Parameter estimates for genetic effects on carcass traits of Korean native cattle.

Abstract

Data (n = 1,746) collected from 1985 through 1995 on Korean Native Cattle by the National Livestock Research Institute of Korea were used to estimate genetic parameters for marbling score, dressing percentage, and longissimus muscle area, with backfat thickness, slaughter age, or slaughter weight as covariates. Estimates were obtained with REML. Model 1 included animal genetic and residual random effects. Model 2 was extended to include an uncorrelated random effect of the dam. Model 3 was based on Model 1 but also included sire × region × year-season interaction effects. Model 4 combined Models 2 and 3. All models included fixed effects for region × year-season and age of dam × sex combinations. From single-trait analyses, estimates of heritability with covariates to adjust for backfat thickness, slaughter age, and slaughter weight from Model 4 were, respectively, .10, .08, and .01 for marbling score; .09, .12, and .16 for dressing percentage; and .18, .17, and .24 for longissimus muscle area. From three-trait analyses, estimates of genetic correlations between marbling score and dressing percentage, marbling score and longissimus muscle area, and dressing percentage and longissimus muscle area were, respec-

Genetic Analysis of Carcass Traits in Hanwoo with Different Slaughter End-points

“…Heritability estimates of marbling score were moderate to high (0.41-0.42) from all models that ensure effective selection to make genetic changes in this trait. Our heritability estimates were similar to the estimates by Lee et al (2000). However, they estimated genetic and residual variances in Korean Native Cattle (Hanwoo) to be some less than our estimates.…”

“…This resulted in slightly smaller heritability estimates of rib eye area and carcass weight and slightly larger heritability estimates of back fat thickness. Similar trend was found by Lee et al (2000) for rib eye area or by Cundiff et al (1969) who found significant changes in the variation of retail cuts by covariating on carcass weight. Slaughter weight covariate also strengthened both phenotypic and genetic relationships between carcass weight and dressing percentage and between back fat thickness and rib eye area (negative) or carcass weight (positive).…”

“…Meat-grading technicians are subjectively grading meat quality Evaluation of genetic potential in carcass traits is in controversy. Three main focuses in modeling carcass characteristics are estimating breeding values at constant age (Hirooka et al, 1996), constant carcass weight, constant marbling score or constant back fat thickness (Lee et al, 2000;Shank et al, 2001). Proper assessment of the relationship of models in terms of genetic variances and covariances are required in effective selection of evaluation models for carcass characteristics (Cundiff et.…”

Genetic analysis of carcass traits of steers adjusted to age, weight, or fat thickness slaughter endpoints1

“…The decrease in the estimate of genetic variance for DP caused by adjustment for age or fat thickness relative to adjustment for carcass weight (0.75 and 0.70 vs. 0.89% 2 , respectively), combined with an increased estimate of phenotypic variance for ageand fat thickness-adjusted DP (3.89 and 3.82 vs. 3.36% 2 ; Table 3), could explain the decrease in age-adjusted and fat thickness-adjusted h 2 estimates. Lee et al (2000) reported that the h 2 estimate with slaughter weight as a covariate was greater than when either fat thickness or slaughter age was used as the covariate in a model that included direct genetic, total maternal, and sire × region × year-season interaction as random effects. In a review, Koots et al (1994a) did not find an important difference between weighted averages for h 2 for DP at constant age (0.39) or weight (0.38) endpoints.…”

“…The chosen endpoint should be determined by expected response to alternative selection criteria (e.g., increased retail product and increased marbling). Few studies (Cundiff et al, 1969;Lee et al, 2000;Devitt and Wilton et al, 2001;Shanks et al, 2001) have compared estimates of heritability and genetic correlations for carcass traits adjusted to different slaughter endpoints. Results from those few studies were inconsistent, although some studies revealed that heritability and genetic correlations estimates were sensitive to the covariate included in the model as the endpoint.…”