Two experiments were conducted to test the hypothesis that soluble non-starch polysaccharides (NSP) and resistant starch (RS) cause swine dysentery (SD) in pigs experimentally infected with the spirochete Serpulina hyodysenteriae. In Experiment 1, a source of soluble NSP (guar gum; GG), insoluble NSP (oat chaff; OC), resistant starch (retrograde cornstarch; RS) or a combination of GG and RS (GG + RS) was added to a diet containing cooked white rice (R), soybean meal (SBM) and animal protein (meat and bone meal, bloodmeal, fishmeal). A diet containing only cooked white rice, SBM and the sources of animal protein (AP) was also fed. In Experiment 2, three rice-based diets containing different levels of RS were fed to pigs. In Experiment 1, the pH of digesta in the cecum, proximal colon and distal colon of pigs fed diets R-GG, R-RS and R-GG + RS was lower (P < 0.001), and volatile fatty acid concentration higher (P < 0.001), than in pigs fed diets R-OC and R-AP. Pigs fed diets with RS and GG + RS had greater (P < 0.05) concentrations of ATP in the large intestine than pigs fed other diets. There were no significant differences in any fermentation indices measured in Experiment 2. In Experiment 1, pigs fed diets R-GG, R-RS and R-GG + RS were colonized with S. hyodysenteriae after experimental infection. However, only pigs consuming diets R-GG (4 of 5) and R-GG + RS (5 of 5) showed clinical signs of SD. Spirochetes were isolated from the feces of all pigs fed diets containing RS in Experiment 2. However, and in contrast to Experiment 1, 80-100% of pigs infected with S. hyodysenteriae displayed clinical signs of SD. These data confirm the role of fermentable carbohydrate in the pathogenesis of SD.

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The current study identified some potent dietary ingredients or plant compounds that can assist in developing novel feed additives for methane mitigation from the rumen.

M PS ON . 1998. Swine dysentery (SD) is a disease which can be controlled by feeding a diet low in dietary fibre. The influence of source and inclusion level of dietary fibre both on bacterial populations in the colon, and on subsequent development of SD in pigs experimentally infected with Serpulina hyodysenteriae was evaluated. In Experiment 1, pigs were fed a low-fibre diet based on cooked rice and an animal protein supplement, or the same diet containing added insoluble (iNSP, fed as oaten chaff) or soluble (sNSP, fed as guar gum) non-starch polysaccharides, resistant starch (RS), or a combination of the last two (sNSP/RS). In Experiment 2, different levels of RS were added to the diet. With the base rice diet and with the addition of iNSP, the total number of colonic bacteria was low, the Gram-positive population predominated, S. hyodysenteriae did not colonize and SD did not develop. Synergistic bacteria (Fusobacterium necrophorum and Fus. nucleatum), which have been reported to facilitate colonization by S. hyodysenteriae, were found only among isolates from pigs fed the sNSP/RS diet, and these animals developed SD. Addition of RS to the diet increased total bacterial counts and stimulated growth of Gram-negative bacteria in the colon. In Experiment 1, this permitted colonization by S. hyodysenteriae, but not expression of SD. In contrast, in Experiment 2, this level of inclusion and two others allowed both colonization and development of SD. In conclusion, the addition of sNSP and/or RS to an otherwise protective rice-based diet generated changes in the large intestine microbiota which might have some influence on proliferation of S. hyodysenteriae and the development of SD.