S.J. Koopmans

Impact of bioactive substances on the gastrointestinal tract and performance of weaned piglets: a review.

The EU ban on in-feed antibiotics has stimulated research on weaning diets as a way of reducing post-weaning gut disorders and growth check in pigs. Many bioactive components have been investigated but only few have shown to be effective. Amongst these, organic acids (OA) have been shown to exert a bactericidal action mediated by non-dissociated OA, by lowering gastric pH, increasing gut and pancreas enzyme secretion and improving gut wall morphology. It has been postulated that they may also enhance non-specific immune responses and improve disease resistance. In contrast, relatively little attention has been paid to the impact of OA on the stomach but recent data show they can differently affect gastric histology, acid secretion and gastric emptying. Butyrate and precursors of butyric acid have received special attention and although promising results have been obtained, their effects are dependent upon the dose, treatment duration, initial age of piglets, gastrointestinal site and other factors. The amino acids (AA) like glutamine, tryptophan and arginine are supportive in improving digestion, absorption and retention of nutrients by affecting tissue anabolism, stress and (or) immunity. Glutamine, cysteine and threonine are important for maintaining mucin and permeability of intestinal barrier function. Spray-dried plasma (SDP) positively affects gut morphology, inflammation and reduces acquired specific immune responses via specific and a-specific influences of immunoglobulins and other bioactive components. Effects are more pronounced in early-weaned piglets and under poorer health conditions. Little interaction between plasma protein and antibiotics has been found, suggesting distinct modes of action and additive effects. Bovine colostrum may act more or less similarly to SDP. The composition of essential oils is highly variable, depending on environmental and climatic conditions and distillation methods. These oils differ widely in their antimicrobial activity in vitro and some components of weaning diets may decrease their activity. Results in young pigs are highly variable depending upon the product and doses used. These studies suggest that relatively high concentrations of essential oils are needed for beneficial effects to be observed and it has been assumed that these plant extracts mimic most of the effects of antibiotics active on gut physiology, microbiology and immunology. Often, bioactive substances protective to the gut also stimulate feed intake and growth performance. New insights on the effects of selected OA and AA, protein sources (especially SDP, bovine colostrum) and plant extracts with anti-bacterial activities on the gut are reported in this review.

Critical review evaluating the pig as a model for human nutritional physiology

The present review examines the pig as a model for physiological studies in human subjects related to nutrient sensing, appetite regulation, gut barrier function, intestinal microbiota and nutritional neuroscience. The nutrient-sensing mechanisms regarding acids (sour), carbohydrates (sweet), glutamic acid (umami) and fatty acids are conserved between humans and pigs. In contrast, pigs show limited perception of high-intensity sweeteners and NaCl and sense a wider array of amino acids than humans. Differences on bitter taste may reflect the adaptation to ecosystems. In relation to appetite regulation, plasma concentrations of cholecystokinin and glucagon-like peptide-1 are similar in pigs and humans, while peptide YY in pigs is ten to twenty times higher and ghrelin two to five times lower than in humans. Pigs are an excellent model for human studies for vagal nerve function related to the hormonal regulation of food intake. Similarly, the study of gut barrier functions reveals conserved defence mechanisms between the two species particularly in functional permeability. However, human data are scant for some of the defence systems and nutritional programming. The pig model has been valuable for studying the changes in human microbiota following nutritional interventions. In particular, the use of human flora-associated pigs is a useful model for infants, but the long-term stability of the implanted human microbiota in pigs remains to be investigated. The similarity of the pig and human brain anatomy and development is paradigmatic. Brain explorations and therapies described in pig, when compared with available human data, highlight their value in nutritional neuroscience, particularly regarding functional neuroimaging techniques.

Increasing weaning age of piglets from 4 to 7 weeks reduces stress, increases post-weaning feed intake but does not improve intestinal functionality

