Cows were adapted for 7 d to the initial diet. Cows then were weighed full on two consecutive days at the start, at d 42 and at d 84 of the trial to determine gain. Implants were removed 7 d prior to slaughter at the Univer- sity of Illinois Meat Science Laboratory. During the slaughtering-dressing procedure, liver and hot carcass weights were recorded for each animal. At 24 h postmortem, left sides were ribbed and USDA yield and quality grades (USDA, 1975) were determined by University of Illinois personnel. A 15-cm sample of the longissimus muscle was re- moved from the right side immediately poste- rior to the ribbed surface at the 12th rib at 24 h postmortem and frozen (-20~At approximately 72 h postmortem, each left side was boned completely without sepa- rating lean from fat (carcass soft tissue), and bone yields were recorded. Kidney, pelvic and heart fat (KPH) were included in the soft tissue of the carcass. During the boning process, the semitendinosus and biceps femoris muscles were removed carefully and trimmed of all extemal fat, and their individual weights were recorded. After bone yields were record- ed, carcass soft tissue from each side was ground three times and minced thoroughly, and a 5-kg random sample was obtained. This sample was ground finely and subsampled for moisture (100*C for 24 h) and fat (repetitive washes of warm chloroform:methanol) deter- minations using procedures described by Riss et al., (1983) The frozen longissimus muscle section was held (-20~ for approximately 2 mo. Frozen sections were cut into six steaks (2.5 cm thick) and wrapped individually. Two steaks were used for Wamer-Bratzler shear force determin- ation. Steaks were thawed (24 h at 4~ and cooked to an internal temperature of 70"C (AMSA, 1978) on a Farberware open-hearth grill monitored by copper constantan thermo- couples and a CS $250 Relay Scanner 5. Cooking loss was determined by comparing weights of steaks before and after cooking. After steaks cooled to room temperature, a minimum of eight core samples were removed and sheared using an Instron Universal Testing Machine 6 fitted with a Warner-Bratzler shear device. Two steaks for sensory panel evaluation were prepared in the same manner and served warm to a six-member, experienced sensory panel. Evaluations were made on a continuous 15-point scale for overall tenderness, juiciness, beef flavor intensity, off-flavor intensity and overall desirability (15 = extremely juicy, tender, desirable, flavorful or no off-flavor; 0 = extremely dry, tough, undesirable, bland or extreme off-flavor).