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Title: GENETIC AND PHENOTYPIC (CO) VARIANCES FOR GROWTH AND CARCASS TRAITS OF PUREBRED AND COMPOSITE POPULATIONS OF BEEF CATTLE

Author
item Gregory, Keith
item Cundiff, Larry
item KOCH ROBERT M - UNIV OF NEBRASKA

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Lack of product consistency is a problem with beef. Variation within composite populations and contributing purebreds is similar for carcass and meat traits. Composite breeds offer an effective procedure to use breed differences to achieve and maintain the carcass composition and beef quality attributes that more nearly approach the optimum for each of a wide erange of production and marketing situations. Because genetic variances are similar for composite populations and contributing purebreds for growth and carcass and meat traits, selection response is expected to be similar within populations of each. Because of the high genetic correlation between marbling score and other measures of fat in the carcass, simultaneous selection to increase marbling and to increase percentage of retail product is unlikely to be effective. The low phenotypic correlation between marbling score and palatability attributes of cooked steaks indicates marbling score does not have high predictive value of end use properties of beef in young cattle fed and managed alike to an average slaughter age of 438 days. All segments of the beef industry and consumers will benefit from this information.

Technical Abstract: Least squares means, genetic and phenotypic standard deviations, and phenotypic coefficients of variation, were estimated for growth, carcass, and meat traits of castrate males for nine purebreds and for three compo- site populations to which the nine purebreds contributed. Also, herit- abilities and genetic and phenotypic correlations were estimated among growth, carcass, and meat traits for 1,594 individuals that were the pro- geny of 306 sires. For growth and size related traits, phenotypic standard deviations tended to be slightly larger for composites than for contribut- ing purebreds because of the higher means for composites. Coefficients of variation and genetic standard deviations were not different between composites and contributing purebreds for growth and size related traits. For traits relating to carcass and meat quality, composites and contribut- ing purebreds did not differ in phenotypic standard deviations or coeffic- ients of variation. Generally, estimates of genetic standard deviations and heritabilities did not differ among populations. Generally, genetic correlations were high among all measures of carcass fat indicating major difficulty in achieving a high percentage of retail product simultaneously with a high fat content of the longissimus muscle which is required for carcass quality grade. All phenotypic correlations of marbling score or ether extracted fat in the longissimus muscle with all end use properties relating to palatability attributes were below .30. Thus, marbling score or longissimus muscle fat are not criteria of great value for predicting differences in palatability characteristics of cooked steaks.