The health benefits of breast-feeding have been recognised for a long time. In particular, breast-feeding is associated with lower incidence of necrotising enterocolitis and diarrhoea during the early period of life and with lower incidence of inflammatory bowel diseases, type 2 diabetes and obesity later in life. The higher nutritional and protective degree of human milk is related to its nutritional composition that changes over the lactation period and to the biological activities of specific components while lower growth rate of breast-fed infants may be attributed to their self-regulation of milk intake at a lower level than formula-fed infants. Many results now suggest that the developmental changes in intestinal and pancreatic function that occur postnatally are modulated by the diet. Indeed, formula-feeding induces intestinal hypertrophy and accelerates maturation of hydrolysis capacities; it increases intestinal permeability and bacterial translocation, but does not induce evident differences in microbiota composition. Whether these changes would be beneficial for enhancing absorptive capacities and for educating the gut-associated immune system remains to be further studied. Moreover, it is evident that formula-feeding increases basal blood glucose and decreases plasma ketone body concentrations, while discrepancies on postprandial glycaemia, insulin and incretin responses in both human studies and experimental studies are inconclusive. Manipulating the composition of formula, by reducing protein content, adding prebiotics, growth factors or secretory IgA can modulate intestinal and pancreatic function development, and thereby may reduce the differential responses between breast-fed and formula-fed neonates. However, the developmental responses of the digestive tract to different feeding strategies must be elucidated in terms of sensitivity to developing diseases, taking into account the major role of the intestinal microbiota.

This study investigated intestinal physiology of piglets at weaning. Piglets (n = 60) weaned at 21 d were food deprived for 2 d and then tube-fed using 2 different diets (a conventional diet vs. a wheat-enriched diet). They were slaughtered at d 0, 2, 5, 8, or 15 postweaning. Jejunum, ileum, and colon were mounted in Ussing chambers. In addition, segments of the proximal jejunum of 4 growing pigs were studied 35 d after weaning. Secretory function was assessed by basal short-circuit current (Isc) and secretagogue-stimulated Isc. Glucose absorption was measured by the increase in Isc after the addition of glucose. Epithelial barrier function was measured by transmucosal resistance (R) and horseradish peroxidase (HRP) fluxes across the epithelium. There were no significant differences between the pigs fed the 2 diets for any of the parameters studied. As already reported, a transient villous atrophy was observed. At the same time, we observed an increased basal Isc in jejunum and colon, increased glucose absorption and a dramatic drop of R in jejunum. These parameters had returned to preweaning values by d 5. Weaning was also followed by long-lasting modifications. In jejunum, responses to the secretagogues and glucose absorption were decreased at wk 2 after weaning and were not different between d 15 and 35. Ileal transmucosal resistance increased on d 5 and was stable thereafter. HRP flux in jejunum declined on d 2 and stayed at this low level throughout the experiment. We conclude that weaning induces transient dramatic changes in intestinal physiology but is also a period of maturation of the intestine.

Animal Research, formerly Annales de Zootechnie, publishes original articles, reviews, notes and symposium proceedings concerning research on farm animals

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.

Early-life microbial exposure is of particular importance to growth, immune system development and long-lasting health. Hence, early microbiota composition is a promising predictive biomarker for health and disease but still remains poorly characterized in regards to susceptibility to diarrhoea. In the present study, we aimed to assess if gut bacterial community diversity and composition during the suckling period were associated with differences in susceptibility of pigs to post-weaning diarrhoea. Twenty piglets from 5 sows (4 piglets / litter) were weaned in poor housing conditions to challenge their susceptibility to post-weaning diarrhoea. Two weeks after weaning, 13 pigs exhibited liquid faeces during 2 or 3 days and were defined as diarrhoeic (D) pigs. The other 7 pigs did not have diarrhea during the whole post-weaning experimental periodand were defined as healthy (H) pigs. Using a molecular characterisation of fecal microbiota with CE-SSCP fingerprint, Next Generation Sequencing and qPCR, we show that D and H pigs were mainly discriminated as early as postnatal day (PND) 7, i.e. 4 weeks before post-weaning diarrhoea occurence. At PND 7 H pigs displayed a lower evenness and a higher abundance of Prevotellaceae, Lachnospiraceae, Ruminocacaceae and Lactobacillaceae compared to D pigs. The sPLS regression method indicates that these bacterial families were strongly correlated to a higher Bacteroidetes abundance observed in PND 30 H pigs one week before diarrhoea. These results emphasize the potential of early microbiota diversity and composition as being an indicator of susceptibility to post-weaning diarrhoea. Furthermore, they support the health promoting strategies of pig herds through gut microbiota engineering.

We analysed the spatio-temporal sequence of events concerning the morphology, physiology and ecology of the gut of piglets during the 2 weeks following weaning, in order to provide a limited number of variables that could be relevant markers of the gut post-weaning changes. An experiment was conducted on sixty piglets fasted for 2 d, then administered a weaning diet with a moderate or a high content of wheat using controlled gastric feeding, and slaughtered at different time-points post-weaning. Sixty-nine variables were analysed by principal component analysis. The results showed that the temporal changes induced in the gut by weaning can be divided into two periods: an acute period happening immediately after weaning, followed after day 5 by a more progressive adaptative and maturational phase. The main factors of this adaptation were the refeeding process and the time, while the dietper sehad little influence. The villus length, lactase activity, macromolecule fluxes across the jejunum and the plasma cholecystokinin were proposed as markers of the acute phase. The mass of the jejunum, the weight of the pancreas, the content of stomach, the trypsin activity and the theophylline-induced secretion in jejunum were related to the re-feeding. Markers proposed to follow the gut maturation were the maltase activity, the glucose absorption and the basal resistance in the ileum, the lactobacilli and enterococci in the colon, and the pH of colonic and caecal contents. These markers might be helpful to design suitable diets to limit post-weaning gut disorders in pigs.