What the Heck Is grain free forage replacer UK?

http://gujaratmagazine.in//story/199063/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 comfortable digestion, hindgut health and efficient nutrient uptake. A low-starch high-fibre formula with natural ingredients to help maintain steady digestion and overall wellbeing.