What the Heck Is high fibre horse feed?

https://horse-feed-brands555.hexaforgey.com/posts/which-horse-feed-is-best-for-horses-suffering-from-ulcers

Gentle horse feed for sensitive stomachs, designed to support gut comfort, hind gut health and easy nutrient absorption. A low sugar high-fibre formula with natural components to help maintain steady digestion and general wellbeing.