A method is discussed for adding Rumensin t o a 72-percent-concentrate receiving ration for newly arrived feedlot replacement calves, without adversely affecting feed consumption, body weight gain, or animal health.

Additional members of the Calf Study Group are: Joseph G. Clark D. V.M., Brawley; John R. Dunbar, Animal Scientist, Cooperative Extension, Davis; Glen P. Lofgren, Clayton Livestock Research Center, University of New Mexico; Ben B. Norman, Veterinarian, Coopemtive Extension, Davis; and Edward C: egge. Assistant Professor, University of West Virginia