new scientific evidence about the modifications and potential effects of AgNPs with food applications during their passage through the digestive tract. For that, two types of AgNPs [solid polyethylene glycol-stabilised silver nanoparticles (PEG-AgNPs 20) and liquid glutathione-stabilised silver nanoparticles (GSH-AgNPs)] were initially subjected to gut-microbial digestion simulation in an in vitro static model. Based on these experiments, digestion of GSH-AgNPs was carried out in a dynamic model (simgi®) that simulated the different regions of the digestive tract (stomach, small intestine and the ascending, transverse and descending colon) in physiological conditions. Dynamic transport of GSH-AgNPs in the simgi® was similar to that observed for the inert compound Cr-EDTA, which discarded any alterations in the intestinal fluid delivery due to the AgNPs. Also, feeding the simgi® with GSH-AgNPs seemed not to induce significant changes in the composition and metabolic activity (i.e., proteolytic activity) of the gut microbiota. Concerning monitoring of AgNps, it was observed that the GSH-AgNPs underwent several transformations in the gastrointestinal fluids and appeared to expose the intestine in ways that were structurally different from the original forms. In compliance with European guidelines, the simgi® model can be considered a useful in vitro tool to evaluate the effects of nanoparticles at the digestive level, prior to human studies, and, therefore, minimising animal testing.
... Several in vitro feed digestibility estimation methods have been developed and can be divided into three groups, that is single-, two-, or three-step models that simulate gastric digestion, gastric/small intestinal digestion, and gastric/small intestinal/large intestinal digestion, respectively [126]. The Boisen and Fernandez [127] in vitro gastric-ileal digestion procedure was been adapted for use in an AD II incubator and it allows for the simultaneous incubation of different pig feedstuffs in sealed polyester bags (5 × 10 cm bags; R510, Ankom Technology, Macedon, NY) in the same incubation vessel [68]. ...
Article
Full-text available
This review summarises the use of the Ankom DaisyII incubator (ADII; Ankom Technology Corporation Fairport, NY, USA), as presented in studies on digestibility, and its extension to other species apart from ruminants, from its introduction until today. This technique has been modified and adapted to allow for different types of investigations to be conducted. Researchers have studied and tested different procedures, and the main sources of variation have been found to be: the inoculum source, sample size, sample preparation, and bag type. In vitro digestibility methods, applied to the ADII incubator, have been reviewed, the precision and accuracy of the method using the ADII incubator have been dealt with, and comparisons with other methods have been made. Moreover, some hypotheses on the possible evolutions of this technology in non-ruminants, including pets, have been described. To date, there are no standardised protocols for the collection, storage, and transportation of rumen fluid or faeces. There is also still a need to standardise the procedures for washing the bags after digestion. Moreover, some performance metrics of the instrument (such as the reliability of the rotation mechanism of the jars) still require improvement.
... Plusieurs modèles du tractus digestif ont été développés pour répondre à des thématiques de nutrition, de toxicologie, de pharmacologie et dans le contexte d'évaluation des risques alimentaires. Il existe deux types de modèles in vitro: les modèles statiques et dynamiques (Blanquet et al., 2004;Chiang et al., 2008;Hoebler et al., 2002;Kong et Singh, 2008aKopf-Bolanz et al., 2012;Kopper et al., 2006;Meunier et al., 2008;Minekus et al., 1995;Savalle et al., 1989;Savoie, 1994;Tharakan et al., 2010;Versantwoort et al., 2004;Yvon et al., 1992) (Hur et al., 2011;Kong et Singh, 2008a;Wickham et al., 2009). Ces modèles in vitro sont paramétrés de telle sorte à reproduire le comportement digestif observé in vivo chez l'être humain ou l'animal. ...
Thesis
L’impact de la structure sur les propriétés biologiques et nutritionnelles des aliments est un sujet d’intérêt récent. La digestion est un processus complexe faisant intervenir plusieurs mécanismes, tels que l’hydrolyse des macronutriments, leur vidange gastrique et leur transit dans l’intestin, la libération de leurs produits d’hydrolyse et l’absorption finale de leurs constituants élémentaires. Tous ces mécanismes sont susceptibles d’être modifiés par la structure de l’aliment ingéré. Le lait est l’un des produits majoritaires de la nutrition humaine et les protéines laitières sont connues pour leur apport en acides aminés essentiels. Le lait peut être transformé et valorisé en de nombreux produits, tels que les yaourts ou les fromages. De plus ces aliments sont très digestibles et apparaissent comme des sources intéressantes de peptides potentiellement bioactifs et d’acides aminés ayant des rôles physiologiques connus. Pour ces raisons, le lait peut être considéré comme un vecteur de bénéfices nutritionnels. Cette étude a ainsi été menée pour comprendre les effets de la structure d’une matrice laitière, modifiée par des procédés technologiques couramment utilisés en industrie, sur les cinétiques de digestion des protéines laitières majeures, les caséines et la β-lactoglobuline. Trois procédés technologiques ont été étudiés, soit seul ou en combinaison : un traitement thermique et une gélification du lait induite par acidification ou par la présure. Six matrices laitières, ayant la même composition mais de structures différentes, ont ainsi été préparées : deux laits écrémés dont l’un natif et l’autre traité thermiquement, les gels présures issus de ces deux laits, et deux gels acides (l’un ferme et l’autre brassé) préparés à partir du lait traité thermiquement. Ces matrices ont ensuite été ingérées par 6 mini-porcs équipés de canules digestives au niveau du duodénum et du jéjunum moyen, ainsi que d’un cathéter artériel. Les effluents digestifs et les plasmas ont alors été prélevés à différents temps sur une période de 7 heures après ingestion. Les concentrations duodénales en chrome (un marqueur de la phase liquide du repas), le contenu en matière sèche, les concentrations résiduelles en protéines, la formation des peptides et les concentrations plasmatiques en acides aminés ont été déterminés sur la période