Dietary and microbially derived fatty acids (FA) play important roles in gut mucosal inflammatory signaling, barrier function and oxidative stress response. Nevertheless, little information is available about gastrointestinal FA profiles and receptor distribution in pigs, especially for long-chain FA (LCFA). Therefore, the present pilot study aimed to 1) investigate the gastrointestinal FA profiles; 2) link the luminal FA profiles to the mucosal expression of genes related to FA sensing and signaling; and 3) assess potential dietary effects on gut and systemic lipid metabolism in pigs. Gut, liver and serum samples were obtained from barrows (13.1 ± 2.3 kg) fed diets containing either phytase (500 phytase units/kg diet) or cereals treated with 2.5% lactic acid (LA) (n = 8/diet) for 18 days. Results showed gut regional and diet-related differences in luminal FA profiles and mucosal receptor expression, whereas diet little affected hepatic expression levels and serum lipids. Short-chain fatty acids (SCFA) increased from stomach, jejunum and ileum to the cecum (P < 0.05), whereas LCFA were higher in stomach, cecum and colon than in jejunum and ileum (P < 0.05). LA-treated cereals enhanced cecal acetate and butyrate, whereas phytase and LA treated cereals decreased the LCFA by 35.9 and 14.4%, respectively (P < 0.05). Gut regional differences suggested stronger signaling via FFAR1 expression in the ileum, and via FFAR2, FFAR4 and HCAR1 expression in cecum and colon (P < 0.05). Expression of AMPK, FASN, PPARG, SREBP1 and SREBP2 was higher in the cecum and colon compared to the small intestine (P < 0.05), with stronger sensing via FASN and SREBP2. Phytase decreased expression of FFAR2 and FFAR4, whereas it increased that of FFAR3 and MCT1 in the cecum (P < 0.05). LA-treated cereals raised cecal expression of FFAR3 and HCAR1 (P < 0.05). Pearson’s correlations (|r| > 0.35; P < 0.05) supported that FA receptor- and nuclear transcription factor-dependent pathways were involved in the mucosal regulation of gut incretin expression but differed across gut regions. In conclusion, results support regional differences in SCFA, lactate and LCFA sensing and absorption capacities in the small and large intestines of pigs. Effects of phytase and the LA-treated cereals on intestinal FA levels and signaling can be explained by differences in nutrient flows (e.g. phosphorus and carbohydrate fractions). This overview provides a solid basis for future intestinal FA sensing in pigs.

Phosphorus (P) is an essential nutrient for the gut bacteria and the host. Nevertheless, little information exists to what extent an improved P availability in the small intestine leads to functional adaptations in bacterial metabolic pathways in the large intestine. Therefore, we investigated the changes in the taxonomic and functional bacterial metagenome in cecal digesta of growing pigs fed diets containing phytase and/or cereals treated with 2.5% lactic acid (LA) for 19 days (n=8/diet) using shotgun metagenome sequencing. Especially the phytase supplementation resulted in distinct bacterial communities, affecting almost all major bacterial families, whereas functional changes were less dramatic among feeding groups. While phytase decreased predominant Prevotellaceae, it seemed that Clostridiaceae, Ruminococcaceae and Lachnospiraceae filled the opening metabolic niches (P < 0.05). The LA-treated cereals reduced Bacteroidaceae, while increasing Veillonellaceae but mainly when fed as single treatment (P < 0.05). Associated with the taxonomic alterations, phytase caused changes within the major functional pathways ‘amino acid metabolism’, ‘translation’, ‘membrane transport’, ‘folding, sorting and degradation’ and ‘energy metabolism’, whereas the LA-treatment of cereals decreased enzymatic capacities within ‘carbohydrate metabolism’ and ‘energy metabolism’ (P < 0.05). Metabolic dependencies from ‘starch and sucrose metabolism’, ‘glycolysis/gluconeogenesis’ and ‘citrate cycle’ were indicated by diet-associated changes in enzymatic capacities related to short-chain fatty acid, methane, vitamin and bacterial antigen synthesis. Accordingly, present results support the importance of the intestinal P availability for the bacterial metabolism. However, functional profiles were less different than taxonomic profiles among dietary treatment, indicating a certain metabolic plasticity within the cecal metagenome. IMPORTANCE Dietary strategies (e.g. phytase supplementation and lactic acid-(LA)-treatment of cereals) used to improve the phytate-phosphorus (P) availability from pig feed reduce the amount of P flowing into the large intestine, whereas LA-treatment induced changes in nutrient fractions alter the substrate being available to the microbiota. In ruminants, lower intestinal P availability compromises the fibrolytic activity of the microbiome. Here, we report that the functional capacities were less dramatically affected than the taxonomic composition by phytase and LA-treated cereals. The bacterial community appeared to be partly capable of functionally compensating for the altered flow of P by replacing taxa with higher P needs by those with lower P needs. Therefore, by acting as mucosal immune stimulants, the alterations in microbiota-associated molecular patterns (MAMP) due to the taxonomic shifts may play a greater role for host physiology and health than functional differences caused by varying intestinal P availabilities, which merits further research.

