Estimation of Heritability and Repeatability of Ultrasound Ribeye Area Measures Using Random Regression Models
The present study included 4,653 observations from 882 Angus bulls and heifers born during the spring of 1998 to 2001. Each year cattle were scanned four to eight times for ribeye area (UREA) and other ultrasound traits, starting at a minimum age of 27 weeks. The objective of the current study was to estimate variance components, heritability, and repeatability of UREA. Direct additive genetic variance increased from 7.11 to 19.4 cm4 as measurement age increased from 27 to 62 weeks. For the same time period direct permanent environmental variance increased from 14.7 to 26.6 cm4. When averaged by four weeks intervals, heritability of UREA ranged from 0.29 to 0.39. Mean repeatability values ranged from 0.80 to 0.86. Yearling heritability and repeatability were estimated at 0.39 and 0.80, respectively. For the range of ages considered, the present results showed an optimum heritability and repeatability of UREA measures around 52 weeks through at least 62 weeks of age.