postprandiale. Les caséines et la β-lactoglobuline étaient respectivement sensibles et résistantes à l’hydrolyse dans l’estomac avec les matrices natives, mais leurs cinétiques de digestion étaient au contraire très similaires avec les matrices traitées thermiquement. Les gélifications présure ou acide du lait ont ralenti la vidange gastrique du repas et retardé l’apparition duodénale des protéines et par conséquent, l’absorption des acides aminés, induisant ainsi une diminution de leur biodisponibilité dans le sang. Les gels présures, et plus particulièrement le gel présure non traité thermiquement, ont généré un comportement digestif spécifique, caractérisé par des quantités très faibles de tous les paramètres mesurés au niveau duodénal et dans le sang. Plusieurs hypothèses ont été avancées pour expliquer ce résultat, telle qu’une rétention gastrique très longue associée à des sécrétions digestives prolongées et à une résistance accrue à la protéolyse. Les protéines laitières étaient complètement hydrolysées au niveau jéjunal, quelle que soit la structure de la matrice ingérée. Nous avons ainsi montré que la phase gastrique joue un rôle déterminant dans le contrôle de la biodisponibilité des acides aminés, leur absorption étant en effet fortement liée à la vitesse d’apparition des protéines dans le duodénum. Lorsque nous nous sommes intéressés à la population de peptides libérés dans le duodénum, la structure des matrices laitières n’a pas modifié la localisation des sites de clivage, mais a eu une influence importante sur le nombre de peptides identifiés. Une approche mécanistique de modélisation mathématique a été développée de manière complémentaire aux analyses biologiques. Un modèle à compartiments, basée sur des équations différentielles, a été construit de manière à reproduire les données in vivo en intégrant les processus de vidange et de sécrétions gastriques, de transit intestinal et d’absorption des acides aminés exogènes. Ce modèle était capable de simuler correctement les données expérimentales et d’estimer différents paramètres, principalement liés au transit le long du tractus digestif. Les simulations du modèle ont montré que les différences de cinétiques d’absorption des acides aminés étaient étroitement liées au comportement des matrices laitières dans l’estomac. Ce modèle offre des perspectives intéressantes pour l’intégration de paramètres décrivant la structure des aliments, et plus spécifiquement des produits laitiers, dans un but de prédiction de la biodisponibilité en fonction de la structure de l’aliment ingéré. Les approches in vivo et in silico menées en interaction dans ce projet ont ainsi mis en évidence le rôle majeur de la matrice alimentaire dans la biodisponibilité des nutriments. Cette étude suggère par ailleurs de considérer la modulation de la structure des aliments comme un outil de régulation lors de stratégies nutritionnelles ciblées, notamment pour des populations spécifiques (personnes âgées, en surpoids…).
... The DIDGI's parameters were based on a review of the literature on digestion in humans and pigs. Secretion rates and volumes and the nature and quantity of enzymes in the DIDGI's various compartments were based on previous in vivo studies , Bouzerzour et al., 2012.The pH curve in the stomach was obtained by combining data from in vivo studies in humans and in piglets (Calbet et al. 2004Chiang et al., 2008, Moughan et al., 1991. For the experiments with culture broth alone, the pH in the gastric compartment was defined as −0.063 x t + 6.5 until it reached pH 2. The latter value was then maintained until the end of the experiment. ...
Thesis
Worldwide, the Food Industry uses a broad range of microorganisms while making fermented products, like cheese, most of microorganisms being alive when the food is consumed. Our work aimed at studying the digestive stress response of the surface-ripened cheese microflora and at characterizing their potential immunomodulative properties. In the first part of this work, we investigated the resistance to digestive stress of a selection of 35 microorganisms (bacteria, yeasts and one fungus). We designed a three-step in vitro digestive batch experiment mimicking stresses encountered in (i) the stomach, (ii) the duodenum, (iii) the stomach followed by the duodenum. Alongside, we determined in vitro the microorganisms immunomodulating properties using PBMCs. Batch stress experiments results showed a strong resistance of yeasts to both gastric and duodenal stresses. Bacteria results were more contrasted. PBMCs profiles showed an overall antiinflammatory response for yeasts (with the exception of one species) while bacteria profiles were fairly different, with both pro- and anti-inflammatory profiles among the same species. The second part of the work consisted in developing a Dynamic Gastro-Intestinal Digestive system (DIDGI) and to experiment on a reduced selection of microorganisms and to assess the influence of the growth under real ripening conditions on the ability of microorganisms to withstand digestive stress. Alongside, we tracked the microorganisms’ ability to survive the mouse digestive tract. Some microorganisms grown in cheeses showed fairly different responses during DIDGI experiments compared to lab-cultured microorganisms. A significant part of microorganisms was able to survive the digestive tract of mice. The third part of the work dealt with the microbial ecosystems' influence on the host's immune responses by (i) designing experimental smear-ripened cheeses with mix of microorganisms that had rather pro- or rather antiinflammatory immunomodulatory profils and (ii) fed the ripened cheeses to mice with standardized microbiota. The effect of cheeses consumption on two different models of acute colitis was investigated. Results showed that both cheeses tend to exacerbate the symptoms in one of the colitis model and that the “pro-inflammatory” cheese significantly aggravated the symptoms of the second model of colitis. The fourth and last part of the work consisted in characterizing the molecular response to a similar in vitro batch digestive stress used in the first part of the work. Therefore, we selected a Grampositive bacterium and a Gram-negative bacterium and used RNAseq for transcriptome analysis. A preliminary analysis of the results showed that both organisms were able to up- or downregulate a major part of their metabolism, using both similar mechanisms and specific response per bacterium.
