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Post-weaning diarrhea significantly contributes to the high mortality in pig production, but the metabolic changes in weaned piglets with diarrhea remain unclear. This study aimed to identify the differential metabolites in the urine of diarrheal weaned piglets and those of healthy weaned piglets to reveal the metabolic changes associated with diarrhea in weaned piglets. Nine 25-day-old piglets with diarrhea scores above 16 and an average body weight of 5.41 ± 0.18 kg were selected for the diarrhea group. Corresponding to the body weight and sex of the diarrhea group, nine 25-month-old healthy piglets with similar sex and body weights of 5.49 ± 0.21 kg were selected as the control group. Results showed that the serum C-reactive protein and cortisol of piglets in the diarrhea group were higher than those in the control group (p < 0.05). The mRNA expression of TNF-α, IFN-γ in the jejunum and colon, and IL-1β in the jejunum were increased in diarrhea piglets (p < 0.05), accompanied by a reduction in the mRNA expression of ZO-1, ZO-2, and CLDN1 in the jejunum and colon (p < 0.05); mRNA expression of OCLN in the colon also occurred (p < 0.05). Metabolomic analysis of urine revealed increased levels of inosine, hypoxanthine, guanosine, deoxyinosin, glucosamine, glucosamine-1-p, N-Acetylmannosamine, chitobiose, and uric acid, identified as differential metabolites in diarrhea piglets compared to the controls. In summary, elevated weaning stress and inflammatory disease were associated with the abnormalities of purine metabolism and the hexosamine biosynthetic pathway of weaned piglets. This study additionally indicated the presence of energy metabolism-related diseases in diarrheal weaned piglets.

Microbial fermentation has been widely used to preserve or improve the nutritional properties of food. Liquid feeding can increase feed intake and reduce the morbidity of piglets. The objective of this study was to evaluate the effects of a diet fermented with bacteria and enzymes and liquid feeding on growth performance, nutrient digestibility, digestive enzyme activity, microflora, and expressions of intestinal development-related genes in weaning pigs. A total of 198 piglets (Duroc × Landrace × Yorkshire) with body weights of 8.70 ± 0.45 kg were assigned to three groups with six replicates per treatment, and 11 weaned piglets per replicate according to the initial body weight and sex. The three dietary treatments (all nonpelleted diets) were a standard dry feed as the control (CON), a control diet supplemented with antibiotics (AB), and a liquid feeding with a fermented diet (LFD). The liquid feeding diet, having the same composition and proportion of each ingredient as the control diet, was prepared by storing the dietary cereals (corn, soybeans, etc.) and water (1:0.5, wt/wt) in a closed tank at 26–30 °C with enzymes and bacteria, and then adding the remaining dietary ingredients immediately before feeding. The whole trial lasted 42 days. On days 11 to 14 and 39 to 42, fresh faecal samples were collected to evaluate the apparent total tract digestibility of nutrients. Performance, digestibility, serum physiochemical parameters, intestinal barrier function, microbiota, and microbial metabolites were measured. The experimental data were subjected to analysis of variance using the GLM procedure of SAS for a complete randomized block design, with a “pen” as the experimental unit. The results showed that the AB increased (p < 0.05) average daily gain and reduced (p < 0.05) feed conversion (F/G) over the course of 1–14 days compared to the control. The liquid feeding group significantly increased (p < 0.05) average daily gain, average daily feed intake, and final body weight compared to the other two dietary groups. The digestibility of crude protein, ether extract, ash, gross energy, Ca, and P also improved in the liquid feeding group. Moreover, the liquid feeding group significantly decreased (p < 0.05) serum urea nitrogen and D-lactate concentrations, as well as the activity of diamine oxidase, and increased (p < 0.05) serum total protein and glucose concentrations on day 14. Furthermore, the liquid feeding group significantly increased (p < 0.05) mRNA expressions of zonula occludens-2 (ZO-2) in the jejunum and zonula occludens-1 (ZO-1), ZO-2, occludin, and claudin-1 in the ileum. In addition, microbiota measurement suggested an increase in Lactobacillus content and a decrease in Escherichia coli with higher (p < 0.05) concentrations of acetic acid, propionic acid, butyric acid, and total volatile fatty acids in the caecal and colonic digesta of piglets in the liquid feeding group. In conclusion, the diet in the liquid feeding group was able to increase palatability, improve nutrient digestibility, and modulate metabolism, which resulted in higher feed efficiency and better growth performance in the piglets.

Accumulating evidences demonstrate that fermented feed and liquid feeding exerted a great beneficial influence on growth performance and health in the pig industry. This experiment was conducted to evaluate the effects of fermented liquid feeding on the growth performance and intestinal function of pigs. Two hundred and eighty-eight 27-day-old weaned piglets (8.21 ± 0.27 kg) were randomly allocated to a control group (basal diet (CON)), an antibiotic group (basal diet supplemented with antibiotics (AB)) and a fermented liquid feeding group (basal diet with fermented liquid feeding (FLF)), with 6 replicates per treatment and 16 weaned piglets per replicate. The experiment lasted for 160 days. Fresh fecal samples were collected to evaluate the apparent total tract digestibility (ATTD) of nutrients from the last 4 days of each stage. The results are shown as follows: (1) Compared with the CON group, in the whole stage, the FLF diet significantly increased the final body weight (BW) and ADG of pigs (P < 0.05), and had a tendency to increase ADFI (P = 0.086), but had no effect on F/G. (2) The ATTD of dry matter (DM), crude protein (CP), ether extract (EE), crude ash (CA), crude fiber (CF), gross energy (GE), calcium (Ca) and total phosphorus (TP) in the FLF group was significantly elevated compared with those of the CON group at 8–20 kg stage (P < 0.05). Meanwhile, the ATTD of EE in the FLF group was significantly increased compared with that of the CON group at the 50–75 kg and 100–125 kg stages (P < 0.05), and the ATTD of Ca was higher than that of CON group at the 100–125 kg stage (P < 0.05). (3) Compared with that of the CON group, the level of serum leptin in the FLF group had a tendency to decrease (P = 0.054), the level of serum ghrelin in the FLF group was significantly elevated (P < 0.05) and the level of serum peptide YY in the FLF group was significantly decreased (P < 0.05). (4) The abundance of Lactobacillus in cecal and colonic digesta was observably enhanced in FLF group. Meanwhile, the abundance of Escherichia coli in cecal and colonic digesta were dramatically reduced in the FLF group compared with that in the CON and AB groups (P < 0.05). (5) The levels of acetic acid in colonic digesta were significantly increased in the FLF group (P < 0.05), and an increasing trend was observed in total VFA in colonic digesta compared with CON (P < 0.1). The levels of acetic acid in colonic digesta were significantly promoted in the FLF group compared with that of the AB group (P < 0.05). In conclusion, these results indicate that fermented liquid feeding improved the growth performance of pigs, which might be associated with gastrointestinal hormone and intestinal functions.