Dean, Dustin Tyler (2003-05). Evaluation of ultrasound and other sources of information to predict beef carcass traits and final carcass value. Doctoral Dissertation. Thesis uri icon

abstract

  • Purebred Beefmaster steers (n = 160) from five owners were fed at a commercial
    feedlot in South Texas beginning in November of 2004; 68 steers possessed pedigree
    information. Beginning in mid-November, steers were individually weighed and
    evaluated for ultrasound body composition at 56-d intervals by a certified technician.
    Feeder calf frame (FRM) and muscle (MUS) scores were assigned at initial ultrasound
    evaluation. Steers were fed and marketed through a lean-based, branded beef program
    and were harvested in two groups in May and June of 2005 at a commercial beef plant.
    Analyses were conducted to investigate the ability to predict carcass traits from the
    different sources of information available on these cattle. Evaluation of carcass traits
    were investigated using four sets of independent variables referred to as sources A, B, C,
    or D and ultrasound scan session (1 ?? 4). An analysis included initial weight at first scan
    session (IWT), FRM and MUS as independent variables through GLM procedures. B
    analyses utilized ultrasound measures of the longissimus area, intramuscular fat, fat
    thickness, rump fat, and gluteus medius depth along with IWT as independent variables.
    Multiple regression was performed on each carcass trait using IWT and ultrasound traits
    at each scan session. Mallow??s CP was used to select a model that best described each carcass trait. C analyses (GLM) utilized variables from A and B analyses combined plus
    ranch. D analyses (GLM) included variables from C analyses plus sire nested within
    ranch. Respective R-square values (scan 1 ?? 4) for marbling score were .02, .04, .05, and
    .10 using A information, .14, .17, .42, and .54, using B information, .35, .35, .47, and .55
    using C information, and .56, .59, .65, and .76 using D information. R-square values
    ranged from .34 to .86 for carcass weight, .11 to .77 for fat thickness, .06 to .82 for ribeye
    area, and .10 to .81 for yield grade. Ultrasound data obtained closer to harvest and
    increasing amount of data related to genetic and management background showed
    increased R-square values, but may be best utilized in conjunction with one another to
    predict carcass traits and final carcass value.

publication date

  • May 2003