... Three analytical in vitro methods were developed to estimate diet digestibility for swine [29]. The first is a one-step method that mimics gastric digestion. ...
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Undigested neutral detergent fibre (uNDF) is commonly used as an internal marker for the estimation of diet digestibility in ruminants. This work aimed to verify (i) whether the in vivo method with uNDF could be used to evaluate diet digestibility in growing pigs, and (ii) whether pre-treating the samples with neutral detergent solution (NDS) and α-amylase improves the accuracy of the estimates. Samples from a previously published work of two diets with known in vivo digestibility values estimated by the total faecal collection method and 16 individual samples of faeces were used. For each sample, four Ankom F57 bags were weighed. Before the incubation, two F57 bags were pre-treated with NDS and α-amylase. All the samples were incubated for 240 h in the Ankom DaisyII incubator and then analysed for their uNDF contents. Dry matter, organic matter, and neutral detergent fibre digestibilities were estimated using the uNDF contents, and the results were compared with those of the former study. The digestibility values obtained using the uNDF method with pre-treatment were not statistically different from those determined with the total faecal collection. On the contrary, the uNDF method without the pre-treatment could not satisfactorily predict the digestibilities of pig diets.
... The dynamic digestive system was set up using parameters taken from the literature ( Table 1). The pH curve in the stomach was obtained by combining data from different in vivo experiments on piglets (Bouzerzour et al., 2012;Chiang, Croom, Chuang, Chiou, & Yu, 2008;Moughan, Cranwell, & Smith, 1991). Gastric pH followed a linear regression pH = À0.011 ...
... Nevertheless, none survived at pH 2.0. Therefore, we adjusted to pH 3.0, the stomach pH range of pigs [26][27][28], and found >50% survival. Acid Available at www.veterinaryworld.org/Vol.14/May-2021/11.pdf ...
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Background and aim: Using antimicrobials as a feed additive in swine production is prohibited because it is a major cause of the emergence of antimicrobial-resistant bacteria. Probiotics such as Lactobacillus spp. are an attractive alternative to reduce antimicrobial resistance and promote swine growth. This study aimed to evaluate the in vitro probiotic properties of Lactobacillus isolated from indigenous swine manure. Materials and methods: A total of 30 fecal samples from healthy individual indigenous pigs were collected and isolated on de Man, Rogosa, and Sharpe agar. The preliminary screen identified candidates with antibacterial activity against six pathogens and >50% survival and tolerance to acid (pH 3.0) and 1% bile salt. Isolates that passed the initial screen will be tested for other probiotic properties. Results: Of the 314 isolates from 30 pig manure samples, 17 isolates satisfied all initial conditions for probiotic properties. Each isolate has unique, distinctive properties. Isolates B4, B5, B8, B17, B87, and B144 formed thick biofilms, whereas isolates B5, B8, and 27 adhered well to the intestinal wall and exhibited strong autoaggregation properties. Isolate B4 aggregated with Enterohemorrhagic Escherichia coli and Enteropathogenic E. coli. Tests in pH-adjusted cell-free medium indicated that the antibacterial activity resulted from bacterial acidification rather than bacteriocin formation. Sequence analysis (16S rRNA) revealed 16 of the isolates were Lactobacillus plantarum, and only one isolate was Lactobacillus salivarius. Conclusion: We isolated 17 Lactobacillus from swine manure and demonstrated that their probiotic properties might be useful as a probiotic cocktail for swine feed.
... Although these results are similar to what has been previously reported, it was desired to confirm that the trends that have been shown in buffered solutions are still present during dynamic digestion. In addition, it has been previously suggested by Chiang et al. (2008) that over digestion time pepsin could self-hydrolyze, however this was not observed in the current study, as even after 120 min of gastric digestion, pepsin activity was 2000 U/mL, which was the measured pepsin activity prior to digestion ( Fig. 7 B). ...
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Gastric secretions are crucial for food breakdown during digestion. Changes in intragastric pH due to gastric secretions are influenced by meal properties, such as composition, particle size, structure, buffering capacity, and mixing of the meal with gastric secretions. The use of in vitro digestion models has increased recently, however more physiologically-relevant digestion models are needed to better mimic the gastrointestinal tract. The objective of this study was to examine different gastric secretion conditions using a dynamic in vitro digestion model to understand their impact on intragastric pH and protein digestion. Whey protein dispersions were made at two protein concentrations (10% w/v and 30% w/v) and were subjected to gastric digestion. Gastric secretions were set to be at constant rate (2.75 mL/min) or variable rate (1.5 – 9.0 mL/min; based on the intragastric pH). In digestions of 30% w/v dispersion, the digesta pH after 60 min was high (average 4.3±0.3), resulting in low pepsin activity (5.6±0.1% of the maximum) and protein degree of hydrolysis (0.3±0.0% degree of hydrolysis), compared to digestions of 10% w/v dispersions. After 90 min of digestion, the pepsin activity in digesta of 30% w/v dispersions increased to 56.1±0.2%, mainly due to the decrease in the emptied digesta pH (average 2.7±0.2). Protein concentration and gastric emptying played an important role on intragastric pH. Further work is needed to develop a mechanistic understanding between food initial properties, gastric emptying rate, gastric secretions, pH changes, and nutrient digestibility during digestion to study the impact of hydrocolloid dispersions properties on human health.
