Summary and Implications
The objective of the current study was to evaluate heritability and repeatability of serially measured ultrasound 12–13th rib fat thickness (UBF) and rump fat thickness (URF) measures in purebred Angus bulls and heifers.Data included 5000 observations from 912 bulls and heifers.Results from multiple trait analysis showed h2 of 0.29 and 0.40 for yearling UBF and URF, respectively.However, the difference in h2 estimates between yearling measures based on random regression models was smaller.At one year of age, h2 of URF was 0.37 as compared to 0.33 for UBF.Heritability and repeatability values were at their optimum at one year of age. Therefore, yearling bull and 13 to 14 months old heifer ultrasound subcutaneous fat thickness measures from good quality images can be used to evaluate genetic potential of next generation parents in Angus cattle.Information from URF measures may not have an apparent advantage in terms of improving rate of genetic change in percentage retail product in yearling Angus cattle than what could be achieved through selecting against 12th and 13th rib fat thickness.
Iowa State University
Hassen, Abebe T.; Wilson, Doyle E.; Rouse, Gene H.; and Tait, Richard G. Jr.
"Trends in Genetic Parameter Estimates for Ultrasound Back Fat and Rump Fat Thickness Measures in Angus Bulls and Heifers,"
Animal Industry Report:
AS 650, ASL R1868.
Available at: http://lib.dr.iastate.edu/ans_air/vol650/iss1/27