CASE STUDY:Carcass and meat characteristics and M. longissimus thoracis histology of beef from calf-fed and yearling-fed Angus steers1
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2011 American Registry of Professional Animal Scientists. A study was conducted based on the proposal that cattle raised to a constant carcass weight would have comparable carcass composition regardless of being calf fed (CF) or yearling fed (YF). Twenty-four Angus steers were assigned to CF and YF groups and allotted to initial, intermediate, and terminal sampling periods (n = 4 for all groups and periods). Steers from the CF group were slaughtered at weaning (8 mo of age) or after consuming a corn-based diet for 4 mo (12 mo of age) or 8 mo (16 mo of age). Steers from the YF group were all pasture fed for 4 mo and then slaughtered either at 12 mo of age or after consuming the corn-based diet for 4 mo (16 mo of age) or 5.5 mo (17.5 mo of age). Carcass weight, percentage KPH, and YG values were the same in the terminal CF and YF groups. Marbling score, ribeye area, and fat thickness over the 12th thoracic rib increased quadratically (P = 0.02) at a decreasing rate over time and were not different between CF and YF steers. M. longissimus thoracis i.m. lipid and i.m. adipocyte size increased (P = 0.01) over time but did not differ between CF and YF steers. Slip point temperature of s.c. adipose tissue lipids decreased (P < 0.01) over time, indicating less saturated fat in this depot. Cholesterol concentration in M. longissimus thoracis did not increase with time on feed but tended (P = 0.06) to be greater in CF steers. Trained sensory panel evaluation indicated a trend (P = 0.07) toward greater juiciness between intermediate YF and terminal YF cooked loin samples, but there were no other differences in sensory panel traits between samples from CF and YF groups. Thus, even though the YF steers were older than the CF steers at each sampling period, there were few differences in carcass or beef characteristics between the terminal CF and YF steers that had achieved the same carcass weights.
