Journal of Animal Science, Vol 71, Issue 10 2623-2630, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Genetic parameter estimates of ultrasound-measured longissimus muscle area and 12th rib fat thickness in Brangus cattle

M. Z. Johnson, R. R. Schalles, M. E. Dikeman and B. L. Golden
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506.

Data from 2,101 Brangus calves born from 1986 to 1990 were analyzed with a REML procedure using a derivative-free algorithm in a mixed linear animal model to obtain variance component estimates of ultrasound-measured longissimus muscle area and fat thickness. Direct additive heritabilities (ha2) of .39 and .40 were obtained for age-constant weaning and yearling longissimus muscle area (WLMA and YLMA, respectively), with a genetic correlation (rg) of .66 between them. The rg of YLMA with birth weight (BWT), weaning weight (WWT), postweaning gain (PWG), yearling weight (YWT), frame score (FS), and scrotal circumference (SC) were .17, .29, .43, .38, .01, and .19, respectively. The ha2 of age-constant yearling 12th rib fat thickness (FAT) was .14, and cattle averaged .44 cm (SD = .19). Positive rg were obtained between FAT and WLMA (.19) and YLMA (.12). Negative rg of FAT with WWT, YWT, and SC were -.17, -.53, and -.33, respectively. Positive rg were obtained between FAT and BWT (.52), PWG (.44), and FS (.14). Maternal heritabilities (hm2) of WLMA, YLMA, and FAT were .01, .01, and .10, respectively. Weight-constant WLMA, YLMA, and FAT ha2 were .36, .39, and .11, respectively. Selection based on either age-constant YLMA or FAT could potentially result in 1.06 cm2 or .005 cm change per year, respectively, which would be slightly greater than change from selection based on weight-constant YLMA or FAT. Selection based on WLMA or YLMA should be effective, and changes in these traits, growth, and SC should be possible in tandem.(ABSTRACT TRUNCATED AT 250 WORDS)

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