This study tested the hypothesis that late weaning and the availability of creep feed during the suckling period compared with early weaning, improves feed intake, decreases stress and improves the integrity of the intestinal tract. In this study with 160 piglets of 16 litters, late weaning at 7 weeks of age was compared with early weaning at 4 weeks, with or without creep feeding during the suckling period, on post-weaning feed intake, plasma cortisol (as an indicator of stress) and plasma intestinal fatty acid binding protein (I-FABP; a marker for mild intestinal injury) concentrations, intestinal morphology, intestinal (macro)molecular permeability and intestinal fluid absorption as indicators of small intestinal integrity. Post-weaning feed intake was similar in piglets weaned at 4 weeks and offered creep feed or not, but higher (P < 0.001) in piglets weaned at 7 weeks with a higher (P < 0.05) intake for piglets offered creep feed compared with piglets from whom creep feed was witheld. Plasma cortisol response at the day of weaning was lower in piglets weaned at 7 weeks compared with piglets weaned at 4 weeks, and creep feed did not affect cortisol concentration. Plasma I-FABP concentration was not affected by the age of weaning and creep feeding. Intestinal (macro)molecular permeability was not affected by the age of weaning and creep feeding. Both in uninfected and enterotoxigenic Escherichia coli-infected small intestinal segments net fluid absorption was not affected by the age of weaning or creep feeding. Creep feeding, but not the age of weaning, resulted in higher villi and increased crypt depth. In conclusion, weaning at 7 weeks of age in combination with creep feeding improves post-weaning feed intake and reduces weaning stress but does not improve functional characteristics of the small intestinal mucosa.

Cross-Species Comparison of Genes Related to Nutrient Sensing Mechanisms Expressed along the Intestine

Introduction Intestinal chemosensory receptors and transporters are able to detect food-derived molecules and are involved in the modulation of gut hormone release. Gut hormones play an important role in the regulation of food intake and the control of gastrointestinal functioning. This mechanism is often referred to as “nutrient sensing”. Knowledge of the distribution of chemosensors along the intestinal tract is important to gain insight in nutrient detection and sensing, both pivotal processes for the regulation of food intake. However, most knowledge is derived from rodents, whereas studies in man and pig are limited, and cross-species comparisons are lacking. Aim To characterize and compare intestinal expression patterns of genes related to nutrient sensing in mice, pigs and humans. Methods Mucosal biopsy samples taken at six locations in human intestine (n = 40) were analyzed by qPCR. Intestinal scrapings from 14 locations in pigs (n = 6) and from 10 locations in mice (n = 4) were analyzed by qPCR and microarray, respectively. The gene expression of glucagon, cholecystokinin, peptide YY, glucagon-like peptide-1 receptor, taste receptor T1R3, sodium/glucose cotransporter, peptide transporter-1, GPR120, taste receptor T1R1, GPR119 and GPR93 was investigated. Partial least squares (PLS) modeling was used to compare the intestinal expression pattern between the three species. Results and conclusion The studied genes were found to display specific expression patterns along the intestinal tract. PLS analysis showed a high similarity between human, pig and mouse in the expression of genes related to nutrient sensing in the distal ileum, and between human and pig in the colon. The gene expression pattern was most deviating between the species in the proximal intestine. Our results give new insights in interspecies similarities and provide new leads for translational research and models aiming to modulate food intake processes in man.

Effects of resistant starch on behaviour, satiety-related hormones and metabolites in growing pigs

Resistant starch (RS) has been suggested to prolong satiety in adult pigs. The present study investigated RS-induced changes in behaviour, satiety-related hormones and metabolites in catheterized growing pigs to explore possible underlying mechanisms for RS-induced satiety. In a cross-over design with two 14-day periods, 10 pigs (initial BW: 58 kg) were assigned to two treatments comprising diets containing either 35% pregelatinized starch (PS) or 34% retrograded starch (RS). Diets were isoenergetic on gross energy. Pigs were fed at 2.8× maintenance. Postprandial plasma response of satiety-related hormones and metabolites was measured at the end of each period using frequent blood sampling. Faecal and urinary energy losses were measured at the end of each period. Behaviour was scored 24 h from video recordings using scan sampling. Energy digestibility and metabolizability were ~6% lower in RS compared with PS diet (P<0.001), and metabolizable energy (ME) intake was ~3% lower in RS-fed than in PS-fed pigs (P<0.001). RS-fed pigs showed less feeder-directed (P=0.001) and drinking (P=0.10) behaviours than PS-fed pigs throughout the day. Postprandial peripheral short-chain fatty acid (SCFA) levels were higher in RS-fed than in PS-fed pigs (P<0.001). Postprandial glucose and insulin responses were lower in RS-fed than in PS-fed pigs (P<0.001). Triglyceride levels were higher in RS-fed than in PS-fed pigs (P<0.01), and non-esterified fatty acid levels did not differ between diets (P=0.90). Glucagon-like peptide-1 (GLP-1) levels were lower in RS-fed than in PS-fed pigs (P<0.001), and peptide tyrosine tyrosine (PYY) levels did not differ between diets (P=0.90). Blood serotonin levels were lower (P<0.001), whereas monoamine oxidase activity (P<0.05) and tryptophan (P<0.01) levels were higher in RS-fed than in PS-fed pigs. Despite a lower ME intake, RS seemed to prolong satiety, based on behavioural observations. Possible underlying mechanisms for RS-induced satiety include increased 24 h plasma SCFA levels, and decreased postprandial glucose and insulin responses. GLP-1 and PYY seemed not to play a role in RS-induced satiety. Low blood serotonin levels in RS-fed pigs suggested a difference in intestinal serotonin release between treatments. Increased postprandial plasma triglyceride levels corresponded with increased SCFA levels, but it is unclear whether triglycerides may have signalled satiety in RS-fed pigs.