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Thirty-six microorganisms (twenty-one bacteria, twelve yeasts and three fungi) were isolated from surface-ripened cheeses and subjected to in vitro digestive stress. The approach mimicked gastric and/or duodenal digestion. Lactobacillus rhamnosus GG, Escherichia coli Nissle 1917 and Saccharomyces boulardii were used as reference strains. We studied the microorganisms grown separately in culture medium and then included (or not) in a rennet gel. The microorganisms' immunomodulatory abilities were also assessed by profiling cytokine induction in human peripheral blood mononuclear cells (PBMCs). The loss of viability was less than 1 log CFU/mL for yeasts under all conditions. In contrast, Gram-negative bacteria survived gastric and/or duodenal stress well but most of the Gram-positive bacteria were more sensitive (especially to gastric stress). Inclusion of sensitive Gram-positive bacteria in rennet gel dramatically improved gastric survival, when compared with a non-included cultured (with a 4 log CFU/mL change in survival). However, the rennet gel did not protect the bacteria against duodenal stress. The PBMC cytokine assay tests showed that the response to yeasts was usually anti-inflammatory, whereas the response to bacteria varied from one strain to another.
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This paper evaluates the bioavailability of allium derivative propyl propane thiosulfonate (PTSO) in the pig gastrointestinal tract by means of an in vitro dynamic gastrointestinal tract simulator system (GITSS). The GITSS is based on a membrane bioreactor comprising a continuous stirred-tank reactor connected in series to a continuous plug-flow tubular reactor. Bioavailability values have been evaluated for different vehiculization strategies, including mere carriers such as polyethylene glycol sorbitan monooleate (a nonionic surfactant also known as Tween 80) and encapsulation matrices (β-cyclodextrin vs. mono- and di-glycerides of edible fatty acids mixed with hydrogenated sunflower oil) and compared with the absorption of free PTSO. The net absorbed amount of PTSO in the GITSS when Tween 80 was used as a carrier was over 3.5 times higher than the one for free PTSO. Neither the encapsulated PTSO in β-cyclodextrin nor by means of mono- and di-glycerides of fatty acids plus a vegetable oil succeeded to improve absorption values for free PTSO. These promising results indicate that Tween 80 provides an interesting and high resistance to the PTSO molecule against the simulated digestive conditions in the stomach, and thus it enables favorably the subsequent absorption process of PTSO along the intestine.
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To elucidate the efficacy of different soy protein sources on piglet??s performance, a total of 280 weaned piglets (Duroc??Yorkshire??Landrace, 23?? d of age, 5.86??.45 kg initial BW) were allotted to 5 treatment diets comprising soybean meal (SBM), soy protein concentrate (SPC), Hamlet protein (HP300), fungal (Aspergillus oryzae) fermented soy protein (FSP-A), and fungal plus bacterial (A. oryzae+Bacillus subtilis) fermented soy protein (FSP-B), respectively. Experimental diets for feeding trial were formulated to contain each soy protein sources at 8% level to corn-whey powder basal diet. There were 14 pigs per pen and 4 pens per treatment. Experimental diets were fed from 0 to 14 d after weaning and then a common commercial diet was fed from 15 to 35 d. Also for ileal digestibility studies, 18 pigs were assigned to 6 dietary treatments as N-free, SBM, SPC, HP300, FSP-A and FSP-B with T-canulation at distal ileum for 6 days. At 14th d of experimental feeding, the ADG was significantly higher (p
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A multicompartmental in vitro model has been described, which simulates the dynamic events occurring within the lumen of the gastrointestinal tract of man and monogastric animals. The accuracy of the model for reproducing in vivo data on gastrointestinal transit, pH, bile salt concentrations and the absorption of glucose was tested. The in vivo conditions simulated in the model were based on studies in healthy human volunteers. Mathematical modelling of gastric and ileal delivery with power exponential equations was used for the computer control of meal transit. The model appeared to reproduce accurately the pre-set data on meal transit, pH and bile salt concentrations in the different gastrointestinal compartments. Glucose absorption from the small intestine was almost complete. This model reproduces very closely the dynamic conditions based on the in vivo situation in monogastric animals and man. Therefore, the model can be an important tool in studying the fate of ingested components (for example, food, microorganisms and medicines) during gastrointestinal transit and, consequently, may contribute to the replacement of studies using laboratory animals.
