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Title: GENETIC AND PHENOTYPIC PARAMETERS FOR CARCASS TRAITS OF AMERICAN SHORTHORN BEEF CATTLE

Author
item PARIACOTE, F.
item Van Vleck, Lloyd
item HUNSLEY, ROGER

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Traits of beef cattle can be categorized as growth, reproduction, and carcass. Measurements on carcass traits are costly to obtain in numbers necessary for genetic analysis. Genetic analyses are necessary 1) to determine if any of the differences in animals are due to genetic differences and 2) to determine if genetic antagonisms exist among the traits. A genetic antagonism exists if selection to improve one trait results in deterioration of another trait. Carcass measurements for 1,323 Shorthorn steers were subjected to genetic analysis. Traits included hot carcass weight, dressing percentage, fat depth, internal fat, ribeye area, marbling score, quality grade, and yield grade. Heritability estiamtes were all greater than 50%, which indicates selection can be effective in changing these traits if measurements were available. Genetic antagonisms were found between fat depth over the rib and ribeye area and between internal fat and ribeye area. Opportunity seems to exist to improve marbling score without decreasing carcass weight per day of age and without increasing internal fat. These results are based on progeny of a limited number of sires with few progeny per sire.

Technical Abstract: Measurements from 1,323 steers collected by The American Shorthorn Association were used to estimate heritabilities of and genetic and phenotypic correlations among carcass traits. Records were classified by herd of origin, slaughter group, and individual month of birth. Relation- ships were through sires. Sire of sire and dam of sire identification were efound for each sire. Measurements for slaughter weight; hot carcass weight; dressing percentage; fat thickness; kidney, pelvic and heart fat; ribeye area; marbling score; quality grade; hot carcass weight per day of age, and yield grade were analyzed with a REML algorithm. A single trait model with fixed effects and sire and dam as random effects was used. Estimates of heritability were about .50 and larger. Carcass weight measurements had lower heritability than marbling score and quality grade. Genetic correlations were estimated with a multitrait REML algorithm. Correlations for carcass weight with marbling score and quality grade were negative and nearly zero. Fat measurements were negatively correlated with carcass weight and positively correlated with marbling score and quality grade. Carcass weight was positively phenotypically correlated with all traits and ribeye area was negatively correlated with fat measurements, quality traits and yield grade. Results suggest greater genetic variation for marbling score and quality grade than for hot carcass weight and that a genetic antagonism exists between ribeye area and meat quality traits. Opportunity exists for breeding plans to improve marbling without adverse genetic effect on hot carcass weight per day of age and without increasing fat deposition in the kidney, pelvic and heart area.