Brachyspira hyodysenteriae Infection Reduces Digestive Function but Not Intestinal Integrity in Growing Pigs While Disease Onset Can Be Mitigated by Reducing Insoluble Fiber

Abstract

Swine dysentery (SD) induced by Brachyspira hyodysenteriae manifests as mucohemorrhagic diarrhea in pigs, but little is known about the changes that occur to the gastrointestinal tract during this disease. It is thought that dietary fibers alter disease pathogenesis, although the mechanisms of action are unclear. Thus, the objectives of this study were to characterize intestinal integrity, metabolism, and function in pigs during SD and determine if replacing insoluble fiber with fermentable fibers mitigates disease. Thirty-six B. hyodysenteriae-negative gilts [24.3 ± 3.6 kg body weight (BW)] were assigned to one of three treatment groups: (1) B. hyodysenteriae negative, control diet (NC); (2) B. hyodysenteriae challenged, control diet (PC); and (3) B. hyodysenteriae challenged, highly fermentable fiber diet (RS). The NC and PC pigs were fed the same control diet, containing 20% corn distillers dried grains with solubles (DDGS). The RS pigs were fed a diet formulated with 5% sugar beet pulp and 5% resistant potato starch. On days post inoculation (dpi) 0 and 1, pigs were inoculated with B. hyodysenteriae or sham. Pigs were euthanized for sample collection after onset of SD. The challenge had high morbidity, with 100% of PC and 75% of RS pigs developing clinical SD. The timing of onset of clinical SD differed due to treatment, with RS pigs having a delayed onset (dpi 9) of clinical SD compared with dpi 7 for PC pigs. Colon transepithelial resistance was increased and macromolecule permeability was reduced in PC pigs compared with NC pigs (P < 0.01). Minimal changes in ileal permeability, mitochondrial function, or volatile fatty acids (VFAs) were observed. Total VFA concentrations were lower in the colon and cecum in both PC and RS pigs compared to NC pigs (both P < 0.05), but iso-acids were higher (both P < 0.05). Total tract digestibility of dry matter (DM), organic matter (OM), nitrogen (N), and gross energy (GE) was lower in PC pigs compared with both NC and RS pigs (both P < 0.001). These data indicate that SD reduces digestive function but does not reduce ex vivo intestinal integrity. Further, replacement of insoluble fiber with highly fermentable fibers mitigated and delayed the onset of SD.

Highly Fermentable Fiber Alters Fecal Microbiota and Mitigates Swine Dysentery Induced by Brachyspira hyodysenteriae

“…We have previously demonstrated that replacing corn DDGS with highly fermentable sugar beet pulp and resistant potato starch delays onset and reduces severity of B. hyodysenteriae challenge [ 16 ]. However, longitudinal growth performance during the recovery phase of disease was not evaluated.…”

Alteration of Colonic Mucin Composition and Cytokine Expression in Acute Swine Dysentery

“…Alterations in dietary insoluble fiber have been shown to affect the intestinal microbiome in pigs and may predispose to the development of SD in previous studies. 8,30,80 In the past few decades, commercial swine diets have increased the use of distiller’s dried grains with solubles (DDGS), which is a coproduct of biofuel production. 73 DDGS have relatively more insoluble dietary fiber than whole corn and this fiber passes through to the colon where it is fermented.…”

Lawsonia intracellularis infected enterocytes lack sucrase-isomaltase which contributes to reduced pig digestive capacity

“…Mitochondria were isolated from ileum and colon tissue via differential centrifugation as previously described [ 16 ]. Washed mitochondria were resuspended in 3 mL mitochondrial wash buffer, protein concentrations were determined via BCA assay (Thermofisher Scientific), and were diluted to a protein concentration of 2 mg/mL and stored at 4 ℃ until use [ 16 ].…”

“…Mitochondrial reactive oxygen species (ROS) production was determined in isolated mitochondria using a 2′,7′-Dichlorofluorescin diacetate (DCFH) assay described previously [ 16 – 18 ]. Mitochondrial hydrogen peroxide production was calculated from a hydrogen peroxide standard curve based on fluorescence values of DCFH.…”

“…Mitochondrial oxygen consumption was evaluated using a Seahorse XFe24 Extracellular Flux Analyzer (Seahorse Bioscience, North Billerica, MA, USA) as previously described [ 19 – 21 ]. Mitochondria (40 μg protein) were plated into a V7 XFe24 Tissue Culture Plate, diluted with mitochondrial assay buffer (220 mM Mannitol, 70 mM Sucrose, 5 mM KH 2 PO 4 , 5 mM MgCl 2 , 2 mM HEPES, 1 mM EGTA, 0.5 mg/mL BSA, pH 7.4), and centrifuged (2000 × g for 10 min at 4 °C).…”