Maulsby, Richard Paul. (2009-12). Evaluation of Early Measures of Body Composition as Related to Beef Carcass Traits. Master's Thesis. Thesis uri icon

abstract

  • Two similarly managed trials were conducted to investigate serial ultrasound

    measures of body composition (longissimus muscle area (ULMA), 12th - rib fat

    thickness (UFAT), and percentage of intramuscular fat (UIMF)) early in the lives of

    feeder calves as they compared to carcass traits. Group 1 cattle were Charolais-sired by

    Brahman-British crossbred dams whereas Group 2 cattle were purebred Beefmaster.

    Both groups were fed at the same commercial feedlot (Graham Land and Cattle Co.) in

    Gonzales, Texas. In both data sets classifications were developed for ribeye area of

    Lower (less than 70.95 cm2, Middle (between 70.95 cm2 and 90.3 cm2) and Upper (over

    90.3 cm2) based on a range that fit within the ribeye specifications of such branded beef

    programs as Certified Angus Beef and Nolan Ryan?s Tender Aged Beef. Differences

    among ribeye area and quality grade (Choice vs. Select) categories were evaluated for

    ultrasound and carcass traits. As reported previously, correlations between ultrasound

    measures and carcass traits became larger at times closer to harvest. In both sets of

    cattle, there were no differences in fat thickness or intramuscular fat at the ultrasound

    scan sessions or in these carcass traits due to ribeye area category. The same trend for quality grade classification was not seen across both groups of cattle however. In Group

    1, there were no differences in early measures of body composition between carcass

    quality grade classes except for ultrasound fat thickness at weaning. However, in Group

    2 cattle there were differences in ultrasound fat at times 1 and 2, IMF at time 1, and

    ribeye area at time 2 between cattle that graded choice verses those that graded select.

    Correlations between ultrasound measures of REA (r of .26 to .50) and ultrasound REA

    and carcass REA (r of .16 to .81) appeared to be lower in Group 1 vs. Group 2 (r of .55,

    and .64 to 81 respectively). Results from this project imply that changes in ribeye area

    will not automatically result in changes of marbling and vice versa. Furthermore, these

    results also show that ultrasound is useful to help predict beef carcass traits, but that

    early measures of body composition used alone do not explain a large portion of the

    variation in the carcass measures and specific methods should be developed by different

    biological cattle types.

publication date

  • December 2009