Physiology, regulation and multifunctional activity of the gut wall: a rationale for multicompartmental modelling.

A rationale is given for a modelling approach to identify the mechanisms involved in the functioning and metabolic activity of tissues in the wall of the gastrointestinal tract. Maintenance and productive functions are discussed and related to the distinct compartments of the gastrointestinal tract and the metabolic costs involved. Functions identified are: tissue turnover; tissue proliferation; ion transport; nutrient transport; secretions of digestive enzymes, mucus and immunoglobulins; production of immune cells. The major nutrients involved include glucose, amino acids and volatile fatty acids. In vivo measurements of net portal fluxes of these nutrients in pigs and ruminants are evaluated to illustrate the complexity of physiology and metabolic activity of the gastrointestinal tract. Experimental evidence indicates that high, but variable and specific, nutrient costs are involved in the functioning of the gastrointestinal tract.

Cholecystokinin regulates satiation independently of the abdominal vagal nerve in a pig model of total subdiaphragmatic vagotomy

The vagal nerve and gut hormones CCK and GLP-1 play important roles in the control of food intake. However, it is not clear to what extent CCK and GLP-1 increase satiation by stimulating receptors located on abdominal vagal nerve endings or via receptors located elsewhere. This study aimed to further explore the relative contribution of the abdominal vagal nerve in mediating the satiating effects of endogenous CCK and GLP-1. Total subdiaphragmatic vagotomy or sham operation was combined with administration of CCK1 and GLP-1 receptor antagonists devazepide and exendin (9-39) in 12 pigs, applying an unbalanced Latin Square within-subject design. Furthermore, effects of vagotomy on preprandial and postprandial acetaminophen absorption, glucose, insulin, GLP-1 and CCK plasma concentrations were investigated. Ad libitum liquid meal intake (mean±SEM) was similar in sham and vagotomized pigs (4180±435 and 3760±810 g/meal). Intake increased by about 20% after blockade of CCK1 receptors, independently of the abdominal vagal nerve. Food intake did not increase after blockade of GLP-1 receptors. Blockade of CCK1 and GLP-1 receptors increased circulating CCK and GLP-1 concentrations in sham pigs only, suggesting the existence of a vagal reflex mechanism in the regulation of plasma CCK1 and GLP-1 concentrations. Vagotomy decreased acetaminophen absorption and changed glucose, insulin, CCK and GLP-1 concentrations indicating a delay in gastric emptying. Our data show that at liquid feeding, satiation is decreased effectively by pharmacological blockade of CCK1 receptors. We conclude that regulation of liquid meal intake appears to be primarily regulated by CCK1 receptors not located on abdominal vagal nerve endings.

Effects of surplus dietary L-tryptophan on stress, immunology, behavior, and nitrogen retention in endotoxemic pigs.

The possible beneficial effects of surplus dietary Trp (+5 g of Trp/kg of diet) on factors related to stress, immunology, behavior, and N retention were investigated in postweaning piglets (approximately 15 kg of BW) challenged for 10 d with intravenous bacterial lipopolysaccharide (from Escherichia coli). Two diets fed restrictively (732 kJ of NE/kg of BW(0.75)/d) were compared, 1) a basal diet (apparent ileal digestible Trp = 1.9 g/kg; the recommended amount of Trp to warrant near-optimal growth in nonendotoxemic piglets), and 2) a Trp-enriched basal diet (+5 g of free l-Trp/kg), with 8 individually housed piglets per diet. Pooled salivary cortisol, but not plasma cortisol sampled at euthanasia, showed a tendency (P = 0.07) toward reduced concentrations in the Trp group (1.1 vs. 1.4 ng/mL; pooled SE = 0.1 ng/mL). Plasma C-reactive protein was reduced (P = 0.04) in the Trp group (0.9 vs. 5.0 mg/L; pooled SE = 1.3 mg/L), but haptoglobin, IL-6, tumor necrosis factor α, and lipopolysaccharide-induced fever were similar between the 2 dietary treatments. Physical activity related to approaching a human showed a tendency (P = 0.08) toward increased latency time in the Trp group (101 vs. 60 s; pooled SE = 16 s), but the times spent standing, sitting, and lying were similar between dietary treatments. The ADFI, ADG (346 vs. 302 g/d; pooled SE = 14 g/d; P = 0.11), body N retention (11.6 vs. 11.0 g/d; pooled SE = 0.2 g/d; P = 0.18), and G:F (0.55 vs. 0.49; pooled SE = 0.03; P = 0.17) were not different between the groups fed Trp and the basal diet. In conclusion, surplus dietary Trp had limited effects on stress, immunology, behavior, and N retention in a pig model of systemic endotoxemia.

