Applying genomic information or DNA testing to cattle selection is the latest in a long line of methods producers have used to improve the genetic features of livestock over centuries of production. And while the technology already has some practical applications, scientists have just scratched the surface of its overall potential.
The National Beef Cattle Evaluation Consortium (NBCEC) has published a white paper titled “Delivering Genomics Technology to the Beef Industry,” summarizing the history, challenges and future outlook for using genomic information toward genetic progress in beef cattle.
DNA tests and genomic technology currently have three types of uses in beef-cattle selection. The first of these is to verify parentage of individual cattle. The authors note that determination of parentage is a critical factor in estimating reliable EPDs. Utilizing genomics for parentage allows seedstock producers to manage multiple sire breeding pastures and settle AI/natural sire discrepancies when birth dates are inconclusive.
The next practical use of genomic information is to identify markers for qualitative traits, which are traits controlled by a single pair of genes that have simple recessive inheritance. These include traits such as coat color, horned/polled and a variety of genetic defects. The authors note that the technology has saved the industry countless dollars by helping identify and manage lethal recessive traits for defects in cattle without the need for aggressive culling or eliminating entire lines of cattle. .
The third and more complex application of genomic technology is to select cattle for quantitative traits, which are controlled by multiple pairs of genes and influenced by the environment. Several companies offer tests and calculate breeding values based on genomic information for a variety of traits. The authors say the likely best use of this information is to combine it with phenotypic information in a genetic evaluation to compute genomically enhanced EPDs. Research indicates the genetic markers used to predict molecular breeding values are breed specific. The American Angus Association was the first to augment their EPDs with genomic information, but several other breeds are making progress toward that application.
In addition to the ongoing challenge of building understanding and familiarity with genomics, economic factors create resistance to adoption of the technology. Today, seedstock producers are most likely to invest in genomic testing and use the information in selection. They use the information in their marketing programs, but most of the value of improved selection will be realized at later production stages such as in the cow-calf, feedyard or packing sectors. A commercial producer who pays more for bulls based in part on genomic ratings needs some assurance of capturing the value when they sell calves, for example. The authors suggest
an economic model possibly could be developed so that cattle would be genotyped once early in life and genotypes shared among production sectors to derive the maximum value from the DNA collection and extraction costs incurred.
The report lists several areas in which genomic-enhanced selection could, in the future, provide tremendous economic benefits to the beef industry. These include:
- Animal Health – Research has shown that resistance or susceptibility to Bovine Respiratory Disease (BRD), the most important cause of disease-related economic losses in cattle, has a genetic component and is heritable. Understanding the genetic potential of animals to remain healthy and free of BRD is the focus of a five-year USDA-funded grant entitled “Integrated Program for Reducing Bovine Respiratory Disease Complex (BRDC) in Beef and Dairy Cattle.” The goal of this program is to reduce the incidence of BRD in beef and dairy cattle by capitalizing on recent advances in genomics to enable novel genetic approaches to select for cattle that are less susceptible to disease. This effort, known as the BRD Coordinated Agricultural Project, involves a multi-institutional team led by Dr. James Womack at Texas A&M University.
- Production -- The authors note that beef producers have a reliable selection tool, in EPDs, to assist in selection decisions for many production traits. However, there are opportunities to improve the accuracy in these traits through the incorporation of genomic information cattle evaluation. Ther e also is an opportunity to better predict input traits such as feed intake and efficiency. Feed accounts for approximately 65 percent of total beef production costs and 60 percent of the total cost of calf and yearling finishing systems. T
- Reproduction – Traits of the most economic value to commercial, self-replacing herds are reproductive traits including age at first calving, reproductive success, and replacement rate. The authors say these maternal traits are sex-limited, lowly heritable, and some are expressed quite late in life. Because of the low heritability of most reproductive traits and limited access to reproduction EPDs such as heifer pregnancy rate and stayability, genomic testing offers an appealing approach to provide these previously-absent selection criteria.
- Healthfulness of beef – Since the mid 1970’s the beef-consuming public has cast a discriminating eye towards beef in regard to its healthfulness. “Cattlemen can argue the validity of many of the claims against beef, and research supports beef as a healthy part of our diet,” the authors write, “however, there are still areas for improvement and selection may be a means to that end.” Studies have shown a potential for using genomic –enhanced selection to influence health-related components of beef such as minerals and fatty acid.