Testosterone propionate implants used in Exp. 1 and 2 were prepared as described by Kesler (1987). Implants were made of medical grade silastic tubing 2 with an inside diameter of .635 cm and an outside diameter of .953 cm. The daily release rate of compound from full implants previously was determined to be .63 mg/cm in length (Kesler, 1987) and release of testosterone propionate continued for at least 180 d. Because of their large size, these implants were subcutaneously inserted behind the shoulder and over the dorsal aspect of the rib cage of the cattle.