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Breath hydrogen excretion was measured in eight lactase (EC 3.2.1.108)-deficient volunteers ingesting 18 g lactose in the form of milk, yoghurt and heated yoghurt. Total excess hydrogen excretion (area under curve) was significantly lower after yoghurt and heated yoghurt, than after milk: 103 (SE 29), 191 (SE 32), and 439 (SE 69) respectively (P less than 0.001). The oro-caecal transit time of fermentable components from yoghurt and heated yoghurt (mainly lactose) was longer than that from milk: 165 (SE 17), 206 (SE 19), v. 103 (SE 19) min (P less than 0.01). An intestinal perfusion technique was used in the same subjects after ingestion on two consecutive days of 18 g lactose in yoghurt and heated yoghurt. Significantly less lactose was recovered from the terminal ileum after yoghurt than after heated yoghurt meals: 1740 (SE 260) v. 2825 (SE 461) mg (P less than 0.05), and approximately one-fifth of the lactase activity contained in yoghurt reached the terminal ileum. These findings indicate that more than 90% of the lactose in yoghurt is digested in the small intestine of lactase-deficient subjects and suggest that both the lactase activity contained in the viable starter culture and a slow oro-caecal transit time are responsible for this excellent absorption.
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Effect of maintenance and ad libitum intakes on digesta kinetics was studied with six ruminally fistulated cows and six ruminally fistulated wethers to validate the use of sheep as a model of cattle. Complete diets were made up of ratios of alfalfa:cracked corn and soybean meal of 80:20, 55:45, and 30:70. The rate of passage of Cr-mordanted alfalfa and soybean meal in the reticulorumen was negatively related to percentage of concentrate in the diet in both species at low intakes. Passage values of particulate and liquid markers were faster at high than at low intakes in both species for all diets. Rumen liquid volume increased with intake only in the cows on the low and intermediate concentrate diets. No substantial differences were found in particulate passage values between sheep and cattle. However, liquid passage rates from the rumen and the differentials between liquid and particulate dilution rates were higher in cows than in sheep for all diets at both intakes. These results together with those for digestibility data reported in a previous communication suggest that caution should be exercised when extrapolating results from one species to the other.
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Four pigs fitted with a gastric cannula were fed on a wheat-flour-based diet (WF) and three oat-based diets, consisting mainly of oat flour (OF), rolled oats (RO) or oat bran (OB), for 1 week each. The stomach contents were collected quantitatively daily at 0.5, 1, 2, 3 or 5 h after feeding. The viscosity (mPa.s) of the liquid fraction of stomach contents 1 h after feeding was 1.7 with diet WF, 15 with diet OF, 30 with diet RO and approximately 400 with diet OB. The viscosity and the concentration of beta-glucan in the liquid phase was to some extent determined by the dietary level of beta-glucan in the diet. However, there was a trend towards a lower viscosity after longer exposure to the gastric juices. The correlation between logarithmic values for viscosity and concentration of beta-glucan in the liquid phase of digesta was r 0.45. On centrifugation of digesta there was a higher proportion present in the sediment phase when the pigs were fed on diets with a higher content of soluble dietary fibre (DF), suggesting that the digesta was more coherent. This possibility was supported by the higher water-holding capacity (WHC) of the sediment. Feeding diets with oats containing a higher soluble DF content led to lower recoveries of digesta, PEG 4000 (liquid-phase marker), and the DF components beta-glucan and arabinoxylan in the first hour after feeding. No effect related to the DF content of the diet was seen in the gastric emptying of starch and Cr2O3 (solid-phase marker). In conclusion, soluble DF from oats increased the viscosity of stomach contents and increased the ability of the dry matter to retain water. Higher levels of soluble DF led to higher recoveries of digesta, the liquid phase and DF itself in the initial stage of gastric emptying, whereas no effect was seen on the gastric emptying of starch.
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A new method for determining a small amount of polyethyleneglycol (mol. wt. about 4, 000) in feces or ingesta was described. The rates of flow and excretion along the swine digestive tract were compared between polyethyleneglycol and chromic oxide used as an indicator for digestion studies. The former was removed from stomach more rapidly than the latter, and would be delayed in its passage along large intestine owing to absorption of water therein. There was a general agreement between the excretion variations of both indicators. Recoveries during feces collection periods were lower for polyethyleneglycol than for chromic oxide. However, there was no essential difference between both indicators in retention time in the digestive tract, calculated following the idea of Castle. © 1966, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.
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A new method for determining a small amount of polyethyleneglycol (mol. wt. about 4,000) in feces or ingesta was described. The rates of flow and excretion along the swine digestive tract were compared between polyethyleneglycol and chromic oxide used as an indicator for digestion studies. The former was removed from stomach more rapidly than the latter, and would be delayed in its passage along large intestine owing to absorption of water therein. There was a general agreement between the excretion variations of both indicators. Recoveries during feces collection periods were lower for polyethyleneglycol than for chromic oxide. However, there was no essential difference between both indicators in retention time in the digestive tract, calculated following the idea of Castle.
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The use of a two-step in-vitro method to predict the in-vivo ileal digestibility of proteins in pigs was investigated. It proved not possible to predict accurately the ileal protein digestibility with the in-vitro method. By dividing the samples into groups of closely related products, a good relationship (r2 = 0.93) between in-vivo and in-vitro data was only obtained for wheat products, where only five samples were analysed. For beans, peas, rapeseed products and soya bean products it was still not possible to predict the in-vivo protein digestibility (r2 = 0.03-0.60). The in vivo-in vitro relationship was mainly determined by the properties of the proteins and the presence of antinutritional factors, such as lectins and trypsin inhibitors. The first influences both the in-vitro and in-vivo protein degradability and the latter only reduces the in-vivo degradability by stimulating the secretion of endogenous protein. It is suggested that, with the in-vitro method, real ileal digestibility of proteins is predicted. The apparent ileal protein digestibility can only be predicted with the in-vitro method after making corrections for the influence of these antinutritional factors on the secretion of endogenous protein. Possibly corrections are also needed for microbial protein, and protein which is solubilised in the small intestine but not absorbed because of the physical state of the chyme.
