The amount of fiber in the diet of a ferret should be no more than five percent, and it is probably best if it is only two to three percent. (petbusiness.com)
He also has to be mindful of getting enough fiber in his diet so he doesn't always alternate between loose stools and constipation. (healthcentral.com)
They are what help those probiotics do their thing, plus you're getting the added benefit of more fiber in your diet. (ourpaleolife.com)