The A0 blood group genotype modifies the jejunal glycomic binding pattern profile of piglets early associated with a simple or complex microbiota

The intestinal epithelium glycocalyx sugar motif is an important determinant of the bacterial-host interaction and may be affected in pigs by gut microbiota and by blood group genotype. The aim was to study the effect of intestinal association with different microbiota and A0 blood group genotypes on the expressed glycomic pattern in the small intestine. Twelve caesarean-derived pigs previously associated with a simple association (SA) or complex association (CA) microbiota were selected at 26 to 37 d of age. In each subject, different jejunal loops were perfused for 8 h with enterotoxigenic K88 (ETEC), ETEC fimbriae (F4), (LAM), or a saline control. The piglets were genotyped for A0 blood group and the glycomic profile was evaluated by microscopic screening of lectin binding: peanut agglutinin (PNA), which is galactose specific; agglutinin I (UEA), which is fucose specific; lectin II (MALii), which is sialic acid specific; concavalin A, which is mannose specific; soybean agglutinin (SBA), which is -acetyl-galactosamine specific; and wheat germ agglutinin (WGA), which is -acetyl-glucosamine specific. A0 pigs had fewer UEA-positive cells, MALii-positive cells ( < 0.001), and SBA-positive cells ( < 0.10) than 00 pigs. Simple association pigs had more SBA positive cells ( < 0.01) than CA pigs. Enterotoxigenic K88-perfused intestinal loops had fewer UEA-positive cells ( < 0.01) and WGA positive cells ( < 0.001) cells and more PNA positive cells (only in SA pigs, < 0.01). No effects of introduction of F4 and LAM in the intestinal lumen were observed. The porcine A0 blood group genotype and the luminal presence of ETEC strongly affected the jejunal mucosa glycomic pattern profile whereas an early oral simple or complex microbial association had limited effects. Pig genetic background has relevance on the cross talk between intestinal epithelium glycocalyx sugar motif and ETEC and, ultimately, on the gut microbial colonization in later life.

Molecular networks affected by neonatal microbial colonization in porcine jejunum, luminally perfused with enterotoxigenic Escherichia coli, F4ac fimbria or Lactobacillus amylovorus

The development of an early complex gut microbiota may play an important role in the protection against intestinal dysbiosis later in life. The significance of the developed microbiota for gut barrier functionality upon interaction with pathogenic or beneficial bacteria is largely unknown. The transcriptome of differently perfused jejunal loops of 12 caesarian-derived pigs, neonatally associated with microbiota of different complexity, was studied. Piglets received pasteurized sow colostrum at birth (d0), a starter microbiota (Lactobacillus amylovorus (LAM), Clostridium glycolicum, and Parabacteroides) on d1-d3, and a placebo inoculant (simple association, SA) or an inoculant consisting of sow’s diluted feces (complex association, CA) on d3-d4. On d 26–37, jejunal loops were perfused for 8 h with either enterotoxigenic Escherichia coli F4 (ETEC), purified F4 fimbriae, LAM or saline control (CTRL). Gene expression of each intestinal loop was analyzed by Affymetrix Porcine Gene 1.1_ST array strips. Gene Set Enrichment Analysis was performed on expression values. Compared to CTRL, 184 and 74; 2 and 139; 2 and 48 gene sets, were up- and down-regulated by ETEC, F4 and LAM, respectively. ETEC up-regulated networks related to inflammatory and immune responses, RNA processing, and mitosis. There was a limited overlap in up-regulated gene sets between ETEC and F4 fimbriae. LAM down-regulated genes related to inflammatory and immune responses, as well as to cellular compound metabolism. In CA pigs, 57 gene sets were up-regulated by CA, while 73 were down-regulated compared to SA. CA up-regulated gene sets related to lymphocyte modulation and to cellular defense in all loop perfusions. In CA pigs, compared to SA pigs, genes for chemokine and cytokine activity and for response to external stimuli were down-regulated in ETEC-perfused loops and up-regulated in CTRL. The results highlight the importance of the nature of neonatal microbial colonization in the response to microbial stimuli later in life.