Characterizing Carcass Genetics

CHARACTERIZING CARCASS GENETICS IN CHAROLAIS CATTLE by Dr. Sally L. Northcutt, Genetic Consultant

Charolais cattle have a positive reputation of providing beef production systems the genetics that contribute to profi tability measured in our industry. The excellent early growth, strong feedlot performance and the carcass yield create demand at the feeding and packing segments of the beef business. Remaining conscious of the consumer demand for beef that drives profi t today, we focus on the genetic selection tools that users of the Charolais gene pool target to infl uence endproduct merit.

Carcass Trait EPDs by Design

The AICA National Cattle Evaluation (NCE) procedures generate a full suite of carcass trait EPDs. The models in the background for these EPDs are complex because a variety of data are contributing to the genetic predictions. The NCE procedures simultaneously combine carcass and ultrasound phenotypic datasets, pedigree, and genotypes. Genetic parameters allow the seamless integration of carcass and ultrasound contemporary groups to impact the resulting EPDs as well as available genomic and pedigree connections. In addition, contemporary weaning weight records are included for scanned and unscanned cattle to account for selection bias in the multi-trait carcass models.

Red meat yield model traits. The lean trait model generates the published EPDs for Carcass weight (CW) and Ribeye Area (REA). Phenotypic record contributions from contemporary groups in the AICA database for NCE include weaning weight, carcass weight, carcass ribeye area, ultrasound scan weight, and scan ribeye area.

Marbling model traits. The marbling model utilizes performance contemporary groups for weaning weight, carcass marbling, carcass fat, ultrasound intramuscular fat (IMF) scan, and ultrasound 12th-rib and rump fat scans.

Carcass and ultrasound traits are moderately to highly heritable (h2 range of .21 to .39) indicating that selection for these traits can be eff ective in a planned breeding program. The published carcass trait EPDs are the economically relevant expression of the traits in carcass trait units: carcass weight EPD in pounds, marbling EPD in score units, fat thickness in inches and ribeye area in square inches. Genetic correlations between carcass traits and ultrasound indicator traits (rg =.70) are strong and provide the genetic framework to make the NCE models work. Detailed genetic parameters (trait heritability and genetic correlation references) are found at: https://charolaisusa.com/genetic-evaluation.php

“Filling in the Boxes” of Carcass EPDs and TSI

Awareness of the carcass models that frame the carcass trait EPDs released from each AICA NCE update, helps answer many breeder questions. Parents of carcass harvest data and ultrasound data receive the carcass trait EPDs. Genotyped animals through the AICA system receive carcass trait EPDs. Animals with ultrasound scan results from proper contemporary scan groups that pass NCE edits will also have carcass trait EPDs. With the availability of genomic testing, breeders can capitalize on early predictions for carcass merit. That does not take away from the value of contemporary scan data on nonparent bulls and heifers meeting age window criteria.

The carcass EPDs contribute to the TSI values. If no TSI is present on an animal, the fi rst place to study is the absence of carcass trait EPDs. In the index calculations, EPDs for carcass weight, ribeye area, and external fat thickness are incorporated to address genetic merit for yield grade. The Marbling EPD is also part of the TSI component traits for a quality grade adjustment. Below is a review of all EPDs included in TSI:

The AICA membership has a long history of valuing Charolais genetics in the feedlot and packing industry. From a genetic evaluation perspective, it is useful to draw upon the Charolais breed genetic trend. Genetic trend values, calculated as the average EPD by birth year, are reported for EPDs and the Terminal Sire Index. A complete table of genetic trend values can be found on the AICA website at: https://charolaisusa.com/genetic-evaluation.php

Breed genetic trend is best displayed graphically. The following illustration captures genetic change over time for carcass weight, ribeye area, and marbling.

Carcass Data Collection and Reporting

Ultrasound performance data is an indicator trait in the carcass genetic prediction system. The actual harvest data is the “gold standard” in the carcass EPD model, and this is a good reminder for Charolais breeders to capture and report any available carcass harvest data. The current resource of phenotypic records includes 12,030 carcass harvest measures and 80,778 ultrasound scans. Phenotypes have value.

Carcass records provided by breeders or commercial producers using AICA Charolais sires can be edited to include the needed NCE fi elds for data submission to the Association. The primary phenotypic input fi elds include:

Member Code Harvest Date

Calf Tag Hot Carcass Weight

Calf Birth Date Fat Thickness

Calf Sex Ribeye Area

Sire Reg KPH (optional)

Dam Tag Yield Grade (optional) Dam Reg (optional) Quality Grade Group Code Marbling Score

Association staff is prepared to assist AICA membership in entering carcass records into the

AICA database. Contact the Association for more details.

Genetic Improvement Moving Forward

The Charolais breed has made impressive genetic improvement using EPDs and the TSI index that provides the commercial industry genetic inputs driving their programs in a positive direction. The revelation and use of genomics allow for even more rapid progress, but also further drives home the need to continue to simultaneously build the database of carcass harvest records and ultrasound records on seedstock. The reliable genetic predictions for carcass value and ultimately a positive consumer experience will further solidify Charolais as a component in genetic strategies moving forward.