Evidence presented indicates that moderate levels of insoluble fiber, in coarse particle size and when pigs already have compromised health status, may actually improve gut health during the first two weeks post-weaning. These positive effects are attributed to enhanced maturation of the gastrointestinal tract (GIT) as well as with the physical effect of fiber on the growth of intestinal microbiota and the blocking of the adhesion of pathogenic bacteria on the GIT mucosa.

In contrast, inclusion of soluble, and especially rapid fermentable, fiber in the diet for the first two weeks post-weaning, combined with early weaning and poor health status, might be contraindicative due to the limited digestive capacity of piglets. But, once pigs adapt to eating sufficient solid feed, higher amounts of soluble and fermentable fiber sources can be gradually included in the diet to promote healthy fermentation of undigested nutrients and better absorption of beneficial short-chain fatty acids by the colon mucosa.

In conclusion, under poor hygiene conditions, the level of fermentable fiber and crude protein in post-weaning diets should be limited to avoid intestinal dysbiosis, which might increase the risk of post-weaning diarrhea.