A trial was conducted to evaluate the level of wheat substituted for corn in a traditional corn-soy diet and the xylanase supplementation effect on the growth performance and nutrient digestion of broiler chickens. This experiment was a randomized design with a 42 factorial arrangement with four levels of wheat substitution and two levels of enzyme inclusion in the diet. Wheat replaced 0, 25, 50 or 100% corn with or without 1 g/kg xylanase supplementation in iso-nitrogenous and iso-calorific experimental diets. The results showed that in the growing period, broilers attained the highest (p
An in vitro and a feeding trial were conducted to investigate the effect of xylanase supplementation on the feeding value of growing pig diets containing high proportions of Chinese double-low rapeseed meals (DLRM). Seven diets were formulated to meet NRC (1998) nutrient requirements. Diet 1 based on corn-soybean meal was used as positive control 1, and diet 2, a practical diet which incorporated a conventional level of Chinese DLRM (60 g/kg diet), as positive control 2. Diet 3 contained a higher level of DLRM (100 g/kg diet) as the negative control. Diet 3 plus xylanase at 0.10, 0.25, 0.50 and 0.70 g/kg diet created diets 4, 5, 6 and 7, respectively. The seven diets were incubated in triplicate with the in vitro two-stage enzyme incubation method to predict responses of diets to xylanase in terms of digestibility of dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF). In vitro, the negative control had the lowest CP and NDF digestibility. Both DM and CP digestibility were increased (p0.90, p
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An in vitro method for the prediction of protein and amino acid digestibility at ileal level is described. Values of in vitro digestibility of protein in 15 common feedstuffs were all higher than corresponding values of apparent ileal digestibility. The difference is suggested to correspond to endogenous protein losses (EPL). A close relationship between EPL and in vitro undigested dry matter (UDM) was demonstrated: EPL, g kg−1 DM intake = 13.2 + 0.066 × UDM, g kg−1 DM (n = 15;r2 = 0.61; RSD = 4.5; CV = 17.1). The prediction of apparent ileal digestibility of protein (pdNileal) by using the equation: pdNileal, %=dNin vitro, % − 100 × (13.2+0.066×UDM, g kg−1 DM)/Proteinfeed, g kg−1 DM, was highly related to the in vivo determined ileal digestibility of protein (r2 = 0.92; RSD = 3.5; CV = 4.9) in the same 15 feedstuffs. The method was validated with 48 feed mixtures with known in vivo digestibility. The relationship was considerably lower (r2 = 0.57), which was partly due to the narrow variation range in protein digestibility in vivo. The in vitro digestibility of amino acids (measured in nine feedstuffs) was in general closely related to that of protein. Exceptions were cystine, arginine, aspartic acid, glutamic acid and proline. The endogenous losses of the individual amino acids were calculated in a similar way as described for EPL. The resulting amino acid composition of the endogenous protein was very close to reported values in the literature based on direct measurements in vivo. Apparent ileal digestibility of the individual amino acids was predicted in a similar way as described for protein. The relationship was generally higher for essential amino acids, and generally lower for non-essential amino acids, than for protein (e.g. r2 values of 0.65, 0.71 and 0.77 was obtained for lysine, leucine and isoleucine, respectively, but 0.34 and 0.14 for glutamic acid and proline, respectively). The described in vitro approach for protein evaluation seems to have a significant potential for practical purposes.
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We have shown previously that sorghum is highly digestible in the rat. However, other workers have shown that sorghum is much less digestible than wheat, maize, and rice in young children. Because the rat does not show these digestibility differences, we developed an empirical pepsin digestion method, first reported in 1981, which simulates the digestion values found in children. In this report the method has been improved and used to analyze wheat, maize, rice, millet, and sorghum and certain processed samples of millet and sorghum. The pepsin digestion values parallel those found in children for wheat, maize, rice, and sorghum. In addition, a processed sorghum product that gave a high digestion value in children also gave a high value with the in vitro pepsin method.
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A rapid and accurate atomic absorption method for the determination of chromium in faeces samples from pasture experiments using chromic oxide ‘markers’ is described. Of the elements present after ashing and digesting the samples in a phosphoric acid—manganese sulphate—potassium bromate solution silicate, aluminium, calcium and magnesium were found to interfere in the determination. The effects of these interferences were overcome by the addition of calcium to the test solution and by the addition of silicate to the standards, which were prepared in ‘blank’ solutions. The sensitivities of a number of alternate chromium resonance lines relative to that of Cr 3578·7 Å. are given. These lines may be used to increase the concentration range of the analysis. The results of a comparison of the atomic absorption method with a chemical method are given.
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On the basis of in vivo data obtained during digestion of milk proteins in preruminant calf stomach, an in vitro method is proposed to simulate the gastric emptying of digestive products. The reaction vessel, containing 500 mL of skim milk and liquid calf rennet, was placed in a shaken water bath. Peristaltic pumps continuously provided, at a variable flow rate, additional rennet and HCl and allowed the collection of digested products. Evacuated material was collected in trichloroacetic acid at a final concentration of 12%. The pH of the incubation medium was measured during digestion, and the effluents were analyzed for nitrogen content by the Kjeldahl method, liberation of milk proteins by electrophoresis, and some characteristic peptides by HPLC. The model provided in vitro results that showed an excellent correlation with in vivo data.
