Author
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UTRERA, ANGEL - UNIV. OF NEBR-LINCOLN |
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Van Vleck, Lloyd |
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Submitted to: Genetics and Molecular Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/1/2003 Publication Date: 1/4/2004 Citation: Utrera, A.R., Van Vleck, L.D. 2004. Heritability estimates for carcass traits of cattle: A review. Genetics and Molecular Research 3(3):380-394. Interpretive Summary: This review of estimates of heritability published in the scientific literature during the last 42 years for carcass traits revealed that most estimates were on an age constant or a time on feed constant basis. Carcass weight, backfat thickness, longissimus muscle area and marbling score were the carcass traits with the most estimates of heritability. The average estimates indicate that they are similarly and moderately heritable (0.35 ' 0.40). In contrast, the number of estimates of heritability for dressing percentage was about half as many as those for the four carcass traits listed above. The average estimate also indicates that dressing percentage is moderately heritable. Carcass traits with fewest estimates of heritability in the literature were traits that require the most effort to measure: kidney, pelvic, and heart fat percentage, yield grade, predicted percentage of retail product, retail product weight, fat weight, bone weight, actual retail product percent, fat percent, and bone percent. The estimates, however, indicate these traits are more heritable, except for kidney, pelvic, and heart fat percentage and predicted percentage of retail product, than the more frequently studied carcass traits. Yield grade had the smallest number of heritability estimates, but the largest estimates of heritability. Heritability estimates for most carcass traits included in this review varied greatly, which could be due to differences in breed groups, methods of estimation, effects in the model, number of observations, measurement errors, sex, and management differences. Few studies have compared heritability estimates for carcass traits adjusted to different end points. Results from such studies, however, were inconsistent although some studies suggest that heritability estimates for several carcass traits were sensitive to the covariate (end point) included in the model implying that direct response to selection would be different for some traits depending on slaughter end point. The effect of different end points on estimates of heritability has not been studied for several carcass traits. Technical Abstract: The objective was to summarize estimates of heritability for carcass traits of beef cattle published in the scientific literature. The papers (n=72) that were reviewed were published from 1962 to 2004. Unweighted means of estimates of heritability for 14 carcass traits by slaughter end point (age, weight, and fat depth) were calculated. Over the three end points, the carcass traits with the most estimates of heritability (56' n '66) were carcass weight, backfat thickness, longissimus muscle area and marbling score. Means indicate that these traits are similarly and moderately heritable (0.40, 0.36, 0.40, and 0.37, respectively). Heritability estimates for most traits, however, varied greatly, which could be due to differences in breed groups, methods of estimation, effects in the model, number of records, measurement errors, sex, and management differences. Few studies have compared heritability estimates for carcass traits adjusted to different end points. Results from such studies were often inconsistent. Some studies, however, suggest that heritability estimates for several carcass traits were sensitive to the covariate included in the model as the end point. Differences in heritability imply that responses to selection would be different for some traits depending on slaughter end point. For many carcass traits, the effects of different end points on estimates of heritability and expected responses to selection have not been studied. |
