|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/1999
Publication Date: N/A
Interpretive Summary: Measurements on carcass traits of beef cattle are expensive to obtain. This analysis is the first reported for Korean Native Cattle (Han Woo breed). Three carcass traits (marbling score, dressing percentage, and ribeye area) and three measures of endpoint (backfat thickness, slaughter age, and slaughter weight) from 1,746 animals by 170 sires were analyzed. Failure to oinclude a term for sire by region by year-season interaction in the statistical model resulted in what appeared to be inflated estimates of heritability for all three carcass traits. Choice of the slaughter weight endpoint compared to fat thickness and slaughter age endpoints reduced the estimate of heritability for marbling score but increased the estimates for dressing percentage and ribeye area. The choice of endpoint also affected estimates of the genetic correlations among the carcass traits. Generally, estimates of genetic parameters from analyses with backfat thickness and slaughter age as endpoints were similar but were different from estimates from analyses with slaughter weight as endpoint covariate. The implications of different estimates of heritabilities and genetic correlations with different endpoints are not clear.
Technical Abstract: Data (n = 1,746) collected from 1985 through 1995 on Korean Native Cattle were used to estimate genetic parameters for marbling score (MSC), dressing percentage (DRP), and longissimus muscle area (LMA) with backfat thickness (BT), slaughter age (SA), or slaughter weight (SW) as covariates. Four models were used to obtain estimates of genetic parameters with REML. Mode 1 included genetic and residual environmental random effects. Model 2 added an uncorrelated random maternal effect of the dam. Model 3 was Model 1 extended to include sire by region by year-season (SRYS) interaction. Model 4 combined Models 2 and 3. Fixed effects were region by year-season and age of dam by sex combinations. For single trait analyses, estimates of heritability with covariates to adjust for BT, SA, and SW from Model 4 were .10, .08, and .01 for MSC; .09, .12, and .16 for DRP, and .18, .17, and .24 4for LMA. From three-trait analyses, estimates of genetic correlations between MSC and DRP, MSC, and LMA, and DRP, and LMA were respectively -.99, .20, and -.11 with BT as covariate; -.88, .47, and .01 with SA as covariate; and -.03, .39, and .91 with SW as covariate. Results that choice of covariate (BT, SA, ORSW) for the model seems to be important for carcass traits for Korean Native Cattle. Including SRYS interaction effects in the model for genetic analysis of MSC and DRP may be important because whether SRYS effects are in the model affected estimates of other variance components for the three carcass traits. Whether the maternal effect was in the model had little effect on estimates of other genetic parameters.