Article
Our previously proposed in vitro model simulating gastric digestion of proteins was automated. Milk digestion products obtained with this automated ''artificial stomach'' were then compared to results obtained in vivo with preruminant calves. By manipulating four essential parameters, emptying rate of fresh matter, pH decrease, nature of enzyme, and enzyme/substrate ratio, the kinetics of gastric emptying of digestive products observed for 6 h in vivo was quantitatively and qualitatively reproduced in vitro in half the time. Therefore, our model could have a great number of applications in the field of human and animal nutrition, particularly in testing the effect of different processing and preparation procedures on the digestion of food.
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An in-vitro method using commercially available enzymes for the prediction of the in-vivo digestible crude protein content was developed and tested on seven feedstuffs and 16 diets for pigs. Fat-extracted feed samples were consecutively incubated with pepsin at pH 1 and pancreatin at pH 6.8. From the nitrogen content of the feed sample and of the residue after incubation the in-vitro digestibility of the crude protein was calculated. Using the linear regression of in-vitro on in-vivo digestible crude protein of samples obtained in feeding trials, the in-vivo digestible crude protein content (DXPp) in g kg−1 dry matter could be predicted. For feedstuffs and diets the correlation was 0.99 and 0.95 and the residual standard deviation 17 and 6 g kg−1 dry matter, respectively. In a similar procedure the nitrogen solubilised during incubation with enzymes was analysed. The regression value was similar to that of the original procedure. However, this procedure was abandoned because it was more laborious.
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Using an in vitro procedure, with both plant (gluten and edestin) and animal proteins (egg white and casein) as ratio of protein substrate to enzymes (pepsin, trypsin, erepsin) was increased in progressive stages, there was a change in the amino acids released; the proportions of some amino acids progressively increased, others progressively decreased while still others remained constant. The pattern of amino acids released was distinct for each protein and as substrate increased relative to enzymes, certain amino acids essential for the human increased with some proteins and decreased with others which suggests nutritional implications. The variations in amino acids released with changes in ratio of substrate to enzymes was not a random effect but an apparent orderly process. The phenomenon is termed "variable ratio effect".
Article
1. A new in vitro method using the intestinal fluid of the pig for predicting the digestibility of diets was proposed. 2. A 0.5 g sample of pig diet was placed in a 100 ml Erlenmeyer flask, 20 mg pepsin ( EC 3.4.4.1) in 10 ml 0.75 M-hydrochloric acid was added, and the mixture was incubated for 4 h at 37°. Then, after neutralization with 0.2 M-sodium hydroxide, 10 ml of intestinal fluid was added and incubated for an additional 4 h at 37°. This fluid was obtained from a pig fitted with a simple cannula in the upper jejunum. After the two-stage incubations, the contents of the flask was centrifuged for 10 min at 1250 g and the residue transferred to preweighed filter paper for dry matter (DM) and crude protein (nitrogen × 6.25; CP) determinations. The in vitro DM and CP digestibility was calculated on the basis of the original DM and CP content of the diet respectively. 3. The intestinal fluid could be stored at ∓ 20° for 60 d without losing its activity on DM and CP digestion. 4. A high correlation was found between this in vitro method and the standard in vivo procedures, for seven diets commonly used for growing or adult pigs, when diets were ground to pass through a 1 mm screen for the in vitro experiment, but there was an obvious dissimilarity between the two methods, especially in the case of CP: DM, Y = 1.04 X +0.0806 ( r 0.98, P < 0.001); CP, Y = 1.70 X − 0.6092 ( r 0.98, P < 0.001), where Y and X are in vivo and in vitro digestibility respectively. 5. This method is rapid and reproducible and particularly suited for the evaluation of a large number of samples. Since this method assesses only stomach and small intestinal digestion, it therefore may require further modification when used for diets which include large amounts of crude fibre. Also, depending on the needs of the investigator, the addition of a correction factor for endogenous faecal nitrogen loss may be required.
Article
1. Results were collected from thirty-three published and unpublished studies of gastric emptying. The volumes of the meals ranged from 50 to 1250 ml., and composition varied from pure carbohydrates to ordinary food. 2. From the published composition of the meals, their nutritive density, as kcal/ml. (4-18 KJ/ml.) was computed: it ranged from zero to 2-3 kcal/ml. 3. The volume of each meal, or test meal, delivered to the duodenum in 30 min was determined, assuming that gastric emptying was exponential. 4. The greater the nutritive density of a meal, the less was the volume transferred to the duodenum in 30 min. The original volume of meal given was not a determinant of the rate of emptying (ml./min). 5. The slowing of gastric emptying with a meal of high nutritive density was not sufficient to prevent an increased rate of delivery of energy to the duodenum (nutritive density times volume delivered in unit time) with a meal of high nutritive density. 6. Assuming an appropriate relationship for the interaction of a stimulus (kcal/ml.) and duodenal receptors, it was possible to predict a rate of gastric emptying for each meal, given its nutritive density. Knowing the initial volume of the meal, it was possible to predict the mean half time for its emptying. 7. There were eight sets of anomalous results: in four the volumes of meal given were less than 200 ml.; explanations of the anomalies in the other four results could not be provided. 8. The results are consistent with equal slowing of gastric emptying by the duodenal action of the products of digestion of isocaloric amounts of fat, protein and carbohydrate, for example, 4 g fat or 9 g carbohydrate, both 36 kcal, taking carbohydrate and protein as 4 kcal/g and fat as 9 kcal/g.
