The Effects of Muscle Thickness and Time on Feed on Hot Fat Trim Yields, Carcass Characteristics and Boneless Subprimal Yields

Abstract

Medium-framed, crossbred steers (n = 66), representing two muscle thickness classes (No. 1 and No. 2), were fed for 84, 112 or 140 d and slaughtered. Prior to chilling, one carcass side was trimmed of s.c. fat in excess of 6.4 mm and all internal fat USDA yield and quality grade factors were recorded for each untrimmed carcass side, whereas the trimmed side of each carcass was fabricated into boneless, closely trimmed (6.4 mm) subprimals. Slaughter weight did not differ (P > .05); however, No. 1 steers had heavier (P < .05) hot carcass weights (trimmed and untrimmed) than No. 2 steers, resulting in higher (P < .05) conventional and trimmed dressed yields. No. 1 steer carcasses possessed lower (P < .05) numerical yield grades than No. 2 carcasses, even though the two muscle thickness classes did not differ (P > .05) in fat thickness. Carcasses from No. 1 steers yielded a higher (P < .05) percentage of trimmed, boneless product than No. 2 carcasses. No. 1 steer carcasses yielded higher (P < .05) percentages of ribeye roll, strip loin and all subprimals from the round than No. 2 carcasses. Conventional and trimmed dressed yields (%) increased (P < .05) from 112 to 140 d on feed, whereas trimmed dressing percentages were similar (P > .05) for steers fed 84 or 140 d. Days on feed did not influence the percentage of trimmed, boneless subprimals derived from hot trimmed sides, indicating that hot fat trimming was effective in reducing variation in carcass cutability.