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.
Highlights
MATERIALS AND METHODSSwine dysentery (SD) is an economically significant disease of growing pigs characterized by mucohemorragic diarrhea, or watery feces containing large amounts of mucus and flecks of blood [1]
Diarrhea during B. hyodysenteriae infection is driven by complete abolition of water absorption [5] and reduces apparent total tract digestibility of nutrients and energy, which contributes to attenuated growth performance [6]
Colon swabs collected from all pigs at necropsy and selectively cultured for B. hyodysenteriae confirmed that sham-inoculated pigs were culture negative and that the B. hyodysenteriaeinoculated PC and RS pigs were all culture positive at the time of necropsy (Table 2)
Summary
MATERIALS AND METHODSSwine dysentery (SD) is an economically significant disease of growing pigs characterized by mucohemorragic diarrhea, or watery feces containing large amounts of mucus and flecks of blood [1]. Upon association with the colonic epithelium, B. hyodysenteriae causes marked inflammation, hemorrhage, superficial epithelial necrosis, and excessive production of mucus [3, 4]. Diarrhea during B. hyodysenteriae infection is driven by complete abolition of water absorption [5] and reduces apparent total tract digestibility of nutrients and energy, which contributes to attenuated growth performance [6]. Inflammation at the colonic epithelium may alter intestinal metabolism to favor glycolysis, exacerbating dysbiosis [7]. Few studies have evaluated intestinal barrier permeability, digestive function, and intestinal metabolism in B. hyodysenteriaechallenged pigs. As the small intestine is the primary site of nutrient digestion and absorption [10], understanding if B. hyodysenteriae infection alters small intestinal integrity and function is highly relevant and applicable to developing mitigation strategies
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