Article
1. A technique for measuring gastric emptying in growing pigs by complete removal of digesta through a gastric cannula is described. 2. Four pigs were fitted with gastric cannulas and each was used in three trials. 3. The effects of level of feeding (trial 1), cellulose (C), maize-oil (MO) or sucrose (SU) supplementation (trial 2) and the level of water intake (trial 3) on gastric emptying of digesta, dry matter (DM) and nitrogen from a barley-weatings-soya-bean (B) diet were measured during 4 h after the morning feed. 4. In trial 1, pigs were given 0.66, 0.83, 1. 00 or 1. 17 times their standard level of feeding. As the level of feeding rose, so the weight of digesta, DM and N emptied in the first hour after feeding increased. This trend continued to some extent in the second hour, but no effects of level of feeding were seen in the third and fourth hours. 5. In trial 2, maize-oil addition to the diet significantly reduced the gastric-emptying rate of DM in the second hour after feeding, compared with the rates for diet C. The rate of N emptying was significantly slower for diets MO and SU than for diet C. 6. In trial 3 there were no significant effects of water intake level (1. 75, 2. 50 and 3. 25 times the weight of diet) on the rate of DM or N emptying from the stomach. The rate of digesta (and thus of water) emptying in the first hour after feeding increased significantly as the water intake rose. 7. It was concluded that because the pattern of gastric emptying was very similar despite large differences in nutritional inputs, an important property of the process appeared to be resilience.
Article
Gastric emptying was measured in 50 young healthy subjects by means of sequential scintigraphy with two radioactive markers. Gastric emptying of the solid component of the meal was slower than that of the liquid component, corresponding to a linear model (T 1/2, 112 min). Gastric emptying of the liquid component was different, following an exponential model, although only after 45 min (100% of the liquid marker retained in the stomach after 15 min, 56.7% after 45 min, 43.3% after 75 min, and 35.5% after 105 min). Significant differences were found in gastric emptying of both solids and liquids among sexes; women emptied the stomach more slowly than men regardless of age, weight, height, or body surface. A relationship was found between gastric emptying and the phase of the menstrual cycle. Furthermore, a quicker emptying of the liquid component was observed in smokers. These factors should be considered in the evaluation of gastric emptying studies.
Article
A pepsin pancreatin digest index was devised for a rapid, accurate estimation of protein quality. The index was calculated from the amino acids released by an in vitro digestion with pepsin followed by pancreatin. The amino acids were determined by automatic amino acid analysis which allowed rapid protein quality evaluations with very small samples. Using whole egg as a standard, excellent correlation was observed between the pepsin pancreatin index values for 12 proteins and their biological values reported in the literature from feeding trials. The proteins tested were selected to cover a wide range of protein quality. The pepsin pancreatin digest index values showed better correlation with the biological values for the growing rat than did the essential amino acid index which tended to overestimate the value, or the chemical score which tended to underestimate it.
Article
We have shown previously that sorghum is highly digestible in the rat. However, other workers have shown that sorghum is much less digestible than wheat, maize, and rice in young children. Because the rat does not show these digestibility differences, we developed an empirical pepsin digestion method, first reported in 1981, which simulates the digestion values found in children. In this report the method has been improved and used to analyze wheat, maize, rice, millet, and sorghum and certain processed samples of millet and sorghum. The pepsin digestion values parallel those found in children for wheat, maize, rice, and sorghum. In addition, a processed sorghum product that gave a high digestion value in children also gave a high value with the in vitro pepsin method.
Article
A new immobilizing protocol using whey protein isolates was developed to entrap recombinant Saccharomyces cerevisiae. The model yeast strain expresses the heterologous P45073A1 that converts trans-cinnamic acid into p-coumaric acid. Beads resulted from a cold-induced gelation of a whey protein solution (10%) containing yeasts (7.5 x 10(7)cells ml(-1)) into 0.1M CaCl(2). The viability and growth capability of yeasts were not altered by our entrapment process. The release and activity of immobilized yeasts were studied in simulated human gastric conditions. During the first 60 min of digestion, 2.2+/-0.9% (n=3) of initial entrapped yeasts were recovered in the gastric medium suggesting that beads should cross the gastric barrier in human. The P45073A1 activity of entrapped yeasts remained significantly higher (p<0.05) than that of free ones throughout digestion (trans-cinnamic acid conversion rate of 63.4+/-1.6% versus 51.5+/-1.8% (n=3) at 120 min). The protein matrix seemed to create a microenvironment favoring the activity of yeasts in the stringent gastric conditions. These results open up new opportunities for the development of drug delivery system using recombinant yeasts entrapped in whey protein beads. The main potential medical applications include biodetoxication or the correction of digestive enzyme deficiencies.
SAS Users' guide: Statistics, Ver. 8.0
  • Sas
SAS. 1999. SAS Users' guide: Statistics, Ver. 8.0. SAS Institude Inc., Cary, NC.
Effects of varying content of soluble dietary fiber from wheat flour and oat milling fractions on gastric emptying in pigs
  • H N Johansen
  • K E Bach Knudsen
  • B Dandström
  • F Skjoth