Feed additives for ruminants comprises tablets or granules of a mixture of biologically active ingredient(s), chitosan and protective material(s) which are one or more substance(s) selected from the group consisting of saturated or unsaturated aliphatic mono-carboxylic acids having 14 to 22 carbon atoms, hardened vegetable oils and hardened animal oils.By containing chitosan, said feed additives easily pass through the rumen and are easily digested by digestive organs from abomasum, consequently said biologically active ingredient(s) are efficiently absorbed by oral feeding to ruminants.