The present invention relates to a bile salt adjuvantfor animals for improving fat utilization efficiency inthe bodies of the animals, and to animal feed comprisingsame. More particularly, the present invention relates toa bile salt adjuvant for animals comprising sodiumstearoyl-2-lactylate. The adjuvant is used in animal feedto improve fat utilization efficiency in the bodies oflivestock when ingested by said livestock, therebyreducing the amount of fat required to be used in animalfeed and improving productivity.