Disclosed herein is the use of a cashew nut shell liquid for the manufacture of a rumen fermentation improving agent for a ruminant. Also disclosed is the use of cashew nut shell liquid for the manufacture of a feed for improving rumen fermentation in a ruminant, wherein the feed further includes an additive selected from alginic acid, sodium alginate, xanthan gum, casein sodium, gum Arabic, guar gum or water soluble polysaccharides including tamarind seed polysaccharide.
