The incidence of swine dysentery in pigs can be reduced by feeding diets that limit the amount of fermentable substrate entering the large intestine.

Two experiments were conducted to test the hypothesis that feeding diets which limit the amount of fermentable substrate entering the large intestine would protect pigs against experimental infection with Serpulina hyodysenteriae, the causative agent of swine dysentery. Experiment 1 examined the effect of grain processing (hammer milling vs. steam flaking) and grain type (barley, groats, corn, sorghum and wheat) on indices of fermentation in the large intestine and the incidence of swine dysentery. Experiment 2 examined the role of five diets, steam-flaked corn, steam-flaked sorghum, hammer-milled wheat, extruded wheat and cooked white rice, on these same measures. All diets contained an animal protein supplement and no antibiotics. Pigs fed diets based on steam-flaked corn and steam-flaked sorghum had a lower incidence of disease (11-33%) than pigs fed diets based on other grains (75-100%). Pigs fed the diet based on cooked white rice were fully protected against swine dysentery. Both the soluble non-starch polysaccharide (NSP) concentration and the total NSP concentration of the diets explained a significant proportion of the variation in swine dysentery (R2 = 0.56, P = 0.016, and R2 = 0.71, P = 0.002, respectively), such that pigs eating diets containing <1.0 g/100 g soluble NSP showed reduced disease. However, pigs fed corn, sorghum and steam-flaked sorghum (Experiment 2), which contained only 0.4-0.5 g/100 g soluble NSP, still had a high incidence of disease (>50%). This was attributable to a higher level of resistant starch present in these grains. These data provide evidence that the expression of swine dysentery is associated with an increased concentration of fermentable substrate entering the large intestine.