Chaff is the dry, scaly protective casings of the seeds of cereal grain, or similar fine, dry, scaly plant material such as finely chopped straw. Livestock can eat it and in agriculture it is used as livestock fodder,
Because ponies are so prone to laminitis or as they call it grass founder in the UK, special feeds are available like we don't see in NA and I wish we did. When hay prices went thro the roof one year I fed fodder in addition to hay for it's roughage. My costs went up very little and the horses wintered very well.