In animal feed, a filler is an ingredient added to provide dietary fiber, bulk or some other non-nutritive purpose.
[1] As sources of dietary fiber, a filler has little inherent nutritional value for a monogastric (non-ruminant) animal insofar as calories are considered.
Adding too much fiber makes the food less palatable, so a balanced amount should be given,[5] or else there will be reduced nutrient intake and poorer coat and skin quality.
Again like in humans, fermentable fibers feed the gut microbes, and too much of it would cause flatulence, soft stools, even diarrhea.
[citation needed] In rare cases, contaminated fillers have led to large-scale recalls at significant expense to the pet food companies.