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Host-Toltrazuril-C. suis Interactions diversity on dol 11. In addition to cystoisosporosis prevention, toltrazuril seems to contribute to the stabilization of the gut microbial development during the suckling phase and thus may reduce the need for antibiotics to control infections with secondary bacterial enteropathogens in C. suis-infected suckling piglets.

Data on the evolution of blood metabolites and metabolic markers in neonatal piglets are scarce, although this information is vital to detect physiological aberrations from normal development. We aimed to characterize age- and nutrition-related changes in the plasma metabolome and serum biochemistry of suckling and newly weaned piglets and assess metabolite patterns as physiological markers for the two phases. In two replicate batches (n = 10 litters/group), piglets either received sow milk alone or were additionally offered creep feed from day 10 until weaning (day 28). Blood was collected from one piglet/litter on days 7, 14, 21, 28, 31 and 35 of life, totaling five females and five males/group/day. Signature feature ranking identified plasma triglycerides (TG) as discriminative for age and nutrition during the suckling phase. Influential TG 20:4_36:5, TG 17:0_34:2 and TG 18:2_38:6 were higher in creep-fed piglets on days 14, 21 and 28 of life, respectively, compared to only sow milk-fed piglets. Metabolites belonging to pathways within histidine, D-glutamine and D-glutamate metabolism as well as hippuric acid were distinctive for the postweaning compared to the suckling period. In conclusion, plasma lipid profiles especially corresponded to the type of nutrition in the suckling phase and showed a strong weaning effect.

Postnatally, short-chain fatty acids (SCFA) are important energetic and signaling agents, being involved in host nutrition, gut imprinting and immune and barrier function. Whether SCFA exert similar effects during the late fetal phase has been insufficiently elucidated. This study aimed to evaluate whether the fetal jejunum senses SCFA and whether SCFA modify the muscle tension and epithelial permeability and related signaling in jejunal tissue from the porcine fetus in late gestation. Exposure of fetal jejunal tissue to a mix of SCFA (70 µmol/mL) in an organ bath for 20 min lowered the muscle tension. Moreover, SCFA decreased the transepithelial conductance while increasing the short-circuit current in the Ussing chamber, indicating reduced permeability and increased SCFA absorption. Gene expression in the tissues harvested from the Ussing chamber after 30 min indicated downregulation of the expression of receptors (i.e., FFAR2 and TLR2), MCT1 and tight-junction and adherens proteins, which may be a negative feedback response to the applied high SCFA concentration compared with the micromolar concentration detected in fetal gastric fluid. Taken together, our data demonstrate that the fetal jejunum senses SCFA, which trigger electrophysiological, muscle contraction and related gene transcription responses. Hence, SCFA may play a role in prenatal gut nutrition and imprinting.

Weaning often leaves the piglet vulnerable to gut dysfunction. Little is known about the acute response of a gut mucosa primed by a milk-oriented microbiome before weaning to a plant-oriented microbiome (POM) after weaning. We evaluated the epithelial structure, secretory response and permeability in the small and large intestines of piglets receiving a milk-based (i.e. preweaning) or plant-based diet (i.e. postweaning) to POM inocula using intestinal loop perfusion assays (ILPA). The POM were prepared from jejunal and colonic digesta of four 7 week-old weaned (day 28 of life) piglets, having gut-site specific microbial and metabolite composition. Two consecutive ILPA were performed in 16 piglets pre- (day 24-27) and 16 piglets postweaning (day 38-41) in two replicate batches. Two jejunal and colonic loops per piglet were perfused with Krebs-Henseleit buffer (control) or the respective POM. The outflow fluid was analyzed for antimicrobial secretions. Jejunal and colonic loop tissue was collected after each ILPA for histomorphology and electrophysiology using Ussing chambers. ANOVA was performed using the MIXED procedure in SAS. The POM stimulated the secretory response by increasing mucin in the jejunal and colonic outflow by 99.7 and 54.1%, respectively, and jejunal IgA by 19.2%, whereas colonic lysozyme decreased 25.6% compared to the control (P &lt; 0.05). Fittingly, the POM raised the number of goblet cells by 96.7% in jejunal and 56.9% in colonic loops compared to control loops (P &lt; 0.05). The POM further flattened jejunal villi by 18.3% and reduced crypt depth in jejunal and colonic loops by 53.8 and 9.0% compared to the control (P &lt; 0.05); observations typically made postweaning and indicative for mucosal recognition of ‘foreign’ compounds. The POM altered the jejunal and colonic net ion flux as indicated by 22.7 and 59.2% greater short-circuit current compared to control loops, respectively; the effect being stronger postweaning (P &lt; 0.05). Colonic barrier function improved with age (P &lt; 0.05), whereas POM perfusion compromised the mucosal barrier as suggested by 17.7 and 54.1% greater GT and mucosal-to-serosal flux of fluorescein-isothiocyanate dextran, respectively, compared to the control (P &lt; 0.05). In conclusion, results demonstrated that the preweaning gut epithelium acutely responds to novel compounds in postweaning digesta by upregulating the first line of defense (i.e. mucin and lysozyme secretion) and impairment of the structural integrity.

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