Masterfeeds Rx Roughage (cube) is a high fibre pellet or cube, which is used as a high fibre feed, and as a hay stretcher and extender at times when hay is in short supply, or for horses who struggle consuming hay due to problems with their teeth such as senior horses. Fortified with a lower level of vitamins and minerals it is safe to be fed at very high levels as a complete hay replacement when needed. Ideally however some long stem hay should be provided.