Document Type


Extension Number

ASL R1823

Publication Date



The present study included 3,066 ultrasound-predicted percentage of intramuscular fat (UPFAT) and 4,502 ultrasound ribeye area (UREA) measures of bulls and heifers from the Iowa State University beef cattle breeding project. Data were collected over a four-year period between 1998 and 2001. The objective of the current study was to estimate variance components and heritability of UPFAT and UREA. Data were analyzed based on single- and multiple-trait animal models. Heritability of UPFAT increased from a minimum of 0.36 at a mean age of 37 weeks to a maximum of 0.54 at a mean age of 54 weeks. Heritability of UREA ranged from 0.30 at a mean age of 35 weeks to a maximum of 0.48 at a mean age of 50 weeks. Heritability of yearling UPFAT and UREA were 0.50 and 0.45, respectively. For the range of ages included in the present study the results suggest optimum heritability of UPFAT and UREA starting at about one year of age.

Copyright Owner

Iowa State University



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