Acute Phase Protein and Microbial Metabolite Response to an Enterotoxigenic Escherichia coli Challenge in Weaned Pigs Fed Higher Fiber Diets with or without Carbohydrases

The objective of this study was to evaluate the impact of soluble (10% sugar beet pulp) versus insoluble dietary fiber (15% low fat corn DDGS) with or without the addition of exogenous carbohydrases on serum acute phase proteins (APP) and digesta VFA in weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC). Sixty newly weaned piglets (6.9±0.07 kg) were preselected for the F18 ETEC sensitivity genotype. Pigs were randomly assigned to 1 of 6 treatments (n=10/trt) including: 1) PC: non-challenged, 2) NC: F18 ETEC challenged, 3) SF: NC + soluble fiber, 4) IF: NC + insoluble fiber, and 5, 6) SFE and IFE: SF or IF with exogenous enzymes (xylanase, ß-glucanase, and pectinase). Pigs were housed individually and then orally challenged with ETEC on d 7 (0 day post inoculation, dpi) post weaning. Blood samples were collected on dpi -1, 3, and at necropsy (dpi 7 or 8) to determine circulating concentrations of APP. Colon contents were collected at necropsy for VFA analysis. Data were analyzed using PROC GLIMMIX (SAS 9.4) with pen as the experimental unit. There was no difference in serum haptoglobin or C-reactive protein (CRP) between PC and NC on any collection day (P>0.10). On dpi 3, enzyme supplementation (SFE+IFE) decreased haptoglobin concentration regardless of fiber source (P<0.05). Serum haptoglobin on dpi 3 was lower in SFE, but not PC, SF, IF, or IFE, compared to NC (0.11 vs. 0.40 mg/mL; P<0.05). Fiber and carbohydrases did not affect CRP compared to NC on any collection day (P>0.10). Regardless of dietary treatment, pigs had higher serum haptoglobin and CRP levels on dpi -1 than dpi 3 and at necropsy (P<0.05). Pigs in the PC group had higher total VFA (107.3 vs. 87.1 uM/g; P<0.05) and tended (P<0.10) to have a higher concentration of acetic and propionic acid in the colon than those in NC. Soluble fiber increased colonic acetic acid, butyric acid, and total VFA concentration compared to NC (P<0.05). Insoluble fiber, regardless of enzyme addition, had no impact on any colonic VFA (P>0.10). In conclusion, SFE may reduce serum APP compared to other diets. Soluble fiber, but not IF, regardless of enzyme addition, may have improved colonic VFA production during an ETEC challenge. This may stimulate gut health and help the pig respond to ETEC, which may partly explain our previous findings that soluble fiber improved growth rate and reduced ileal epithelial E. coli attachment.