The purpose of the present invention is to provide an additive composition for ruminant feeds, which contains a biologically active substance at a high concentration, is of a dispersed type, can be highly protected in a rumen, and has excellent elution properties in a digestive tract. The present invention relates to an additive composition for ruminant feeds, which is characterized by containing (A) at least one component selected from a hydrogenated vegetable oil and a hydrogenated animal oil each having a melting point of 50 to 90°C exclusive, (B) a surfactant in an amount of 0.01 to 6% by weight inclusive, (C) a biologically active substance (excluding L-lysine and a salt thereof) in an amount of 16 to 72% by weight inclusive, and (D) L-lysine or a salt thereof in an amount of 1 to 40% by weight inclusive.
