EFFECT OF HOT-FAT TRIMMING ON FACTORS ASSOCIATED WITH THE SUBPRIMAL YIELD OF BEEF CARCASSES

Thirty-two crossbred cattle (steers - 17; heifers = 15) exhibiting an ultrasound fat thickness at the 12 to 13th rib region of at least 10 mm were selected from a slaughter shift at a commercial packing plant. After splitting, alternating sides of each carcass were trimmed of 1) subcutaneous fat in excess of 6.4 mm; 2) all kidney, pelvic, and heart fat; and 3) all cod or udder fat and fat in the flank region. Both sides of each carcass were fabricated into subprimals (final trim level of 6.4 mm) according to normal industry procedures. Effect of hot-fat trimming, yield grade (8, 4, and 5), and gender on hot-fat trim, fabrication fat trim, major subprimal, and total subprimal yield of untrimmed and trimmed carcasses were determined. Higher numerical yield grade (YG) corresponded with higher (P < .05) percentages of hot-fat trim. Hot-fat trimming increased (P < .05) the difference in fabrication fat trim between steers and heifers and between YG 3 and YG 5. Steers and heifers differed (P < .05) in percentage of major subprimals and total subprimals when processed conventionally, whereas hot-fat trimming eliminated this difference (P < .05). Untrimmed YG 3 carcasses had 3.1 and 5.0% higher major subprimal yield (P < .05) than untrimmed YG 4 and YG 5 carcasses, respectively, whereas hot-fat trimming reduced this difference to 2.5% for YG 4 and to 3.7% for YG 5. A greater effect of hot-fat trimming was observed between YG 3 and YG 4 and between YG 3 and YG 5 carcasses for total subprimal yield: the difference was reduced to 1.9 and 2.3%, respectively. These results indicate that hot-fat trimming reduces differences in cutability between carcasses that, if processed conventionally, would have large differences in cutability.