What the Heck Is fibre rich feed for horses?

http://www.kentuckynewsdesk.com/news/story/582403/with-half-of-britains-horses-overweight-bifid-launches-grainfree-lowsugar-feed-for-the-nations-gooddoers.html

Gentle horse feed for sensitive stomachs, designed to support digestive comfort, hindgut health and easy nutrient absorption. A low-starch fibre-rich formula with natural ingredients to help maintain settled digestion and overall health.