In general ‘high fiber’ ingredients present challenges to pelleting because fiber does not absorb moisture from steam conditioning very well (so you have difficulty in getting temperature into the mash), fiber does not compress easily into the die holes (size reduction of the fiber is important), may require a reduction in feed-rate, a change to a die with a different L/d ration and resetting of the die-roller interface. There is no ‘one-size-fits-all’ answer as there are many types of fiber.