Across-breed adjustment factors for expected progeny differences for carcass traits

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Beef Cattle Breeding

Background:

• Breed-specific genetic evaluations limit cross-breed comparisons.
• Existing adjustment factors for weight traits facilitate multi-breed EPD analysis.
• Carcass trait EPD require similar adjustment factors for accurate comparison.

Purpose of the Study:

• To develop and describe a methodology for calculating adjustment factors for Estimated Breeding Values (EBVs) in four key beef cattle carcass traits.
• To enable accurate comparison of carcass trait EBVs across different cattle breeds.
• To provide a framework for enhancing genetic selection for carcass merit in crossbred populations.

Main Methods:

• Utilized breed of sire solutions from US Meat Animal Research Center (USMARC) progeny data.
• Incorporated mean EBVs of sires and non-parents from breed associations.
• Adjusted USMARC records to 100% heterozygosity for crossbred progeny prediction.
• Applied regression coefficients of USMARC progeny on sire EBVs, accounting for measurement types (carcass vs. ultrasound).

Main Results:

• Successfully calculated adjustment factors for EBVs for marbling score, fat thickness, ribeye area, and retail product percentage.
• Regression coefficients varied significantly for carcass traits (1.65-2.82), differing from unity.
• Adjustment factors were derived for 11 breeds, including Angus as the base breed.

Conclusions:

• The developed adjustment factors allow for valid comparisons of carcass trait EBVs across diverse cattle breeds.
• This methodology enhances the accuracy of genetic predictions for carcass traits in crossbred cattle.
• Facilitates more informed breeding decisions for improved beef quality and yield.