Genetic parameters for carcass traits estimated from Angus field records

Area of Science:

• Animal Genetics
• Beef Cattle Production
• Quantitative Genetics

Background:

• The American Angus Association has conducted carcass evaluations since 1974.
• Biannual sire evaluations for carcass merit rely on collected carcass data.
• Accurate genetic parameter estimates are essential for improving carcass traits in Angus cattle.

Purpose of the Study:

• To present age-adjustment factors for carcass traits.
• To estimate genetic parameters for hot carcass weight (HCW), marbling score (MS), longissimus muscle area (LMA), and fat thickness (FT).
• To refine the Angus carcass genetic evaluation program.

Main Methods:

• Animals were classified into two age classes: <= 480 days and > 480 days slaughter age.
• Linear and quadratic partial regressions on slaughter age were estimated for HCW, MS, LMA, and FT within sex and age class.
• Heritability and genetic correlations for age-constant carcass traits were calculated.

Main Results:

• Heritability estimates for age-constant HCW, MS, LMA, and FT were .31, .26, .32, and .26, respectively.
• Significant positive genetic trends were observed for HCW and LMA.
• Small but significant negative genetic trends were found for FT and MS.

Conclusions:

• Age-adjustment factors and genetic parameters derived from this study will improve the Angus carcass genetic evaluation program.
• The findings support selection for increased carcass weight and muscle area while managing fat thickness and marbling.
• Continued genetic evaluation is vital for enhancing beef carcass merit in Angus cattle.